Torqueflight 1-2 and 2-3 shift points

[Jesse B.]

I am in the process of having my 727 rebuilt (2nd time) and have a question about the 1-2 and 2-3 shift points. When it was rebuilt the first time I was not happy with the shift points at wide open throttle (wot). With 3.54 gears and 32 inch tires my tranny would not shift into 3rd gear until 60 mph (which according to my IH manual is close to oem spec). My 304 was screaming at that rpm and it did not have anything left to give. I tried several times to lower the shift points by adjusting the throttle pressure/kickdown linkage, but to no avail. I could obtain a slight difference (a couple of mph difference) but not enough to be really helpful, and it would negatively affect when the engine would kickdown.

I have been reading a torqueflight rebuild manual and it explains that governor weights are the most important element in shift points. Has anyone tried to modify these weights or perhaps use other methods to change their shift points at wot?

Thanks,

 

[Michael Mayben]

My opinion is...that failed transmission was simply not setup correctly. There are many adjustments to be made/verified on a stock valve body alone. And the shiftpoint tables in the service manuals are not "exact", those are a simple guide only, every tranny and every vehicle is gonna be different.

If working with the throttle pressure control previously had little effect regarding upshift points, then that is a real clue that the valve body needs attention.

If the valve body in the failed tranny did not have the "partial throttle kickdown" add-on module, then you must apply full throttle under "normal" load conditions in order to initiate a 3>2 downshift under load. Review post #38 in this thread for an explanation of that feature:

http://www.forums.IHPartsAmerica.com/transmission-tech/1315-t407-tf-727-band-adjustment.html

I never have, and never will scruu with the governor weights inna tf 727 other than to verify operation, clean, and re-install. All that modded governor weight crap is drag race stuff that has nothing to do with the real world of rv/street/trail drivability. 90% of all the stuff you find on the 'net and in the mags is in regard to the drag race app of these units, that does not translate to what is best for street/trail!

Simply installing a transgo tf-2 kit and then making the correct adjustments in the valve body once the shift improver kit is installed works wonders.

Your description of your shift points is certainly within the range of "normal". Wot 2>3 upshift on my tow rig today is 64mph either with or without the trailer following behind (6300lbs. Average gross). It is a "rv built" trans with a tf-2 kit, been hammering aways under gross load conditions now going on seven years/43k+ miles, serviced twice in that time frame. And that is 64mph as read on the gps, not the speedometer (which reads 54mph).

 

[Jesse B.]

Hi michael,

this did not come out of a magazine or from the internet. It came right out of carl munroe's book "how to rebuild or modify chrysler's a-727 torqueflight for all applications."

pages 174-175: "the shifts 1-2 and 2-3 shift points are controlled by several factors: the calibration of the governor, line pressure, throttle pressure, 1-2 shift valve spring pressure, and 2-3 shift valve spring pressure. By adjusting these variables the automatic shift points can be changed to better suit the application. Of the above variables, the governor is the most critical. The governor 'governs' the rpm at which the transmission will upshift and downshift, within the calibration of the shift valve springs, throttle pressure, and line pressure. Basically, the lighter the governor weights, the faster the output shaft needs to spin to increase governor pressure. A stiffer governor spring has a similar effect. Remember that governor pressure acts on the shift valves and also against thottle pressure. With a governor that requires a higher rpm to achieve enough pressure to move the shift valves against opposing throttle and spring pressure, the shift points go up. The 1-2 and 2-3 shift points can be altered as well by changing the tension of the shift valve springs. A lighter spring lowers the shift point by lowering the opposition to governor pressure; a higher tension spring raises the shift point by increasing the opposition to governor pressure."

as he states, throttle pressure does influence the shift points, but it would appear not as much as the governor. And honestly, I don't like adjusting the throttle pressure to drop the shift points because then that also drops the point at which the transmission will downshift. I could have shortened the kickdown linkage as much as possible to drop the upshift point by a few mph, but by that time the transmission would downshift at very low engine rpm. I would gain progress in one direction, only to sacrifice it in the other. There must be a better and more direct way to accomplish just the lowering of the upshift at wot.

The upshift point May be within factory specs, but it seems too high. For example, if we assume my second gear ratio is 1.45:1, with 3.54 gears, 32 inch tires, that engine is turning at over 3500 rpm at 65 mph (the speedo shows 60, but the speedo is about 10% off). This is almost that engine's redline. I see no reason to bring the engine up this high, especially when both the horsepower and torque curves are dropping off at this rpm. I can feel the engine just flatlining at this rpm. It has nothing left to give and seems to take forever to go from 58 to 60 mph (on the speedo).

Wouldn't it be more direct to install heavier governor weights, or perhaps lighter springs? Thanks,

 

[Robert Kenney]

. this is almost that engine's redline . I see no reason to bring the engine up this high, especially when both the horsepower and torque curves are dropping off at this rpm . I can feel the engine just flatlining at this rpm . it has nothing left to give and seems to take forever to go from 58 to 60 mph (on the speedo) .
[/quote ]

Jesse,
a wot shift point idealy should occure at or just a bit past the peak hp point and for your 392 that is about 3500-3800 . the up shifted rpm should be at about the engines peak torque or just a bit below but that is greatly a factor of gear sets . so 2000 would be about the lowest you should end up after the upshift . the above is only a wot regime where max performance is required .

the part throttle shifts are up to the driver really or at least should be . I like to keep the engine as low as possible and maintain a constant acceleration curve that allows the engine to stay happy . I guess this is where the opinion lies . I hate a late low/part throttle shift where the torque curve is diminishing long before the upshift .

I am not knocking your tune up but if it is going that flat at 3500 you May want to see if the wot afr's are fat as that will kill top end hp . the other thing I would do is set max total to 34-36 degrees if you have not already then see if it helps.

 

[Jesse B.]

Hi Robert,

actually, I am still talking about my 304, which is on an engine stand in my garage. I only got nine miles on my 392 before the transmission went on permanent vacation. (the 392 runs great, so far at least. It purrs like a kitten and has a rock solid 18.5 inches of vacuum at an idle.) since it was still fresh, I never rapped it out to see what it could do. So I am basing this on the behavior of the 304, but since the 392 and 304 have similar redlines (in fact, if I remember correctly, the 392 has a lower redline than the 304, but I would have to check the manual which I don't have in front of me right now) I did not want to have the same problem with the 392 as I had with the 304.

As far as shift points go, according to my computer dyno, my 392 setup is supposed to produce peak torque at 2000 rpm, and peak horsepower at 3500. For your reading pleasure, I attached the print out. (I do attach it with trepidation that someone (not Robert or michael) will post up with some comment about peak horsepower. So, please take note: the engine was not built to produce peak horsepower; it was built to idle smooth and produce low-end torque, so save your comments on how your 345/392/350 or whatever produces xxx horsepower, because frankly I don't give a damn. Peak horsepower does not reflect idle quality, gas mileage, throttle response, or drivability, so I am not interested. In fact, it usually impairs each of these. Share your bs with people who don't know the difference.) even though peak hp is at this rpm, I am not too thrilled about hitting 3500 to upshift. These IH engines howl at that rpm, almost like the sound coming out of an engine room in the hold of a ship.

Of course, one thing I have not considered is that I had to floor that 304 to merge onto the freeway, otherwise I'd be pushed off to the shoulder. I would expect with the 392 that this will not be a problem. So perhaps I should stick with the factory shift points? I guess I would feel more comfortable if the shift points were just dropped a touch.

 

[Robert Kenney]

Ok, now I get the whole picture. sounds like you hit the Mark on the 392. I think with your expectation and desired performance envelope, the stock trans calibration is going to be close but like anything with many variables you pretty much have to try it.

Like you said with the 304 you had high manifold pressures/throttle positions to attain the freeway on ramp gitup and go with the 392 the same acceleration will take way less manifold pressure /tp so shifts will occure earlier. With the throttle potition adjustments already built in to your tf727 you should be able to get right on the money. Using you numbers from a earlier post 2>3 upshift at 60 mph and 3600 rpm is = to 58 rpm/mph so 4 mph is 233 rpm of adjustability availible with the throttle position rod. Pretty close to where you want to be??

 

[Jesse B.]

Yeah, I agree with what you are saying. The 392 is going to have to be tried out before I will really know how it will behave and how it will influence shifts at wot. It May be that this problem is going to largely take care of itself because I won't have to floor the truck to merge on the freeway anymore (hopefully).

(btw, I remembered to bring my IH manual today and I'm looking at the engine specifications section. The factory redline for the 304 is 3900 rpm, the redline/governed speed for the 345 is 3800 rpm, and the redline/governed speed for the 392 is 3600 rpm.)

when it does come time to floor the truck, perhaps when I am passing a semi on the freeway or what have you, I am still going to need the upshift points correct. If the transmission is set up to upshift at 3500 at wot, then that May be too close to the 392 redline and the engine May flatten out by that rpm. But I won't know this for sure until I can actually get another tranny in the truck and I can drive it. As you say, if I can drop it 233 rpm by adjusting the throttle pressure, that should help, but I just don't want to run into the trouble of the engine downshifting with every slight punch of the throttle. That would make the truck undrivable.

At this point, I feel like I'm , but I'm still leaning toward having the shift points dropped in the tranny. Obviously, if it goes too far, I can adjust the throttle pressure to kick in later. I understand that michael is on vacation somewhere, so he May have more to say when he gets back. Thanks,

 

[RobertC]

Though I have no experience with tf (my t/a has a t-34 5sp od), but I would like to make some observations on the general operating characteristics of IH engine -- which I think relate to the shift points of an IH tf (not a chrysler tf).

From what I have seen posted, you can run an IH truck at max rpm "all day long". No, I would not want to do that or even close to it (why I have a t-34).

Max torque on a stock 392 is 2800 rpm.

When I took delivery of my t/a, the IH salesman told me not to run my t/a below 2000 rpm. And, the drivetrain "complains a little" if I do in 4th / od.

I have attached a page from an 1972 IH t/a trailering brochure. A graph shows the shift comparison between a 4 sp and a 5 sp (t-36 direct) -- it also shows the engine being run to "max recommended rpm" and when a shift occurs the rpm drops to about 2000 rpm exactly what occurs in my t/a).

So, I see no problem with a tf that shifts from 2-3 (or even 1-2) at 3500 rpm at wot. I would say that it was designed that way.

Another "small issue" to think about -- the original tire diameter (stock) on your Scout was probably in the 27 1/2 - 28 in range.

Btw, my 392 does not "flatten out" going to 3600 rpm -- wot or 3/4 throttle (just takes longer to "get there"). The only time I really use wot is in 3rd going "up" freeway ramps -- do not use it much in 4th, but it depends on traffic and the length of the ramp.

So, I would have to agree with robertk that your 304 "flattening out" is possibly carb "set up" problem -- Rich or lean, robertk knows much more than I do...

Hth

 

[Michael Mayben]

We're home now.

Jesse, I fully agree with the information in the munroe reference...but that stuff is in regards to drag race stuff, that entire section is based upon that...and for engines that develop much more hp/torque than any built-for street/trail IH sv motor. Those motors need heavy tranny mods in order to operate correctly...and, they are installed and run in vehicles that are far lighter than any oem or modded Scout II and are purpose built for only one purpose!

What you have experienced with the 304 and it's companion transmission is an anomaly, not the norm. You have/had a performance issue regarding the package. Ya simply can't compare that with what you will see in the future! If this shift point/rpm/road speed deal was engineering problem, then all vehicles of a similar production form would have operated the same. And all 727 trannys that have been rebuilt correctly in the past would have simply continued in generating performance complaints.

I'll not comment on "how" your failed tranny was built as I've not torn into it for a diagnosis! But without a teardown, there is no way to determine what happened and why. Can parts undergo catastrophic failure for no apparent reason? Of course they can, otherwise us mechanics would have nothing to do! But...compare the service record of the torqueflite family over the years with the same information regarding a 700r4, th400, or th350...look at all the "fixes" that have been developed by the aftermarket for those transmissions to live just behind a wimpazz v6 GM or 305 sbc motor, then look at the same for a 727! One supplier catalog I use daily shows 50+ pages, hundreds of individual upgrade parts and "fixes" same catalog shows approximately eight individual fixes spread over 20 years of tf 727 (does not include the 518 and later crap) on six pages. And out of all those individual "upgrades", five of 'em are addressed with the installation of a transgo tf-2 kit.

And when using a heavy rig for off-road or trailer towing apps, ya use the transmission gear selector lever to make it do what ya want it to, the "normal" auto-shift routine goes out the window!

A valve body that has had a shift improvement system (so-called "re-programming") will allow an infinite amount of tuning, it does away with overlap/slip, greatly reduces heat production, and adds much in the way of operator controllability. Don't like the way the "autoshift" function works, then shift it manually all day long, a 727 loves that kind of treatment.

Just did an 1100 mile pull with a gross load of about 11.5k lbs. This trip (well under normal cross country loadout). Only on the flats do I let the tranny have it's head...on the myriad ups and downs along hiway 101 and crossing the coast range it gets manually-shifted, that helps fuel economy and reduces wear and tear on the brake system. Same as when running a manual trans.

And this current toad setup has seen 23k miles operated on "roads" ranging from both doubletrack off-road trails all over the kali-desert, to nearly every freeway in the bay area, lalaland, phoenix, dfw, salt lake city, san antonio/austin, and up to mountain passes of 9.5k ft. And all the godforsaken "interstates" in between.

And with a properly tuned engine, a purpose-built (rv/towing use) 727, any IH vehicle can experience the same...even with a 304 which is really I feel the "best" truck engine.

As for an unplanned "downshift"...again, that is big part of why the "partial throttle kickdown" module was developed for the 727...that allows the trans ratios to better match engine rpm/load. With a non-partial throttle kickdown module, the throttle must be wot to effect kickdown under most conditions (but not all). That partial throttle deal went hand in hand with emissions and fuel economy "improvements" at a time in automotive history when overall drivability of all u.s.-production vehicles for consumer use was at an all time low. And if ihon is gonna work with ya on the valve body upgrade, then we need to know "which" valve body is gonna be used before a plan can be finalized. I have no preference for one over the other for any use.

Again..you are talking about a totally different engine (that hopefully does not have any drivability issues), along with a totally different transmission. No way you can compare "before" and "anticipated after" until ya got something to compare! Your former drivetrain package was broke, hopefully the new package wont' be...and if it is, then ya simply make it right!

 

[Jesse B.]

Thank you for all the input and everyone is correct, we are talking about two entirely different engines and transmissions, as even I have pointed out. I simply wanted to address what I saw as a shortcoming in my other transmission. Other than this problem, and a couple of other small issues, the tranny worked great, and I was happy with it (up until the point it broke). And since I am going to be spending on this new transmission and transfer case combo more money than what some people spend on entire cars, I want to make sure I don't have the same problem with my new transmission. I am not comfortable with hoping and praying in silence that the new transmission will be better. So I greatly appreciate everyone's patience in letting me air this out.

Based on what I've heard so far, my shift point concern May stem from problems with both the 304 and tranny. While I am skeptical there was a mechanical Problem with the 304 (the original owner took great care of the truck and had receipts dating back to 1975 when he bought the truck. Nearly all the service on the truck was performed at the dealer.), I do know it was tired. A run on a chassis dyno right before I took it out only produced 102 horsepower at 3700 rpm (a/f ratio was ideal through the pull). I should not have this problem with the 392.

I think the tranny is a different story. Since I was having trouble with the tranny downshifting too early when I increased throttle pressure (shortened the rod), I probably had a part-throttle kickdown valve body. Whether the part-throttle feature was the problem or something else in the valve body, or a combination of both, I do not know.

Since I have heard rumors that michael May be putting together the valve body for my transmission, I wonder if he could elaborate on the advantages or disadvantages between the part-throttle and non-part-throttle valve bodies. The munroe book has a little bit of discussion but not much. I know you wrote you have no preference, but I'm sure you have an opinion on both. Right now, I am leaning toward the non-part-throttle to get away from the problem I was having with my earlier tranny, but I'm not sure what else I will be giving up. Thanks,

 

[Michael Mayben]

My personal opinion...the "part throttle kickdown" was a workaround for emissions engines with decreased power output, taller gearing, and the clamor for increasing fuel mileage.

And obviously, since IH apps had that feature phased in rather late in the game, it was forced upon them as part of the deal for transmission supply. The big numbers in use of those trannys were in chrysler and amc stuff.

The main thing folks are interested in regarding the valve body difference is..."will it increase my mileage"?? And I'd say...no. That is simply not a significant change and certainly not something worth spending money to deal with, no payback for that.

Contrary to what many have spit out regarding the IH versions of the 727, they were not any different than the versions such as used behind a 383 or 440 in a fullsize passenger car. Yes, as you can see in the munroe book, there were many variations produced for chrysler based upon engine/gearing, and vehicle weight/platform. Not so for IH.

The only difference between the chrysler units and the IH units is in the output shaft design/tailshaft/tailshaft housing depending upon if divorced or married t-case...or motorhome chassis, the shape/pattern of the bellhousing, and the shape/length of the shift lever mounted to the valve body.

An oem Scout II 727 would have been produced to the same spec as the "383" shown in the chart on page 14 of munroe. You cannot determine anything regarding "how" an oem tranny was assembled by using the IH parts list, only thing that matters is what ya see when it's gutted. You can see many references in the parts list to "as required"!!

I have several core valve bodies that I can use for your application I've discussed with Jeff. All are the "full throttle kickdown" variation. I have no partial throttle units on hand. And I need to know if you want the "shift command" feature enabled on the transgo installation or not. Doesn't mean you must use that feature, just means it's there. I do not advise enabling that feature if anyone else is going to drive the rig...it's not something to be treated lightly...kinda like disabling the nss system!

 

[Robert Kenney]

we're home now.

Mm,
glad your back!! Hope the beaches were nice.

Jesse, I fully agree with the information in the munroe reference...but that stuff is in regards to drag race stuff, that entire section is based upon that...and for engines that develop much more hp/torque than any built-for street/trail IH sv motor.

Jesse you already know this but if mm is seting you up you will be happy for sure.

Buuuuuut michael.......... Kinda sounds like you got sumpin sour regarding drag racing..

the gigolo thinks so too.

 

[Michael Mayben]

mm,
glad your back!! Hope the beaches were nice.



Jesse you already know this but if mm is seting you up you will be happy for sure.

Buuuuuut michael.......... Kinda sounds like you got sumpin sour regarding drag racing..

the gigolo thinks so too.

Beach was kool...but ft. Stevens ousidea astoria was really kool!

No problem with drag racing schnizz...for drag racing! It dam shore what I lernt on!

But 90% of all the slushbox tranny stuff and parts that are pimped all over the place are drag race parts and concepts...not any real application for street/trail! Much of the band and clutch systems used are "ten runs and they are toast" kinda items...fine for 10 runs and then a teardown. But that stuff just doesn't work inna tow rig/dd/trail rig.

Who woulda have ever thought in 1968 that the lowly powerglide which was a pos to begin with, would become the mainstay in drag race use as it is today! But of course, those trannys bear little resemblance to an oem powerglide. And I just can't see a transbrake being an advantage regarding those metered freeway ramps in yore kuntry! But then...maybe the gigolo would be the hot tikee for a metered ramp launch???

All I'm preachin' is ...drag race stuff is for drag race...and rv/towing tranny build is for for street/trail stuff...two different worlds!

 

[Jesse B.]

Hi michael,

I assume you mean the "tf-3" version of the transgo package when you are talking about the "shift command" feature? If so, then no, I do not want that. I would like the tf-2 installed in a full throttle kickdown valve body instead. If you are talking about something else, let me know. Thank you, and everyone else, for all of your help.

Last question, since I am going with a new tranny, I think I should get a new torque converter as well. I don't want to contaminate my new tranny with pieces of junk from the old one. Any suggestions for the correct torque converter for this 392 application?

 

[ihpartsjeff]

hi michael,

I assume you mean the "tf-3" version of the transgo package when you are talking about the "shift command" feature? If so, then no, I do not want that. I would like the tf-2 installed in a full throttle kickdown valve body instead. If you are talking about something else, let me know. Thank you, and everyone else, for all of your help.

Last question, since I am going with a new tranny, I think I should get a new torque converter as well. I don't want to contaminate my new tranny with pieces of junk from the old one. Any suggestions for the correct torque converter for this 392 application?

The tranny that I would like to sell you already has a rebuilt convertor in it. Not sure what size or specs but I probably can find out. I would not even consider putting the convertor out of the old tranny into the new one - never.

 

[Jesse B.]

the tranny that I would like to sell you already has a rebuilt convertor in it. Not sure what size or specs but I probably can find out. I would not even consider putting the convertor out of the old tranny into the new one - never.

Thanks Jeff.

 

[ihpartsjeff]

thanks Jeff.

If you want a custom torque convertor for this just say the word as I can always use the existing convertor for another transmission.

 

[Jesse B.]

if you want a custom torque convertor for this just say the word as I can always use the existing convertor for another transmission.

I don't know if one is needed. I know that torque converters are generally set up for particular displacments with particular torque profiles, but I don't know if I should use a different one with the 392. The one in my old transmission seemed to work fine behind the 392, but I was really babying it and I don't know if another converter would have been a better choice. Let's see if michael posts up. Thanks,

 

[Michael Mayben]

hi michael,

I assume you mean the "tf-3" version of the transgo package when you are talking about the "shift command" feature? If so, then no, I do not want that. I would like the tf-2 installed in a full throttle kickdown valve body instead. If you are talking about something else, let me know. Thank you, and everyone else, for all of your help.

Last question, since I am going with a new tranny, I think I should get a new torque converter as well. I don't want to contaminate my new tranny with pieces of junk from the old one. Any suggestions for the correct torque converter for this 392 application?

No...a tf-3 kit I will not install inna street-operated rig, that is a "purpose-built" valve body install only!!!!

The shif kit would be a transgo tf-2 kit. The "shift command" portion of the installation/mod enables a feature whereby the trans can be placed in first/low gear at any speed by moving the shifter to manual low/1!!!!!!

You can well imagine what might happen when that is done inadvertently at speeds above say 30mph!!!! Onna trail rig, ya could easily experience total loss of control in an instant....but it could also save yore azz inna "last ditch" mode if ya knopw what is gonna happen...I have my tranny set up with that feature...and in some serious offroad stuff several years ago where I was onna downhill where I should never have been...I had to use that little "jerk into low" scenario and it saved me from going over sheer drop into a canyon, the loose surface prevented any kind of modulated braking action, the rocks were teh size of softballs and larger with no traction at all...but engine braking saved the day.

Gotta go, we're loosing power agin inna major storm...I'll be back!

 

[Jesse B.]

All of the descriptions of the tf-2 kit describe that feature as part of the whole package. It sounds fine to me, please install.

Any thoughts on the torque converter?