Driveline Noise - Please Help

[79ihfanatic]

Ok well I grabbed some 50w and ill be changing the fluid tomorrow and inspecting for excessive wear and ill post if that helps anything. Thanks for all the input. Im soon to lose my mind if I cant figure this out... But at least the radio covers it up

 

[Scoutboy74]

Good call. Just don't expect a fluid change to make the noise go away. This is merely one of those house keeping things.

 

[79ihfanatic]

Yeah I really dont expect much to happen but ya never know. Every now and then I get a lucky day

 

[79ihfanatic]

Yeah that def did not do anything. Im going to put it on stands tomorrow and try running it up to speed and try and pinpoint the noise. Pretty sure its the t/c bc if I slightly pull on the shifter back towards the 4hi position the noise intensifies. So maybe a shifter fork adjustment? Would it hurt anything to pull the pan on the t/c and leave it off to run it up to speed on stands so I can see whats going on in there? Will it hurt the gears or anything not having oil on them for just a min?

 

[Michael Mayben]

There is no "shifter fork adjustment" on d20 shift assembly. However, the shift forks are retained to their rails by set screw.

Running the case with the pan off for just a short time with the rig on stands won't really put any load on it, so what you propose would be acceptable. It will throw much lube residue out though, so keep your face away from the opening!

 

[79ihfanatic]

Ok so I did that and it seems to be the transfer case. Specifically the rear output gear and the intermediate gear are chattering bc it appears that there is slack in them. What could cause this? Rear output bearing?

 

[79ihfanatic]

Ok so here is a video of the noise im hearing through the floor while driving. From what I can tell its coming from the meshing of the rear output to the intermediate gear. There is alot of slack in the gears

youtube - Dana 20 internal

 

[Scoutboy74]

Cool video. I've never seen that before. Not a good sounding noise. Mm can tell you better, but my .02...that case needs to come out for an inspection and overhaul.

 

[Michael Mayben]

That case is going to need a major overhaul.

The intermediate gear runs on a shaft with a set of loose roller bearings at each end. "fretting" wear on the shaft (and inside the intermediate gear) lets the gear chatter when it kinda "cocks" out of plane during rotation when loaded/unloaded, there are also thrust washers at each end. It's very common to have to replace the intermediate gear shaft due to a badly worn condition.

The front and rear output shafts run in tapered roller bearings that must be properly shimmed when rebuilding.

 

[79ihfanatic]

Well I replaced all the bearings including the needle bearings and the thrust washers. The only one I did not replace was the rear output larger bearing bc I couldnt get it removed from the shaft. That bearing was a timkin and seemed to be ok but I could have been wrong. The problem with the gear chatter remained the same before and after the rebuild. The intermediate doesnt seem to move at all on the shaft and the old roller bearings didnt seem to be in any different condition that the new ones. I will post pics of the rebuild and of the gears maybe you can tell me if they look too worn.

 

[79ihfanatic]

Here is some pics of what im workin with

 

[79ihfanatic]

Ok so I was going back through my pics of the rebuild and I May have found maybe my issue? Is the rear sliding gear supposed to be so loose on the rear output shaft like this? Just doesnt look meshed right.

 

[Michael Mayben]

I can't tell from your pic how "slack" (backlash) the sliding gear might be on the spline of the rear output shaft. It should be very snug but still free to slide of course!

This pic is a d20 I have on the bench now for rebuild, an earlier twin stick unit circa '68 or so behind a t-18 trans. It has no backlash but will slide smoothly when the shift lever moves the fork.

The rear output shaft is supported only in it's companion tapered roller bearing which has it's end-play/preload adjusted by selective shimming. So the output shaft should have no lateral or in and out movement whatsoever. The rear sliding gear is supported only on the splines of the rear output shaft.

 

[Michael Mayben]

This is the relationship of the rear output shaft, the rear slider gear, and the bull gear on the bench. There should be at least 0.030" distance always between the dog face of the bull gear (when torqued in place on the tranny output shaft) and the polished surface of the rear output shaft, if they touch or are pushed together when the case is mounted to the trans, then extreme heat due to friction will result and much noise! In an extremely hard contact sitch, the gear will turn blue from heat and the rear output shaft bearing will fail.

 

[Michael Mayben]

Let's verify that your bull gear is a proper match (helix angle) to the installed intermediate gear.

Turn the intermediate gear slowly and look where I have the pointer, you will see the Dana/spicer part number stamped in the face of the gear, you will have to use a flashlight to find it and possibly an inspection mirror if the case is still assembled.

The p/n is 2 digits separated by a hyphen, then 1 more digit, another hyphen, and then 2 digits. This number is stamped into the gear and is not a number that appears to have been part of the forging die for the gear blank. The same blank is used for many individual gear part numbers.

 

[Michael Mayben]

Here's the actual intermediate gear on the bench with a typical spicer part number shown, this part number is not correct for your case so disregard what you see, only note the location and post your part number for proper match-up identification.

 

[Michael Mayben]

This is a typical "bull gear" with the spicer part number shown. Post your bull gear part number and let's see if it's a proper match to the intermediate gear helix angle!

Since you posted that your transmission/transfer case combo is a tf 727 (in ihspeak, t-407) combined with a Dana 20 transfer case, there is only one correct intermediate gear/bull gear combination that has a properly matched helix angle.

The spicer part numbers you should be using are:

intermediate gear: 18-5-16
bull gear: 18-8-56 (26 teeth/23 splines, 17.5* helix)

again, the part numbers and spline count shown in my pics are not correct for your unit, these are just samples I shot of a considerable inventory of d20 parts I have on hand.

There was only one bull gear made for use on the 727 transmission app that has 23 splines, so ya can't mix that up!

But...it's very common that the intermediate gear May have been swapped around, or that transfer case came from some other application. The wrong intermediate gear will have the same tooth count as the correct one, but the helix angle will be 20*!!!! A complete mismatch that causes noise and binding. They can be "forced" together when the case is installed onto the transmission however.

 

[79ihfanatic]

Ok I will have to pull the case and check that, with the case open and turning as in the video the noise def seems to be coming from the rear output shaft area. The case never made noise before just kind of developed and doesnt get worse or better. Also did you happen to notice the fill plug on mine is on the side of the case facing he frame of the truck? What could this case have come out of? The IH d20's ive seen have always had the fill plug on the back of the case. I got all of the bearings replaced except the one in the rear output housing. The big bearing. Just couldnt figure out how to remove it. I still have it and im gonna try this week again to replace it since I can do that without pulling the entire case. Got any advice on getting that bearing out? Thanks for all the advice so far I really appreciate the time

 

[Scoutboy74]

That side fill plug is a clue. Some years back when I knew even less than I know now, I bought a d20 case to swap in place of the one I have currently in my Scout which was popping out of low range all the time. I figured I'd just rebuild it eventually. Now this bought case was a single stick with the texas pattern, but the fill location was on the side instead of in the rear. Keep in mind I knew nothing of bull gear and gear pitch differences. I just hauled off and installed the thing behind my 727. It went together like a glove. In 2hi, everything seemed fine, but boy when I engaged 4x4, there was a good deal more vibration and noise than with the previous unit. So I started researching and discovered much of what mayben has already posted in this thread. I went ahead and rebuilt the original unit and stuffed it back in post haste. From what I can tell, that side fill plug indicates an early d20. There could very well be incongruity with your gear pitch, which will either be confirmed or disproved when you are able to pull some numbers.

 

[Michael Mayben]

The d20 shown in my pic is a "side-fill" unit. I have a freshly-built d20 on the shelf now for a tf 727 application (proper intermediate gear) that is a rear fill and came from what I believe is a '75 sii.

The 727 was not available in a Scout II until sometime in mid-1972 calendar year.

All the d20 units use a 1-1/4" idler shaft for the intermediate gear support.

So it's entirely possible that either an "early" case was partially converted to proper Scout II/727 innards (and would be correct if the part numbers match),...or an "early" case was swapped in but contains the wrong intermediate gear for use with a 727 bull gear.

I have no direct experience with the scenario trever describes (I.e., I've never "fixed" one!), but I do know of these units being mis-matched by others, and while initially the package worked ok, the noise/vibration issue developed over a couplea thousand miles and progressively became unbearable.

While the helix angle mis-match is only 2.5*, in precision gearspeak that is a huge difference!!! The "point load" of the gears is enormous!

In case you haven't already found this resource, I think it's currently the best "how-to" regarding the d18/20 case builds:

rebuilding the Jeep / IH Dana spicer 20 transfer case

Print it for reference, it has an extensive explanation of how to remove the rear output shaft/bearing assembly and how to re-install and determine the shim pack. The first time I did a d20 build it kicked my ass too until a pro showed me how not to be shy with a big hammer and a "soft" drift!

Don't despair, even if a gear mis-match is not your issue, you would never have discovered the bogus driveshaft issue until it failed...possibly at 70mph on the highway and could have resulted in major disaster if the shaft left the scene!

I'm leaving here soon to go pick up the fresh-fabbed rear driveshaft for my truck (24 hour service for a fresh build!!!), inna long visit with the driveshaftdude Monday, I learned stuff from him regarding "drivelines" that I'd never been taught over the last 40 years! More to come about that in this thread:

http://www.forums.IHPartsAmerica.com/readers-rides/2945-beaters-third-life.html