727 Transmission Issues

[nickc11211]

I have a 79' Scout II with 36k original miles on it and the transmission is acting a little strange. When I first start it and let it warm up for a bit I go to shift into reverse and it is like nothing happens. I can rev it up and it will start to move, but very slowly. However if I shift through from park down to drive and then up to reverse and then up to park and repeat a couple of times then reverse is fine.

My other issue is that when the truck is cold the transmission seems to shift fine when driving, but after it warms up the shift from 2nd to 3rd there is a little rev up. Not sure what is going on but any information would be helpful. I think I would like to change the transmission fluid and put in the atf that swepco sells. How much do I use and is this recommended?

 

[Scout-It-Out]

I'm sure someone smarter will come along and give you some more information... But here are a few of my thoughts.

The pump in the 727 doesn't run in park. Thus checking the fluid in neutral. The torque converter is likely leaking down over night. The pump has to fill it back up before the truck will move. Mine does the same thing. I just put it in neutral while I let it warm up, only when I'm sitting in it of course. I'm surprised yours does this with so few miles but the seals are old still. As for the 2-3 slip, all I can think of is double check your fluid level.

 

[nickc11211]

Thanks for the reply! It makes perfect sense the pump doesn't run in park. I don't drive it every day...maybe once every two weeks so that would do it. Also what about having the bands adjusted l? It's says in the manual to have it done at 35k miles and I just hit that about 3 years ago so maybe have that looked at?

 

[Scoutboy74]

Actually, if the engine is turning, so is the pump, no matter what position the selector is in. What happens with a completely stock 727 is that the fluid level in the torque converter is allowed to bleed back into the fluid pan when idling in park. This is by design. The thought behind it is to reduce engine load while idling in park. This is the same reason fluid level is checked while idling in neutral rather than park. No internal leakage that way, so you get an accurate reading. A quality shift reprogramming kit from the likes of b & m or transgo can be used to modify the valve body and thus close off the internal leak in park.
Your unit has low, original miles on it, but the extended intervals of non-usage could be adding up to a problem. The delay between 2 - d/3 raises a bit of a red flag. That isn't normal behavior. It might just be that your fluid level is a bit low. Or it might be that your front band tension is a bit slack.
Even with the low miles, given the age and hibernation factor, I'd treat this as more like a 75k mile service. Drop the fluid pan to drain most of the fluid (hella messy) change the filter, adjust both the front and rear bands, install a new pan gasket, and re-fasten the pan. Also remove the inspection cover at the bottom front of the trans case. Look up inside and hope like hell your converter has a little bity drain plug in it. If so, rotate the engine so that the plug is at the bottom. Remove plug and drain. By '79, I'm thinking the drain plug May have omitted for cost reduction reasons. Hope I'm wrong there. Otherwise, you'll have to force the remaining fluid out through the cooling lines with the engine running. Have 10 quarts of new fluid on hand. Start checking your level hawk after the 7th one is in. Get a factory service manual and spend plenty of time boning up on the info in this section before you get too carried away.

 

[nickc11211]

Thanks scoutboy74! I don't want to make any modifications to the truck at all so I will just have to try and run it more to keep the fluid from draining out of the torque converter. I own the service manual for 1975 but I just ordered one for 1979 because I am assuming there are going to be some differences. Will the manual explain exactly how to do all of this? Band adjustment, torque converter draining if there is no plug, etc.?

 

[blue smoke]

There is no plug for draining the torque convertor. The only way to really drain it is to remove it. I wouldn't there isn't that much fluid left.

You will need a special socket and an inch pound torque wrench to properly torque the band adjustment. There pressure line tests and a few other things

the 727 is fairly easy to work on but without the tools you May be better off taken it to a transmission repair shop (you will need to find out how knowledgeable the shop really is).

But if you wish to invest in the tools by all means do so.

 

[nickc11211]

Thanks bluesmoke! I think I might just buy the fluid, new filter, and gasket I want put in it and bring it to a shop. I don't have enough experience to be confident to mess with the part that makes the truck move lol

 

[Scoutboy74]

thanks scoutboy74! I don't want to make any modifications to the truck at all so I will just have to try and run it more to keep the fluid from draining out of the torque converter. I own the service manual for 1975 but I just ordered one for 1979 because I am assuming there are going to be some differences. Will the manual explain exactly how to do all of this? Band adjustment, torque converter draining if there is no plug, etc.?

The service manual...even the 1975 version will have the steps for adjusting the bands. The tools needed are an inch pound torque wrench as mentioned, or a foot pound torque wrench capable of being set at least as light as 6 foot pounds, which is the equivalent of the required 72 inch pound initial band tension setting (6x12=72). The tension screws have square heads, so you'll need an 8-point 5/16ths inch socket that will couple with your torque wrench. The head for the front band adjuster protrudes through the exterior of the case and can be accessed without having to remove the fluid pan. The rear band adjuster is up inside the case and can only be accessed with the fluid pan removed. You'll also need an open end wrench that will fit the square bolt head and either a deep socket or large end wrench to fit the big lock nut. With one hand holding the small wrench, you will keep the adjusting bolt from moving once you've first set the tension and then backed off the required number of turns, and with the other hand you will snug down the lock nut with the larger wrench. It sounds more cumbersome and complex than it actually is in practice. One of those things you just have to get in there and do in order to fully grasp the concept. Words on a screen tend to muddle an otherwise straightforward process.

Blanket statements about torque converters not having a drain plug simply aren't true. Some have them and some don't. All the 727 converters I've ever dealt with have had drain plugs. If your converter doesn't have a plug, here's what you can do:

you have a trans fluid cooler built into your radiator. There are two metal lines running between your trans and the radiator. After you've dropped the fluid pan and made one hell of a bloody red mess on your shop floor, leave the old filter in place and put the pan back on. Use the old pan gasket if it wasn't destroyed when you removed the pan. You don't need to get real fussy with pan bolt torque at this point. This is just a temporary situation. Use the service manual to determine which metal cooling line running between the trans and the radiator is your return line from the radiator. Disconnect that line at the trans side. Place a catch pan under the loose line. Dump a few sacrificial quarts of clean atf down your fluid fill tube. Have some more sacrificial fluid on hand to pour down the gullet as you go. Yes, this is going to waste fresh atf! This is a poh-boy trans flush, so you want the cheapest fluid you can get your grubby mitts on. Even generic label dex/merc fluid is still north of $4 a quart at your neighborhood o'wrongsleez. The stuff ain't cheap, and only gets more spendy as you go up in quality.

Now then, fire up the engine and shift into n. Have your e-brake set and/or wheels chocked. Having a helper on hand to either be the fluid dumper or the eyes on the loose cooling line fluid output is a good idea. Cycle some quarts through and allow the pump to push the fluid out through the open line. Hopefully, you will be seeing bright red, clean looking fluid towards the end of the flush before the gusher becomes a dribble. Now you can reconnect the line, drop the pan again and change out your filter.