VCCA Home Forums TECHNICAL - GENERAL Mechanical - Engine, Trans, etc Transmission removal questions

So I’m removing the transmission from my 41 AK truck today. The motor came out of a car but I’m assuming that the transmission is still the original 1941 unit. I’m a little confused on the guide pins. The service manual says to pull the top two bolts on the housing and install the guide pins. I’m assuming they are the same thread as the bolts that are removed. How long should they be? So the transmission slides back on these pins and slides forward when reinstalling? I saw a pic in another post where the guy made his own pins and cut a slot in them to tighten/loosen them with a flathead screwdriver. It seems the length is critical as too short and they won’t clear the clutch housing and too long and they will not allow removal. I’m also not sure what the torque tube is that everyone mentions is very heavy and should be supported. Is it in front of the driveshaft or is part of the driveshaft? Thanks for any advice.

I didn’t mention it but the motor is a 1954 235ci.

Your truck has what is called an enclosed driveshaft. The torque tube extends from the rear of the transmission to the front of the rear axle assembly.

Just like you mentioned, I made my guide pins by cutting the heads off of a couple of fairly long 1/2” cap screws. The length is such that about 2” is exposed when I thread them into the bell housing with the transmission installed. I do bottom the thread in the bell hosing so the transmission is sliding on the unthreaded portion of the bolt. It slides a lot easier. I can’t remember for sure but I think I also cut some of the threaded end off so I did not have to thread as much through the bell housing.

The 2” allows you to slide the transmission back far enough to pull the input shaft out of the clutch splines most if not all of the way. The torque tube does need to be dropped far enough that it is below the transmission when you slide the transmission to the rear.

Thanks. That helps a lot. I have everything loose now but I need to Jack up the rear of the truck to drop the axle so that hopefully the torque tube will slide out far enough to drop out of the way. It should slide out correct?
Thanks.

You should be able to slide the bell shield that covers the u-joint quite a distance to the rear. It might help,to loosen the seal collar slightly.

That exposes the u-joint so you can separate it after removing the bolts. Then slide the rear half of the u-joint to the rear.

When you raise the truck and let the axle drop that whole assembly should move to the rear as the axle drops. That is when you have to be ready to support the torque tube.

Thanks for the help! I ended up having to remove the cross brace since I couldn’t slide the torque tube far enough back to clear the transmission. The u-joint seemed to have a little play in it, is that normal? I need to figure out which transmission I have now. I’m going to try and post a picture and see if anyone can ID it for me.

Here is the transmission. Any idea on the make and model.

I believe that the 1941 shop manual states that the cross member should be removed for most cars and all trucks. The exception is the cabriolet.

I agree that the reference to that step for trucks is a little nebulous. The manual states that all service operations for the truck transmission are the same as passenger cars except for the shifter assembly.

Thanks for the help. I just need to ID the transmission for parts. I sent the pic to a transmission guy in Phoenix. He works on a lot of 60’s and 70’s stuff and he wasn’t familiar with mine. I think Chevy used the same 3 speed tranny from 37-54 but who knows?

Take a look at the pictures in the shop manual and the Master Parts List. At first glance it appears that is the original 3 speed for your truck.

There was a lot of commonality in the 3 speed transmissions over all those years. There were minor changes year to year that might be relevant if you are replacing parts.

What is wrong with the transmission?

It’s leaking pretty bad from the top shifter area. Going from 2nd to 3rd requires a double clutch to prevent grinding and from 3rd back into 2nd always grinds even if double clutching. Occasionally jumps out of 3rd. The shifter is really sloppy. When going slow in 1st gear, the truck will start lurching, eventually getting pretty violent. This only happens at a steady slow speed in 1st and not while accelerating I usually push the clutch in for a second or two then let out the clutch and it smooths out or just simply shift to 2nd which doesn’t do this. Not sure if this is transmission related. I noticed the aft rubber bushing in the mount that attaches the transmission to the cross member is pretty worn and that could be contributing. I thought that was a Muncie transmission but I’m not sure now. Did Chevy make their own transmission?

The “ lurching” in first gear could very well be due to bad mounts, all 5 of them.

It does sound like the transmission needs internal work, most likely synchronizers.

I suggest that you show the shop manual to your transmission mechanic. That will help him determine if he wants to try to rebuild it.

Parts availability might be an issue, especially worn shifter related items. You might need to get some of them rebuilt by having the worn areas built up with weld and then machined/ground back to size.

Luckily, I found an older gentleman in a local transmission shop that has worked on old manual transmissions quite a bit. I’m taking it in on Monday.

My aft transmission mount is badly worn. The rubber has deteriorated since a lot of oil has leaked onto it over the years. Looking at some of the vender websites, almost every one has one in their catalog bit out of stock. Has anyone ordered one of the rebuild kits and have any success? My truck is a 1941 AK but the mount for a 1937-1939 looks a lot like mine.

I cannot offer guidance about the rebuild kits.

I suggest that you review page 170 of the 1941 shop manual. It has excellent information about the drivetrain mounts.

I would bet a cold beverage that the front and side mounts are pretty well shot also unless someone just recently replaced them.

Thanks. I’ll check that out.

I reviewed pg 170. I’ll check out that measurement when I get it put back together. I’m having to make the rubber mounts on the aft transmission mount. I found an old piece of conveyer belt rubber that is exactly the right thickness and it seems very durable. I have it all cut to fit, I just need to go to Ace Hardware and buy two bolts with nylon locking nuts and washers. It seems the bolt needs to be tight with no play for the mount at all. So the rubber mount is supposed to isolate vibration and shouldn’t move at all right? I’m hoping this new mount will cure the lurching I had in first gear since the old one had a lot of play in it.

While the conveyer belt will give you the right thickness it will probably not isolate vibration.

You need to check the other 4 mounts. The shuddering is the result of the whole drivetrain moving around when torque is delivered.

The four motor mounts have been replaced about 10 years ago and look good. The transmission is a GM manufactured unit. Waiting on the shop to finish it up, hopefully soon.