The Stovebolt Site Forums The Shop Area Driveline Tranny swap preparation help

I’m about to swap the broken 3-speed tranny in my ‘50 half ton for a working one. What gaskets and other items do I need to buy to have everything I need to do the job? I plan to get whatever I need from NAPA. Thank you!

Chuck,

Just a note to try and confirm so answers to your question can be as accurate as possible.

This is for your "1950 Chevy 1/2 ton (all original)" listed in your signature line?

If yes, can we know for sure this is still the "closed" torque tube drive unit?

Are you planning on replacing the clutch/pressure plate/throwout bearing set?

Last question - Are you planning on having to open up the 3 speed you are transplanting into your truck (side cover and such) for internal check?

Let us know.

Dan,

Yes, this will be a swap in my all original ‘50 half ton. It still has the old torque tube.

I was told by the PO that the replacement tranny was good, so haven’t planned on taking off the side cover, but guess it couldn’t hurt anything. It will need to be filled with oil.

This is a temporary fix. I plan to have a shop swap the current worn out 216 for a 235 and will replace the clutch, pressure plate & throw out bearing at that time. I just want to drive my truck in the meantime.

Just curious, what's broken on your current transmission?

People can sometimes have fussy memories. I would at least pull the side cover of the replacement transmission and check it out. Take some pictures of the gears and synchros. You don't want to waste labor installing a bad transmission especially one that's attached to a torque tube drive shaft.

The side cover has a gasket. The real headache comes with replacing the seals on the torque tube which is logical to replace at this point. The seal kits are readily available at your FLAPS or stores on-line. There is a procedure to safely remove and install them. Take some time to read about it here on past Stovebolt postings. The procedure is in the shop manual. http://chevy.oldcarmanualproject.com/shop/1948_51truck/index.htm
The torque tube is directly connected to the rear axle which may have tension in the leaf springs. If you disconnect the u-joint inside the ball, the driveshaft can crack your skull. If you already knew this then you wouldn't be asking about the gaskets. Ask questions and be safe.

Which gasket kit should I purchase? There are no descriptions in the details about either one so I don’t know the difference except one kit has more gaskets. Thanks

I recognise the top gasket set (ts5100). It's for the 4 speed SM420.

So, I assume the lower set would be for the three speed.

That’s kinda what I thought Gord. I didn’t recognize anything in the 1st set, so it has to be the 2nd. I’ll order it tomorrow. Thanks Gord.

You will also have to get the torque tube bell gasket kit

Chris and I began the transmission swap this morning. We went right by the book……. disconnected the shifter linkage, rear tranny mounting plate, and speedo cable. Jacked up the rear and put the jack stands just aft of the leaf spring mounts so the rear axle was free to dangle with no weight on it. Removed the flywheel cover and the four main transmission bolts. Pulled the round ball joint sleeve as far back as it could go, then as I held up the torque tube Chris pulled the tranny away from the bellhousing. We could never get it past the end of the torque tube. So, we tried pulling the U-joint out of the torque tube so we could get it just 1/2” higher. No luck! We took a breather and went for a bite of lunch and decided that we might get the torque tube just a bit higher if we removed the access door in the floor. It looked like it had been replaced with sheet metal in years past by the PO, and the small Phillip screws were impossible to remove, and cutting out the floor panel would be my only option, so I didn’t. We attempted to remove the rear transmission support beam with a 4 lb. BFH but we stopped, believing we’d have bloody hell knocking it back in place and aligned correctly in order to install the 6 mounting bolts. It was wedged between the rails really tight. Chris packed up and left, and I put all the tools away. We thought we’d knock out the job in a few hours and I’d be back on the road, but it didn’t happen.

“If at first you don’t succeed, try, try again??”

Did you remove the u-joint ball cover from the torque tube as well? That would get you another inch or two. The Service manual doesn't mention that, but does say to use a jack to raise the torque tube.

The cab may be sagged a bit on the rear shackles, giving you less room. Maybe blocking the rear of the cab up a bit would give you enough room to remove the tranny.

[on edit] The frame is tapered (wider at the rear) at the transmission support crossmember, so it shouldn't be that hard to get out if you push it toward the rear of the truck.

Also, there's no gasket between the tranny and bell housing, so unless you're opening up the tranny (as recommended by others -and also me) all you would need is the u-joint bell gasket kit. That needs to be reinstalled off the torque tube so you can select how many gaskets you need between it and the tranny. Check the shop manual for the procedure.

My 54 with the sm420 ,I ended up taking the rear axle 4 u bolts off to get mine back that extra inch ,never had to disconnect the brake flex line just had to buy another 4 u bolts .

Kevin, we could only slide the U-joint ball cover backwards. If we could have removed the other half of the U-joint from it then we could have pushed it forward and off the torque tube.

We debated where else to put the jack stands that would still allow the rear axle to hang free. The frame was the only other available place.

We didn’t think to knock the transmission support beam backwards. We had more room to swing the hammer towards the front of the truck. Maybe we didn’t think that through very well, so I might crawl back underneath tomorrow and take some measurements to verify what you say about the frame getting wider as it goes toward the rear.

Thanks

Chuck,
Are you saying you couldn't slide the rear yoke off the driveshaft? It should slide off (assuming there's enough room.)

If you don't have room to swing a hammer from the front, use a ratchet strap around the rear axle and the crossmember to pull it to the rear. The frame rails definitely get wider at the rear. Also,there should be 5 bolts per side, 4 with nuts thru the frame web from the side, and one thru the lower flange into a captive nut in the crossmember. If you didn't get them all out, it would be a bit hard to remove, even with a bigger hammer.

You asked if I removed the U-joint ball cover from the torque tube and I answered no. Then I stated that we could not slide the rear yoke off the driveshaft because there was no room. The torque tube tip was against the floorboard and wouldn’t allowed to pull off the U-joint & yoke.

There were only 2 bolts on each side of the crossmember and one coming up from the bottom for a total of 3 on each side. I didn’t see any extra holes but will look tomorrow.

Thanks Kevin. I appreciate the help