The Stovebolt Site Forums The Shop Area Driveline Trying to change U-Joint on 46 4spd

I am afraid I’m in over my head᠁..on a simple U-joint replacement on my stock 1946 Chevrolet Truck, 4spd crash box.

I loosened the bell and pulled it back expecting to find bolts holding the U-Joint to the back of the transmission. Instead, they’re some kind of “clips” that I can’t figure out. What’s going on here? What am I missing?

Dltalfa,

Just a note that I cleaned up your post so the pictures in the "Attachment Manager" would display properly.

Am sure others will come along soon to offer some helpful insight.

Dan

Dltalfa,

Did a little searching on your u-joint issue. From what I have been able to see in available resources documents, it looks like your "crashbox" is from a vehicle earlier than '46.

1st picture below is a snapshot from a copy of a 1941 Shop Manual (original) that shows what a '41-'46 U-joint should look like (doesn't match up with what you have in your pictures).

2nd Picture is a snapshot from a copy of a 1933-62 Chevy Master Parts and Accessories Catalog showing what a '33-'40 Truck universal joint (lower one in the pic) looks like (matches your pictures to a "T").

3rd picture is a screenshot from a 1938 Chevy Car and Truck Shop manual that pictures (poorly) the u-joint and torque tube ball assembly and describes how to disassemble this earlier style U-joint.

Hope this provides some help on the subject.

Dan

Thanks Gdad51. It doesn’t surprise me that it’s an older gear box. But wow!! So I have to separate the U-Joint while it’s up inside the neck of the tail shaft!!!! 😮

I’m actually replacing the transmission with a correct 1946 3spd, with 2nd and 3rd synchomesh. I have a new transmission and a new 3spd U-Joint. If I can just get this one out, I should be good.

Thanks again!!

Glad it seems to be helpful!

Finding that would have been a surprise for anyone IMO. Since you are replacing the transmission anyhow, shouldn't need to worry to much about how you pry out those clips and knock out the trunnion as they won't get reused. I say that with a cautionary statement. You will need to make sure you have the entire U-joint assembly to reconnect the new 3 speed to the torque tube driveshaft and that it all fits/mates up correctly. Don't destroy or throw anything away until you make sure everything you need is on-hand for reassembly.

The '38 instructions and picture seem to indicate once the clips are out you can easily knock loose the bearing cups and trunnion with a BFH and a drift pin. Make sure you support the torque tube so it doesn't come crashing down on you or any body parts directly below as you disassemble!

Dan

My 39 3/4 ton has the same trunion/clips, but 2 trunions. Since I was taking the transmission out, I found it easier to unfasten the rear axle and slide it and the torque tube backward. I had pulled out the clips and still couldn't get the trunion to come apart.

Rick G.

Thanks Rickmg. I could do that, but I’d hate to take my brake lines loose. I just recently got them working correctly, LOL!!!

I’m going to try and drive the reunions out this weekend.

Dltalfa,
On my '42 I have had my truck up on a friend's lift a couple times to work on the tranny. As rickmg said it was easier to undo the u bolts and walk the rear axle back a few inches to remove the u joint. I didn't have to unhook the brake line to the rear wheels but took it to as far as I could. You may not need to unhook and bleed the system. Regardless, good luck with your project.
Kent

Gracious᠁᠁this transmission is going to be the death of me, LOL!! I have tried to drift out the reunions as outlined previously. However, the u-joint is actually slightly recessed inside the tail of the transmission. So, when I try to drift out the trunnion cap, it meets with the lip of the transmission tail and will not clear. I spent 6 hours trying to remove it today.

In another note, I realized today that I only have 2 transmission bolts exposed. All other 46 transmissions I’ve seen have 4 bolts exposed, holding the transmission to the bell housing. Does
Anyone know how I access the other two bottom bolts that hold the transmission to the bell housing?

They are accessed from inside the bellhousing under the clutch cover.

On my ‘52, the torque tube didn’t allow me to remove the tranny. I needed to jack up the rear and support it with jack stands from the frame so the suspension was all the way down with the wheels hanging, then jack the front of the tube up until it touched the floor before I had enough room to remove the tranny.

Thanks, Phak1. However, my first problem is, I can’t get the u-joint disconnected. I’ve struggled with it for a week now. I apparently have an older transmission with the early u-joints. I can’t get the trunnion caps off.

It doesn't appear that you have the compatible transmission bell for that type of u-joint. I marked up the pic that Dan posted to highlight the recess where the trunnion bearings have to go into. It's apparent that someone installed the engine/transmission as an assembly with the u-joint fully assembled and slid the rear yoke of the u-joint on the propeller shaft. Either that or they moved the axle back enough to clear the u-joint. There's a bolt holding the forward yoke of the u-joint on the output shaft of the transmission, which is accessed through the center of the u-joint.

I think the only way you'll get that out is to move the axle assembly back so it clears the u-joint. Sometimes you just have to bite the bullet and do what's needed.

You’re right, I’ve just gotta bite the bullet and pull the differential back. This poses another question. Is it better to remove the U-Bolts and slide the differential back on the springs OR drop the springs and roll it back out of the way? Which is the least trouble?