The Stovebolt Site Forums The Shop Area Driveline 49 3100 front yoke

Do they make a longer 17 spline front yoke for these. It’s a 49 3100 with 4 speed on floor. Still torque tube rear
Thanks

Justice,

Just a note that the pictured yoke is actually the rear half of the torque tube universal joint assembly, which slides onto the drive shaft stub in your torque tube. The front yoke is the part that slides onto the transmission output shaft and should be secured with a large washer and bolt to that shaft (not shown in your pic).

After a bit of resource searching, I did find that there are some minor differences between the 3 spd and 4 spd torque tube u-joint yoke assemblies which you can see in the picture I found in our own member tclederman's web pages 3 Speed and 4 Speed u-joints. It provides a better comparison than what can be found in the parts books.

The picture doesn't give measurements, but clearly shows that the front yoke half of the u-joint assembly is longer for the 3 Speed vs the 4 Speed torque tube units.

A search of the 1929-54 Chevy Master Parts catalog shows that both rear halves of this u-joint assembly use the same rear yoke - GM# 3665768. So no difference at least in the length of the rear yoke section.

That resource also lists a different rear yoke for the 3/4 Ton enclosed front u-joint assembly as GM# 596911, but I couldn't find anywhere what the length of that yoke is to compare to the 1/2 Ton parts.

I guess the next question is, why do you need a longer yoke???

Dan

When put together it only connects with the torque tube about 1/8 to 1/4 inch. When put in gear slips out

Justice,

Your last added picture makes it look like something isn't installed correctly. Your torque tube should be a lot farther forward from what little can be seen. Can you take and add pictures showing your rear axle placement on the springs and engine/transmission placement???

Am guessing you haven't tried to install a different axle/torque tube into your truck, have you?

Dan

Pulled front yoke. It’s the yoke for a 4 speed. 4 speed tranny. Can I run a three speed yoke on here to get a little more length

What have you done to the truck to make the driveshaft not fit?

There's more to this story that might help solve the problem...

Mike B

Mike
Short story long. Original 49 frame rusted out. Bought replacement frame complete looks to be 50s. Motor and Transmission out of original frame.
Does that make more sense

Like dan stated. That torque tube bell needs to go forward quite a bit then it will engage more of the splines. Something not assembled correctly

I have not messed with rear

Is the donor frame a 3100 frame same as the old one? Or maybe a 3600 frame with a longer wheelbase that’s throwing length off? Do you still have old frame and rear end to measure and compare.

It is a 3100 frame and I really wish I was smart enough to save the old rearend but it’s gone

Just a thought, but someone could have moved the rear axle back to center the rear wheels in the fender openings.

The donor frame came with the rear end but the OP is using his engine and 4 speed. Possibly the donor truck had a trans other than a 4 speed that was different in length??

That’s what I’m wondering. Can I take the rear yoke to driveshaft place and have it lengthen or can I find a front yoke from 3 speed and put that in there

I've had driveshafts made by driveline shops before when I brought them the two yokes. Make sure you get the length needed exactly correct. It has to allow for in and out movement to allow for suspension travel, of course.

It would seem as though the longer part of the 3 speed yoke is the end into the trans. That will not help you. Just a thought on the frame........is it possible it is indeed a half ton frame, but from a GMC? They are just a touch longer.

He has a torque tube Otto not an open driveshaft.

Oh right. Too many threads with too many different trucks. I can't keep them all straight.

Justice, it seems like now would be a good time to break out the measuring tape and start calling out some numbers...

How long is your frame end to end?

What is your Wheel Base center of wheel to center of wheel?

How long is your torque tube from the face of the axle housing to the front of the driveshaft?

Did the axle get moved back on the springs by the PO?

I personally won't be able to confirm these numbers as I don't have any AD trucks, but those that do should be able to help...

Mike B

Stock 3100 shock absorbers from 50 and later trucks are mounted outboard of the frame. The OP's pic shows coilover shocks mounted inboard of the frame. So it seems like something is off.
Here's a pic of a stock axle mounting.

This is what LMC shows for the front..Rear. But the direction is off, it is because they are showing the right side here.

Justice,

As a hopeful help to go along with Mike B's suggestion to get the tape measure out and start checking your frame and wheel base measurements, you can compare your measurements to the charts in this GM Heritage Center resource document 1949 Chevrolet Truck Data.

You will find the different wheel base and frame measurements for the many different models in the early section of the document that include drawings of the trucks with points of measurement for each model.

This doesn't address the possibility that you got a GMC frame instead of a Chevy. I found this long ago thread on the GMC VS CHEVY that points out that among the difference, the front cross member/engine mount is farther forward on the GMC to allow for the slightly longer GMC I6's installation. If (?) you got a GMC frame and installed your Chevy engine (216/235/261) without changing the front cross member location, that possibly could account for your engine/transmission now sitting farther forward and no longer matching up with your rear axle/torque tube location.

Let us know what you figure out and we can try and provide more help.

Dan

This frame had 235 and 4 speed in it when I picked it up. I had my 235 rebuild and put it in with other tranny. I’m thinking switching out transmission and see. Tape measure shows other transmission longer but not easiest to measure.

LMC's diagrams are for open driveline rear axles. It's basically showing the same as the FAM Section 4 Sheet 1.00, which is 54-55 style suspension mounting. The OP's rear axle does appear to have the pivot mounts that are used for torque tube axles.

Well I solved my dilemma. Turns out this is a 41-46 four speed tranny and Bellhousings. Not quite the same. Also learned a ru and up transmission won’t bolt into the Bellhousings. Thanks for everyone’s help. As always appreciate it

Ah ... the ole Assumption Monster raises its ugly head yet again.

The reminder for all of us is this .... when dealing with used parts, never assume they are what you think they are (or want them to be). Ask questions. Confirm.

Just because it *looks* right doesn't mean it *is* right. When things that are supposed to fit don't, there's usually a really simple answer as to why not. If it isn't forthcoming, back up a few more steps until it is.



Just bringing this up as a gentle nudge to the greybeards to remember before we get carried away and head off to the fabricator shop to make things work that aren't working. Been through this myself.

Sometimes, you just have the wrong parts.

Did you slip down one row on the keyboard trying to type 47?
I'm "assuming" that's what happened and trying to help clarify.