The Stovebolt Site Forums The Shop Area Driveline pinion gear and shaft moving forward/backward ... something not right here

Help me out on this one - from my 1946 half-ton gear swap issue:

I installed a new 3:55 gear set and after all is completed I drove it down my driveway and heard a noise when backing off the accelerator. Opened the differential cover to see the marks in the carrier from the pinion gear. What did I miss? What keeps the pinion gear and shaft from moving forward and backward???

Help me out on this one. 46 half ton gear swap issue

Your assembler made a major mistake somewhere when the new ring and pinion was installed. The pinion bearing assembly should have been retained at the correct depth in the ring gear by the three setscrews in the torque tube/carrier housing. There's a definite possibility that the new gears have been damaged as well as the spider gear carrier. Those spiral scars can be smoothed out with a sanding disc on an angle grinder, but the whole assembly is going to have to come out and be disassembled and inspected for damage to the gears. Good luck!

Edit: When I enlarge the picture I can see some chips and scars on the ring gear teeth. If the ring and pinion isn't totally trashed, the rearend will probably have a whine even if the gears are reinstalled correctly.
Jerry

Jerry I did the work myself. Followed the available online instructions to the “T”. Backlash and runout were set within specs and all was reassembled. What is not addressed anywhere I could find are instructions involving those three set screws you mentioned. I reinstalled them to the exact same depth as the original for lack of data.
I have inspected the ring and pinion gears and they are still unscathed. Just the scraping of the carrier. I went approximately 100 yards total in my test…
If there is data out there pertaining to the three set screws I would appreciate at least a link to it.
Thanks Jerry
Bob

The setscrews are installed deep enough to bottom out against the pinion bearing race- - - - -I believe there are dimples in the race, or possibly a groove for them to bottom out into and prevent the race from sliding back and forth. Ignore whatever depth the screws had before- - - -bottom them out with the lock nuts backed off, make sure the bearing race can't move, and then tighten the lock nuts. As soon as you went from "pull" to "coast", the pinion gear, bearing, and driveshaft were pulled backwards to contact the ring gear carrier. I'd strongly recommend a full teardown, inspection, and cleanup of any debris that might have been created by the gear/carrier contact.
Jerry

Below is a cross section of the rear axle and the assembly of the pinion shaft.
I think what went wrong is number 10 in the assembly instructions.
This is from the GMC 47 maintenance manual; they used the same rear end.

Yep, my instructions did not have anything like that mentioned. I’ve got the carrier out and cleaned up. Decided to replace both carrier bearings while I have it out again. I don’t suppose a guy can put it all back together properly without taking the torque tube and front differential housing out? So much work for one person laying on the ground.
I’ll then be sure to get those set screws correctly seated.

I removed the torque tube assembly and the pinion gear/drive shaft from the tube. Here’s a picture of how the shaft lines up with the three set screws. There nothing there for them to seat on!… I’m not sure where to go from here.

#39 missing?

Look at the diagram from the service manual- - - - the wedge sleeve is missing, or installed backwards.
Jerry

Jerry those diagrams are for 47-50 trucks. I have some instructional papers with parts diagrams on them for a 46 and it doesn’t show that part. Also, as near as I can tell, this rear end/torque tube assembly has never been apart.

Did you, by chance, take any pics during disassembly?

I did and there’s no other parts besides what I have.

Bob, I think these pic from a couple of my resource books (1942-46 Shop Manual and Master Parts Price List), along with an edited screen grab of your pinion gear pic may shed some light on the subject. I think you have all the parts, the bearing locking sleeve (ring) is just in the wrong place on your gear (red arrows show where your part is and blue arrows show where it should be). It needs to be moved to the forward position to press against the back edge of the front pinion bearing. Your sleeve (ring) doesn't seem to have the steep edge like in the book pictures, but the beveled tipped retaining screws just need to rest against the lip of that ring to push it forward and hold the bearing and gear in place. It doesn't need to rotate as that's the bearings job. Hope this is helpful.

Now I see it!!! That makes so much more sense now!!! I thought I’d lost something as well as my mind (again).
I am leaving on a camping trip with the grands for the weekend but I can’t wait to get back and get it together right!
Thank you!!!

Bob, Enjoy your camping trip and let us know the outcome when you get back to it.

Back on the road!!! Finally a win! All due to missing the importance of the three set screws on the torque tube assembly. Fortunately that oversight only cost me some time and a bit of polishing of the carrier where the pinion gear rubbed it.
After a proper test drive I’m completely pleased with this new 3:55 gear set change. It really was a bit of work for one person all don with the truck on Jack stands in the rear. That stuff is heavy and fights you all the way.
Thanks so very much to all of you who offered help and suggestions throughout the process. I only hope I can return the favor someday.
Bob

Bob, That's awesome news and so glad it all worked out. How about some pics of the truck out and about??? Get one of the "grands" you went camping with to take pics.

Enjoy the ride. Perseverance pays off. Great job tackling that project by yourself!

Here’s my truck. Love driving it even more now with the taller gears.
As for the grandkids, they are young and our daughter has elected not to have their images out on the web. Sorry man. 🤷🏼

Bob - No Worries. I was actually suggesting you have them take the pics of you driving your truck (or simulation there of). Thanks for the pics and very glad you are able to enjoy the truck!

BTW - I really like your bed rails!

Loved reading about your journey through the repair and love your truck! Nice job!

Resist the temptation to restore the body. It takes many years to get that gorgous patina.

Absolutely no plan to change the patina. I completely agree with you.

Moderator goes off topic (me) - What a gorgeous truck! So glad you got the rear differential issue solved and that the Stovebolter's were able to assist you. This love of old trucks and the willingness of like minded individuals to help others is , well, amazing. Enjoy!

Yep it’s been a fun transformation from a barn a year and a half ago till today. It’s just a great driver with stories I wish I knew about.
And a huge thanks again to all who gave input and assistance to get me rolling again!

Now for a sensitive subject; seatbelts or no seatbelts? I am preferring no seatbelts but now that I can zip down the road a bit faster (freeway speed!) I’m considering it.

Bob, ask your seat belt question in the Interiors forum. Lots of previous discussion on the topic in there to help you out.