The Stovebolt Site Forums The Shop Area Driveline ring and pinion swap on my 1946 1/2 ton

I'm about to jump into a ring and pinion swap to 3:55 gears from The Filling Station.
Has anyone done this that may have any input helpful to the process? Perhaps it's been discussed here before and I could be directed to the thread.
Thanks in advance.
Bob

Evidently not.

Bob, There is an existing Tech Tip 3.55 Gear Swap that describes the work in detail, but is directly about an AD series axle. Perhaps this will give you are starting point and others will chime in soon.

Bob,

Also, Motortrend featured an article several years ago detailing the change using a Chevs of the 40's kit. Here's the link for that.

https://www.motortrend.com/how-to/1003clt-chevs-of-the-40s-3-55-1-ring-and-pinion-swap/

Regards,

Larry

Update:
So I have the kit installed now, truck back together. The data provided by replies above was extremely helpful. But here's my problem, I took it for a test drive and all seemed great. Didn't get over 20mph or so and when I back off the throttle I get a rotational tapping/clunking from the u-joint end of the enclosed driveline. I reassembled painstakingly and with many pictures and notes. What in the world am I missing? It accelerates with no noises. Only on deceleration while in gear. I took it all apart and reinspected but found nothing obvious.
Anybody have some ideas?

How did you isolate the source of the noise to the U-Joint area?

It’s coming from right below the floorboard.

After a quick search I learned that there are a stack of gaskets that can be used on the bell cap. Does this bump the bell back on the shaft to create clearance perhaps for the u-joint? I used one gasket

They are not for u-joint clearance. They are shims to get the proper tension and seal for the ball housing. Some units need more than 1 shim to get the tension correct so they give you a bunch. If you are getting clunking on deceleration, try looking very closely at the u-joint assembly and the front bushing in the torque tube. When accelerating there is constant pressure on the parts, upon deceleration everything can get loose and sloppy. Look also inside the bell for any marks or scrapes where something is rubbing or hitting.

That bushing is one part I didn’t replace. It was quite snug during removal. I suppose it requires complete removal of the drive shaft to replace…?

I don't really know on a 46. It is simple on a 48, however not so simple on a 47. I have never tried on a 46. Somebody here has. Maybe Hanks Custodian? I would inspect the inside of that bell closely for marking and I would not drive this anymore than needed until this problem gets fixed. It can only get worse. It will not fix itself. The next level of issues that will come from this will not be enjoyable. I understand the bushing was tight. I have found that when I presume something, but do not verify, I can chase my tail looking for something I have just overlooked. Be methodical. Check every possible cause until you find it. Maybe it is inside the trans? Maybe a motor mount or trans mount? Things happen. Sometimes the timing is coincidental to another fix or repair. Chances are slim but not impossible. Nothing should be overlooked. Start with the easiest and most likely cause, then work your way through.

Boy I agree whole heartedly, I intend to sift through my work from front to back to try and figure this out before any runs more than my driveway. So frustrating to think that I may have to remove it all and start over. A lot of work for one person to remove and reinstall.

Boy howdy, isn't that the truth. It could always be worse, you could be dealing with termites who just love, love, love your house!

Update:
Okie bushing removed and replaced. Still experiencing a rotational tapping/rubbing upon deceleration and/or coasting with clutch pedal in.
It sounds like it’s coming from right below the floor board but I suppose with the enclosed driveline the noise can travel.
Any ideas on here before I open the rear differential cover and have a look?

Below the floor I'd suspect something in the transmission or maybe a clutch TO bearing.

I would agree however the problem didn’t arise until after I changed my rear gears to 3:55 ratio so it’s something I’ve overlooked or did not set properly I’m afraid.

I put the truck on jack stands, removed wheels and ran it in gear. Couldn’t find any noises like I was hearing when I tested it on my driveway. So I removed the differential cover and found this. How is the pinion gear rubbing on the carrier when I back off the gas? What did I miss during reassembly???

I wish I could help you. I knew enough to know I didn't know enough so I sent mine out to be done. Seems to me that there was maybe a locating pin to be driven in that held the entire shaft from moving for and aft?

Interested in this thread. I have a '46 truck and planning to swap to 3:55 gears. I was debating on trying to do it myself or taking it to a driveline shop. The shop is busy now, but told me to bring it by around Christmas time. Doing lots of reading right now.

I'll bet that the three pins with lock nuts didn't get positioned correctly. They engage a collar that holds the front pinion bearing forward. If the collar isn't fully forward on installation, the pins won't be able to keep the pinion from moving backward. The attached figure is for an AD differential, but I'd bet the '46 would be the same.

Kevin, I no longer have that differential, but in this case I think I'd loosen the lock nuts and tighten all three of those bolts. Then I'd watch to see if the play disappeared. There will be some room between the bearing and the shoulder...I would see if those beveled bolts would cause the piece to pull forward to move the pinion bearing away. If that doesn't help, then obviously something is allowing the pinion gear to travel toward the rear...where deceleration is going to cause it to want to travel anyhow.

Jon, I agree that would be my first attempt to fix. But I recall another Bolter having the same issue and needed to somehow get that collar pushed forward of the bolt holes. He may have even stood the torque tube on it's forward end to get a gravity assist. Maybe something could be inserted in the bolt holes to persuade the collar into it's proper place after pushing the pinion forward.

Kevin, I'm going to add to my suggestion. Those bolt holes just guide the beveled bolts in to where they connect with the beveled part of the front pinion bearing collar making it snug with the retaining edge. They could be loose and the twin bevels do provide a good amount of adjustment. Looking at a different set of notes, the pinion bearing retaining nut is what will limit pinion shaft rearward travel by connecting with the front pinion bearing's inner edge.

If the bearing itself isn't snug it will allow an in/out movement of the pinion shaft, but if it is tight (which will be handled by screwing in the 3 bolts) and if that bearing hasn't failed, I think the pinion bearing nut has become loose. Looking at the digital image of the damage, the pinion is moving backwards by a couple of mm. If the bearing has failed, that could happen and if it is very loose, that could happen but if that retaining nut has gotten loose it would also be a big culprit. Maybe use a piece of wood and a small hammer to tap the pinion gear in as far as it will go and then use an angled piece of metal to try to pull it out toward you. If the bearing is loose, you will see it move (the bearing will be visible through the teeth of the pinion and if it follows the movement of the pinion there's the answer). If the nut is loose or if the bearing has failed, you won't see the outer edge of the bearing move. Hope that makes sense.

The pinion retaining nut could be a possibility, but that needs to be torqued till your eyes bug out. I imagine a failed bearing would allow the same thing, but the OP said he had just installed the R&P and I assume would know if the bearing had failed, or had installed a new one. I haven't reviewed the R&P swap instructions, but I believe the front pinion bearing needs to be tight against the forward end of the differential case. I know there's a tool to set pinion depth, but not exactly sure how that adjustment is taken, or if it's associated with the tapered pins and collar.

[on edit] the pinion depth is set by shims in front of the front bearing. The tool sets pinion to bearing clearance (according to the shop manual,) but I can't see where that's really necessary unless the rear roller bearing outer race moves in relationship to the inner race, which should be against a shoulder on the pinion shaft.

The rear bearing and the front pinion bearing will move in unison because of the spacer pieces, though, yes? My experience has been so...if the front bearing moves, the rear bearing will follow. If the pinion gear is moving in/out with no associated bearing movement, it would mean the pinion nut is loose allowing just the pinion shaft to move or the front bearing is shot and it is not retaining movement as it should. You are correct...that nut has to be tightened until your eyes bug out. I've seen a couple that for one reason or another (and you can't unscramble that egg) were loose.

I’m a new member here and new truck owner contemplating this conversion. Reading numerous articles and reading the link and tech tips, This is something I think I could handle doing. On Chevys of the 40s it looks like the ring gear set is $400 and the install kit is another $424. According to the link, the benefit is only about 500 RPM at 65 mph. My question is, is that beneficial enough for the price you’re paying? Although I would like to keep the truck stock with stock wheels, it’s not out of reach for me to consider doing a complete rear end and transmission swap. Thoughts are appreciated.

Most of the people who are driving stovebolts these days aren't old enough to remember when their trucks actually worked for a living. They seem to be terrified to run them anywhere above 2000 RPM for some reason. These old engines were designed to run all day somewhere north of 3K RPM, so the obsession with high rear end gear ratios is sort of silly. P.T. Barnum had a saying about those kinds of folks! Keep the connecting rod bearing clearance down to a minimum (around .0015") and "drive it like you stole it!"
Jerry