The Stovebolt Site Forums The Shop Area Driveline 57 rear end leaks

My 47 GMC has a 57 1/2 ton Chevy truck rear end, and it leaks pretty bad. I was hoping to pull the rear cover off, clean everything, reseal it, add some RTV to the front side of the equation and hope for the best. Unfortunately when I crawled under the truck I discovered a mess of gear lube slung in all directions leading me to think it's leaking from the pinion seal as well as from the outer gasket areas. I figured It to be beyond my abilities, but decided I should look for some info here before setting the truck to the side until a large pile of money lands in my lap to have the local axle shop fix it.
I looked in the main Stovebolt site as well as some random searching on the forum for info on how these things come apart. Can someone point me in the right direction, (or send a large pile of money)?

It's really not that bad of a job. If your going to replace the rear cover gasket you can go ahaed and rain the diff and not make that big of a mess. The pinion seal is pretty straight forward, remove the driveshaft form the yoke and slide it to the side, you can zip tie it up out of your way and not have to remove it from the transmission. Remove the yoke, the pinon sheild should come with it. The seal should come out with the use of a hammer and a chisel or punch. Clean everything up and replace the seal, they have seal drivers for this or if your easy and careful you can use a soft faced hammer. Clean up your rear cover and install a new gasket, put everything back together, refill the diff and your done.

Hmmm....OK, tempting. I didn't know if the yoke came out with out removing the whole ring and pinion set up.
Thanks.

So, do I really need a gasket? Can I black RTV the diff and glue it back together (with the bolts)?

Before you do anything, clean and mark the relationship of the nut to the yoke. Use a chisel or awl and make a good and visible line across both of them. Then after you remove the nut, make a note of the relationship of the yoke so you can get it back on the same splines. Then replace your seal. Then put your yoke back on, replace the nut and tighten until the lines you made just line up and then go just a little bit tighter. Just a bit. Why? There's a crush sleeve in there. You don't have to replace it, but you do have to be careful to put it back like it was. That crush sleeve when it was installed took a LOT of torque to set.

Alternatively you can remove the crush sleeve, slide it over a piece of pipe and hit it with a hammer until it is a bit longer than it was. Then it can be re-used. It won't require anywhere as much torque to compress it as originally, and personally I'm not a fan of this procedure. But I've seen people do it and they say it worked for them.

The crush sleeve does a couple of things...pre-loads the bearings and keeps the pinion from wanting to get loose.

Well, unfortunately I didn't do any of that. Didn't read this till after. I moved the driveshaft over. Then loosened the nut. The yoke was pretty loose in there even with the nut on (meaning there was a lot of play in the yoke moving in and out). The nut came off like nothing. I popped the seal out and the spline and bearing set seems ready to fall out. Not sure I even have that crush sleeve. Can you tell anything from these pics Jon?

I guess it looks like this ?

OK, the more I'm looking at this it looks like the crush sleeve is what the bearing is set against inside. Like a bearing race.?

The crush sleeve sits between the pinion bearings (inside). To remove it you would need to remove the front pinion bearing and pull it out with needle-nosed pliers. Sorry you got things mixed up. We'll hope for the best. I've seen pinion nuts pretty loose myself. I think it comes from general wear and age. You'll probably be ok.

Thanks Jon,
It also looks like this thing had some sort of nuclear meltdown at some point in it's history. What the heck would cause that carnage and is it still there? The oil looked pretty good in the pan and there's no metal in the bottom of the diff.

The pinion slid back past where it meshes with the ring. And then nothing good happened until the driver was able to stop and change his underwear. Probably woke the dead. You can see where the pinion gear is still buggered up a little in there. Hopefully some prior owner cleaned all the mess out of there. Still...as long as it doesn't happen again you may be ok. I've seen worse. If you were going to drive this around the country...say 20 or 30,000 miles a year, I'd suggest you disassemble and take a close look, but if you're just scooting around here and there, it may not be too much to worry about.

You asked about a gasket and I failed to answer that. The basic answer is "it would be good to have one" but the truth is you can use RTV if you apply it correctly and go around all the bolt holes. I don't know where you live but those gaskets aren't really costly...I paid $4 the other day for one and have paid as little as $2. Alternatively you can lay the cover on top of a Pendaflex file, mark it and cut it carefully out of that. As long as you seal it well, you'll be ok.

Thanks again. I ordered a gasket from the local auto parts store. Won't be in till tomorrow afternoon. Leaving town in the morning and was hoping to button his project up. No biggie. My ambitions of driving my cars is always pretty high, but that never seems to materialize. I've got a couple that haven't left the garage this year. Wanted to drive this truck to my buddy's place in northern Michigan about 4 hours away. We'll see if that ever happens.

Just thinking, did the loose nut contribute to the pinion gear slipping back? Tomorrow morning I'm planning on putting the new seal in, slipping the yoke back in place, then the washer and nut. I'll check the pinion gear from the back side for movement etc.
Since I didn't mark the nut and yoke when I removed it, should I go to a certain torque setting? Should I put a drop of thread lock on it? Now I'm nervous about that happening again. This time it'll be me that needs a change of underwear.

Jon is right about the crush washer. If you have been driving it up to the point you shouldn't have any issues. Must MFR recommend only using the pinion nut once, they designed like a lock nut. Flush everything out really good and you should be fine.

Loctite...yes that is a good idea. No...just snug it up and then give it maybe a fifth or fourth a turn more...and then stop. Honestly if I had been in charge of the design, I would have used a castellated nut and a fat cotter pin. As for what caused the little problem, it is hard to unscramble that egg, but something let the gear move rearward while it was spinning. I'd put money on a loose nut and vibration. It would have sounded like a pickaxe caught in a threshing machine. Looking at the thing, you might expect the pinion shouldn't travel that far inward due to the conical shape, but that's not always the case. It is interesting to me the pinion gear wasn't changed after this but it tells me somebody didn't think it was a problem.

I forgot to mention the noise would have been the loudest during deceleration. Maybe everyone assumes that, but thought I should mention it.

I remembered a Japanese company coming out with a solid "crush" sleeve 5 or 6 ago so I went to see what I could find. Seems clear as mud to me...at least until we get down to the LSD part.


Genuine part of preload adjustment of drive pinion gear of the rear differential gear of the 86 & BRZ (rear differential drive pinion bearing spacer) by repeating the high-load conditions, such as sports driving gradually deformed to (collapse), finally backlash ( peripheral components and differential gear by tooth contact) of gear would crazy I can lead to damage of.

It is Cusco differential drive pinion color distance has been developed in order to prevent this.
Has adopted the "crush type color" is genuine parts, is the color to change to shimming type this. It is possible to prevent damage to the differential unit without parts deformed even after repeated running hard by a "shimming Type Color." This is the part that you are using for the position which is not visible from the outside, but because it is a part that has taken all of the input from the tire side and the driving force of the engine, it is very important.
It does not pose a problem if only the normal running in the normal state, but from factors such as the following, stress on this component will increase even more in sports driving. <Load factor to color increases>improved traction by wearing · LSD increase of engine power installation of the high grip tire increase of the braking force due to installation of a high-performance brake pads , such as gymkhana and circuit racing, sports driving improvement of the drive transmission response by attachments such as the clutch and strengthening etc ....

Just Mark-
I have some, very limited experience with 57, 59 and early 60's 3100 differentials. One, which is early 60's looked very much like the pic you posted from the rear,with cover removed, had limited slip (posi) which was housed within the housing that your pic shows has been knawed by the pinion.
I would suggest that you verify this before going much further.
Limited slips were first offered in 1959 and become more common in the early 60's.
If, as I suspect, you do have a limited slip, there will be a stack of 'clutchs' inside that housing.
Perhaps a po added limited slip from 59-early 60's to a 57 differential & it didn't quite fit.
Only a guesstimate from my limited experience.
delky dave in WYO

Wow, a lot to consider. Thanks for all the info! Looks like it'll be Monday before I can address it further.
The guy I bought the truck from put the open (non torque tube) rear end in it. Said it was a 57. I really don't know if that's true.

To see if you have limited slip, put the truck in neutral, chock the front wheels and jack it up so that both rear wheels are off the ground...no emergency brake. Go turn the passenger wheel clockwise and watch the driver's side wheel. If it starts turning counterclockwise, you do not have a limited slip rear. If the driver's side turns the same direction as you're turning the passenger wheel, then it is highly likely you do have limited slip in there. Also there are codes cast into the rear end (and some will be stamped in). They'll tell you. Please see here: https://www.chevytalk.org/fusionbb/showtopic.php?tid/263465/

Finally got a chance to work on it again last night. I put the new pinion seal in, put the yoke in and snugged up the nut. A little to tight at first, I couldn't rotate the pinion by hand. I backed it off a bit. It felt pretty good except the backlash (I think that's what the movement is called) between the ring and pinion gears. In other words, although turning the pinion gear feels good as far as the bearing set goes, there's some space between the gears. I can slightly rotate the pinion back and forth without it turning the ring gear. It's not much, but I don't know what the tolerance is. At some point I'd like to have my local guy put a 3:55 set in it. I also put the back cover on with a new gasket and black RTV. I did also snug up the loose front bolts on the diff. I put fresh gear lube in it this morning and took it for a ride. Drove about 5 miles. I figured that'd be enough to see if it was flinging around outside the housing like it was. Looks dry so far. We'll see how that goes. I'll keep an eye on it.

With the rear end off the ground I rotated the passenger tire clockwise, the drivers side went the opposite direction.

I read through that ID thread, cleaned off the sections on the drivers and pass sides of the casing. Nothing on the drivers side, not sure what the stamping on the pass side means. Hmmm....
I really have no idea what that rear end is.

the crush sleeve (pinion bearing spacer) needs to be replaced once it has been crushed beyond the proper rotating torque of the pinion If you want it to live. I've added a shim to the spacer before to reuse it but not on anything I would guarantee.

Just Mark,
Maybe you should start a Project Journal to help keep up with all your work and share your pictures.

BC59
Bummer

Craig, This has pretty much turned into an ongoing build log of this truck. It's gotten a surprising amount of views. Not sure how much of that is interest in the build log, and how much is clicking on threads that have a high number of views. I tend to do that myself. I see a thread that's been viewed a lot and figure there must be something there to see.

After spending some time talking with my local transmission and axle shop owner, I've pretty much decided this isn't the safest or most reliable thing at the moment, and probably needs a complete rebuild from a professional. I do get that he makes his living from telling me that, but I also trust his opinion. He did set up my corvette a couple years ago and I've been happy with that.

Now the quest begins to know exactly what I have, and gathering the parts I need to do the job.

AF code is a 3.90 standard (non-limited slip) 1/2 ton truck rear end, Mark. 3.55 will only be a 9% improvement and that isn't a lot. Now that you have it sealed, I think I'd be inclined to drive it a couple of thousand miles to see how it does. Given what you've done, the only change ought to be that it doesn't leak now. I believe I'd do that before spending big $$ to change to a 3.55 gear set. Good luck!

Thanks Jon. I'm somewhat afraid the flaws in the system might cause me a problem. I figured if I needed to replace the gear set anyway, I'd make the change. Now that I've had a chance to chill out a bit maybe I should put some miles on it. Perhaps ignorance is bliss, yeah I'll give er a whirl.

Seems like there should have been some numbers in the casting on the driver side. That link said they all had them. Mine doesn't. Ugh.

Mark, you uncovered the code I was hunting and now I know that rear was made between 1955 and 1958 and what it is.

I only say what I said because I've seen friends (and I am not guiltless) worry so much about rear ends, transmissions, etc that they nearly became afraid to drive the thing down to a gas station. I've also watched a lot of money disappear out of their pockets into the pockets of repair shops...and never get the improvement they were dreaming about. I also remember a rear end in a 1951 GMC pickup that when I finally looked inside while re-sealing the pumpkin cover was so frighteningly bad I stopped what I was doing. And I'd been driving it all over the place for almost 3 years...many 2 to 4 hour trips on the highway. A friend of mine (a machinist by profession and a good one) told me I needed to keep in mind that these aren't high precision race car rear ends spinning at 200mph back and forth through serpentine curves. This was way before the days of digital pictures, but I described what I found and he said his prescription was to get the thickest rear end gear oil I could find, mix about 10 or 15% of any additive with a high % of zinc d. in it (like STP) and then keep driving until it quit. Then rebuild it. Good luck!

You're seeing the aftermath of a pinion bearing failure, or at least the pinion nut coming loose and falling off. The first time the driver backs off the throttle after losing the pinion nut, the pinion gear gets sucked back into the differential carrier. The noise it makes when that happens is horrendous! It looks like somebody probably cleaned out the shavings, put a new pinion nut on, and drove on. The fact that the pinion nut is loose again probably means you've got one of the pinion bearings failing slowly and letting the nut get loose. I'd recommend a complete teardown of the rear end and replacement of anything that's worn, or swapping the entire center section for one in better shape.
Jerry

Going to Hershey next month. I hadn't thought to look for that, now it's on my list! Thanks.
Was at a cruise night last night (without my truck) and got talking with a good friend. He mentioned that a friend of a friend works for DTS . My plan at this point is to trailer it there....when the large pile of money appears.


Thanks Fellas!