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Started tonight on a tear down of a 3.91 W-27 rear end. The rear has been sitting in the corner of my garage for a few months now. When I picked it up, I took the cover off to check the the gears. As expected, it was a 3.91 gear since the rear came out of very early HD cooling 1970 W-31.
Disclaimer: I’ve never disassembled a rear end so I’m confident I’ll be seeking the advice from folks on this site. I’ll try and document as much of the markings that I can find, and I’ll post several pictures along the way.
My primary objective for tonight was to just find the two letter code. Unfortunately, I couldn’t find it after sanding with 120. I’ll expand my search area and look again later in the week. I spent a good thirty minutes trying to dislodge the drum. The car had been off the road since the late ‘70’s, and stored outdoors in northeast winters, so the rust is pretty nasty. Finally, with a little help from the hammer in between the studs, the drum popped off.
Original stamp on the underside of the cover.
Not sure if this is a factory marking from a grease marker or not.
Original bolts.
Last edited by WTHIRTY1; Jun 23, 2020 at 07:23 AM.
Here are a few shots from tonight. I reviewed some pictures of W-27 rears, and I may need
to sand a little higher near the brake line for the code on this one. At least, that’s where I’m seeing SZ on other W-27’s. My TO coded rear ends have always been stamped a little lower (or occasionally upside down!).
The colored brake springs look original and crusty. The brake line appears to have been replaced at some point.
Would the group recommend brake spring pliers for removing the springs?
The rears on my other cars have had the bell drums and NOT this style of drum. No clue if these drums are original or not...need to do some homework on that.
Brake line tab broken off on the RH side.
Last edited by WTHIRTY1; Jun 23, 2020 at 11:27 AM.
I am still afraid to tackle a rear rebuild. From my research some special tools are required and proper shimming is required for correct gear engagement for noise and reliability. I would hate to do the rebuild and have it all go south due to improper setup. As of now I found a bad pinion bearing on my 67 Cutlass Wagon. I will pull the assembly and take it to someone who hopefully knows what they are doing.
I am still afraid to tackle a rear rebuild. From my research some special tools are required and proper shimming is required for correct gear engagement for noise and reliability. I would hate to do the rebuild and have it all go south due to improper setup. As of now I found a bad pinion bearing on my 67 Cutlass Wagon. I will pull the assembly and take it to someone who hopefully knows what they are doing.
I don't plan on setting up the gears. We have a local guy here that does great work. I'll be tackling the cosmetic portion of the restoration along with the brakes, etc.
I am still afraid to tackle a rear rebuild. From my research some special tools are required and proper shimming is required for correct gear engagement for noise and reliability. I would hate to do the rebuild and have it all go south due to improper setup. As of now I found a bad pinion bearing on my 67 Cutlass Wagon. I will pull the assembly and take it to someone who hopefully knows what they are doing.
BAH, I'm sure you could handle a rear axle rebuild. I did my Type-O 14 years ago with a 3.90 gear and Supercars posi and its still doing fine. It was a great project that justified the purchase of some handy tools, like a 20-ton shop press, an in-lb torque wrench, a dial indicator, a kick-*** impact wrench and some large impact sockets, which all paid for themselves in the money I saved doing it myself. The hardest part was pressing the old bearings and retainer off the axles (the trick is to partially cut them w/ a Dremmel, then crack the bearing retainer and races so they come off more easily). The trickiest part was setting the pinion depth. Instead of using the "proper" tool that sits in the carrier bearing saddles, I used some aluminum right-angle I had sitting around from another project. After lots of VERY careful measurements (averaged multiple times), I was able to calculate the pinion shim stack and hit the correct pinion depth on the first shot. It did take me 2 tries to get the proper pinion preload, so that cost me a crush sleeve. All that is left then is to shim the carrier side to side to get the correct backlash. My success has reduced my fear of tearing into the engine next (which would be new territory for me).
BAH, I'm sure you could handle a rear axle rebuild. I did my Type-O 14 years ago with a 3.90 gear and Supercars posi and its still doing fine. It was a great project that justified the purchase of some handy tools, like a 20-ton shop press, an in-lb torque wrench, a dial indicator, a kick-*** impact wrench and some large impact sockets, which all paid for themselves in the money I saved doing it myself. The hardest part was pressing the old bearings and retainer off the axles (the trick is to partially cut them w/ a Dremmel, then crack the bearing retainer and races so they come off more easily). The trickiest part was setting the pinion depth. Instead of using the "proper" tool that sits in the carrier bearing saddles, I used some aluminum right-angle I had sitting around from another project. After lots of VERY careful measurements (averaged multiple times), I was able to calculate the pinion shim stack and hit the correct pinion depth on the first shot. It did take me 2 tries to get the proper pinion preload, so that cost me a crush sleeve. All that is left then is to shim the carrier side to side to get the correct backlash. My success has reduced my fear of tearing into the engine next (which would be new territory for me).
^^^THIS. I've done the 14-bolt in my dually and it's been working fine for five years now (though in fairness that's probably one of the easiest axles to set up ever made). Most GM axles don't "require" specialized tools, they just make the job easier. More recently I've been grabbing the Kent-Moore tools for Type O axles on ebay, particularly the ones for setting pinion depth. The nice thing about using the K-M tools is that you don't have to press the pinion gear in and out many times to set pinion depth - the tools make it easy. No more setup bearings.
BAH, I'm sure you could handle a rear axle rebuild. I did my Type-O 14 years ago with a 3.90 gear and Supercars posi and its still doing fine. It was a great project that justified the purchase of some handy tools, like a 20-ton shop press, an in-lb torque wrench, a dial indicator, a kick-*** impact wrench and some large impact sockets, which all paid for themselves in the money I saved doing it myself. The hardest part was pressing the old bearings and retainer off the axles (the trick is to partially cut them w/ a Dremmel, then crack the bearing retainer and races so they come off more easily). The trickiest part was setting the pinion depth. Instead of using the "proper" tool that sits in the carrier bearing saddles, I used some aluminum right-angle I had sitting around from another project. After lots of VERY careful measurements (averaged multiple times), I was able to calculate the pinion shim stack and hit the correct pinion depth on the first shot. It did take me 2 tries to get the proper pinion preload, so that cost me a crush sleeve. All that is left then is to shim the carrier side to side to get the correct backlash. My success has reduced my fear of tearing into the engine next (which would be new territory for me).
Well that is good info, I have watched youtube and I know what to do but just don't feel comfortable unless someone was watching over my shoulder giving me prompts along the way. Right now I have no press, dial indicator, inch Lb wrench. At my age I don't think its worth the investment, I cant see myself doing this job again but I probably would have to if I attempted it! LOL Thanks! Now I can do an engine job with my eyes closed!
Last edited by Oldsmaniac; Jun 24, 2020 at 11:19 AM.
I have an assortment of these tools, different styles and brands that I've acquired over a lifetime. Basically these are all your really need:
The barrel end with a tab at the end of the pliers is, IMO, the most important tool. Makes removing and installing the springs MUCH easier.
Also, I've noticed that the retaining cup tools have changed over the years. The old ones had serrations on the inside, and the new ones are completely smooth. It's really hard to turn the cup using a smooth tool, especially when that cup is compressing a spring........ Thankfully my dad gave me his ancient drum tools a couple decades ago.
^^^THIS. More recently I've been grabbing the Kent-Moore tools for Type O axleson ebay, particularly the ones for setting pinion depth. The nice thing about using the K-M tools is that you don't have to press the pinion gear in and out many times to set pinion depth - the tools make it easy. No more setup bearings.
You, too? I've never done a diff before, but I ain't a-scarte o' nuthin'!! I've been buying the same tools over the past year and am almost ready to put it together.
Gotta have those J- and BT-Tools to make it easy. You probably got the BT-6623 I needed; I had to go aftermarket on that one, LOL!
With the Good Book and the Right Tools it should be snap!
Picked up a sweet little dolly to move the rear end around the garage. Makes life a LOT easier!
Spent an hour degreasing the aluminum housing tonight. I used a diluted Simple Green solution and a bristle brush to get off the heavy stuff. The good news is that the grease kept this thing really clean. The bad news is that there is a ton of grease caked on to this thing!
Found a few new stampings tonight. Anyone able to help me decode them? One is a black stamp, similar to the underside of the cover, that is ‘J0289.’ Then on the other side is a ‘TB 9780.’ Assuming the 289 is a date which breaks down to October 16th, 1969. This came from an 11A car so that would make sense.
I made a very nice rear end dolly out of a Harbor Freight furniture dolly fitted with some 2X12 with half circles cut to cradle the axle tubes, and 2X4s going between them. I'll take a photo and post it here. If you think you might consider tackling a differential rebuild, view the multiple part Weber University training video on youtube. I found it excellent. (seem to be having trouble loading the link here)
That dolly is pretty slick. Per my earlier post, this is the one I made from two 2 X 12's and two 2 X 4's on a Harbor Freight furniture dolly. A couple of features that worked out pretty well, the wide wood saddles in the 2 X 12's are pretty kind to the axle tubes when I rotate them (although I was using cloth there) and the nose rests on one of the 2 X 4's. So you can roll the differential 180 degrees and the nose will rest on the other 2 X 4. Not a great photo but hopefully conveys the idea.
Jimmy, I think Inline has the holders for the brake lines on the tubes. I know I had to do one a long time ago on my 69. I think I made it, and shortly after Inline or somebody was repro-ing them.
Last edited by mrolds69; Jul 20, 2020 at 09:07 AM.
MrOlds69, you are correct, Inline does have them. But Jimmy, do you need them? I see at least three in your latest picture. If you do need them, here's an idea. Don't buy them. I have a couple I bought that I won't be using. PM me your address, and you can have them for free.
Jimmy, I think Inline has the holders for the brake lines on the tubes. I know I had to do one a long time ago on my 69. I think I made it, and shortly after Inline or somebody was repro-ing them.
Originally Posted by BackInTheGame
MrOlds69, you are correct, Inline does have them. But Jimmy, do you need them? I see at least three in your latest picture. If you do need them, here's an idea. Don't buy them. I have a couple I bought that I won't be using. PM me your address, and you can have them for free.
Good spotting, gents. The tabs are all there except one is missing the portion that folds over the brake line. I'll take a look at the ones from ILT. I was considering grinding all of them off to get a clean shot at the tubes and then re-tacking them on. Appreciate the tips.
Good spotting, gents. The tabs are all there except one is missing the portion that folds over the brake line. I'll take a look at the ones from ILT. I was considering grinding all of them off to get a clean shot at the tubes and then re-tacking them on. Appreciate the tips.
I think it is a trick of the light/shade on the three that are present. Aren't the hold-down tabs still there, just lifted away from the tube? I just took another look at mine. There are only three tabs total on the axle; two on the driver's tube, one on the passenger tube.
Last edited by BackInTheGame; Jul 21, 2020 at 07:03 AM.
Reason: update info
Along similar lines, I just had my 69 Cutlass Convertible Differential rebuilt by a local Axle Shop (3.41 Posi) and have a small leak in the Cover Seal. Does anyone know the Torque Specs for the Aluminum Cover? Factory Manual shows 25 Ft/Lbs, but that is with the Steel Cover. Any guidance would be appreciated! Thank you!!
