Hey all, Long time reader, first time poster. I was replacing my axle seals in my 1959 Chevy apache 3100 because I noticed the p***enger rear was leaking pretty bad when I was redoing the brakes. My truck is all stock except for the engine and trans along with a 5" drop in the rear and a 3" drop in the front. When I had my rear diff cover off and was inspecting the innards I noticed one tooth on the ring gear was half missing. Half missing as in, half had broken off at some point. This was the first time I had ever had this diff cover off. I tried fishing around in the bottom of the housing with my magnet to see if I could find that pesky piece of ring gear with no success. I have driven the truck quite a bit and to be quite honest, there have been some clutch dumps and power shifts in the time that I've owned it. I have never noticed anything in its driveability even with this broken piece of ring gear, nor do I notice anything now(because I put it all back together and have been driving it since). I haven't been able to find a whole lot of info on these rear ends. Just the usual "corporate gm rear", "HO33", "55P/T" yadda yadda with not a whole lot of info on any of it but I definitely plan on replacing the broken bits. It's a 3.90 geared rear and my diff cover has 10 bolts, the ring gear has 12 bolts and I've seen some stuff on the interwebs saying that gm 10 and 12 bolts really mean ring gear bolts and then some saying that it means 10 or 12 diff cover bolts. I was thinking of maybe swapping in a 8.5" 10 bolt or a 12 bolt but people want a dang arm and a leg for those around this area. I ended up stumbling across a product from cl***icparts.com that is 3.38 ring and pinion and an exact replacement for my rear end, 12 bolt ring gear for a stock 55-64 Chevy 1/2 ton truck rear and that the ring gear diameter is apparently 9.375". Is that correct? If that's the case, that's a bigger ring gear diameter than a GM 10 bolt, 12 bolt and the Ford 9"(obviously) so I would ***ume these stock rear ends are beefier and would be more sought after than what I've read about. I would like a higher gear because at 50 mph my truck sounds like it's screaming and I'd like to get the RPMs down a little. I found a rpm calculator and supposedly my truck was right around 2675 RPMs at 50 but it seemed more like 3500 Can anyone shed some light on the rear gear subject and correct me on my ignorance? If there is another thread that dives deep into this I apologize but I haven't been able to find it. And I'm sorry for the novel. Thanks, -Drew
GMC rears were mostly leaf spring while Chevy had the trailing arms starting in the 60s. I’ve got a Dana 44 out of one. That rear probably has a lot of miles left in that condition. Unless it’s roaring. One solution could be an OD trans. Especially if you have a 3 speed. A 3 speed OD is a bolt in. Usually not very expensive. If it’s a good one. With working solenoid. Anywho, a 6 lug rear swap with a newer one would probably be cheaper than messing with the old corporate one
I don't hear any rear end noise when driving it. I recently swapped a turbo 350 in for the Saginaw 3 spd I had in it. When I originally got the truck it had the Muncie 319 3spd on the tree with the overdrive unit out the back. Unfortunately when I tore that trans apart to rebuild it I found the entire planetary gear in the overdrive was in about a thousand pieces.
Reason more giant rears seem to be less sought after than say a 9" or 12 bolt is stuff like weight and parasitic drag. Yeah one one hold up but wouldn't perform as well as the more popular rears with same gears
Yeah that's the exact one I was looking at on cl***ic parts.com. I'm thinking that might be my best bet although a newer rear end has a lot of aftermarket parts and what not. I was just baffled by the 9.375" ring gear diameter.
That makes total sense I honestly never thought of it that way. Here I thought people wanted larger ring gears for beefiness but didn't take into account the drawbacks the older, larger rears would have. Not to mention the engineers of the time made technological advances with the more modern rears to fix said drawbacks.
I have 3.38s in my 55 1st series, runs great. Those rears only had 3 ratios that I know of. 4.11, 3.90, and 3.38. Same bearings as a 55-64 car but with beefier bearing caps. Early 12 bolt side gears fit right in if you want 30 spline axles. Tom's Differentials have axles for that. Home - Toms Differentials
If I couldn’t find the chip, I’d not worry about it. If you can’t set up a Ring/pinion, take the 400 you’d spend on parts parts for the 3.36? put it towards a T5 swap. My feeble thoughts..
The easiest would have been another 3spd o/d trans (later Saginaw would be the best), but now with the TH350 a rear swap is it. Get something the right width and lug pattern and make it fit. I have a old 261, 3 speed o/d and stock H033 in my '56 panel. https://www.jalopyjournal.com/forum...1956-chevy-panel-truck.1099578/#post-12510102 I did find through mine you need to look up axle seals for a H033 to get the right seals.
The 3.38 gears would be great with the Turbo 350 or any 1 to 1 output transmission. Thing is along with 350/400 for the ring and pinion Then you have another 270 or more tied up in the installation kit with new bearings and crush sleeve and seal. If you are wanting to stay six lug the options for a rear that fits right are fairly slim with one from a Chevy Colorado being the closest in width and hopefully highway friendly gears. Even then there are three widths from too narrow, pretty close and too wide. I'm going to just let you read this and decide if that might be an option but the one that is 60-3/4 would be pretty close to right. Some have a 3.42 gear that isn't too bad all around. COLORADO REAR END (swap) INFORMATION (pics added 1/3/16) | Cl***ic Parts Talk
Man that's one sweet panel! I recently saw one on FB marketplace advertised as an original NAPCO panel but it was all beat to hell, needed everything, and the guy wanted something like $18,000 for it. I'm about an hour and half north of Fresno where Turners Auto Wreckers is. I might take a drive down there and scope out what they have for rears, maybe find a 12 bolt from a late 60's c10. Maybe while I'm there I can snag another Muncie 319 overdrive unit and fix mine. Options are there and I appreciate your input and your awesome panel.
I actually have an installation kit laying around in my parts pile I believe from USA Standard Gear. I just used the pinion seal out of it the same time I replaced my axle seals. I read some reviews on that same kit that I have and it seems some people were given the p***enger car crush sleeve and not the truck one, therefore their kit wouldn't work. Not sure how different the crush sleeves between the P and T would be. I got lazy that day and didnt replace the 3rd member-to-housing gasket and a couple hours after I got home from about a 22 mile trip I noticed an oil drip on the ground right under the rear. Got underneath and looked and sure-as-sheep it needs to be resealed. Recently stumbled across an 08' Chevy trailblazer on FB marketplace, just the ch***is, and dude wanted $500. It had a 6 lug 10 bolt. Most ads selling a 10 or 12 bolt start at around $600 and only go up in price. I guess it's time to go to pick n' pull and browse the inventory.
Appreciate it. I'll look into the T5's. I still have my bell housing, clutch, pressure plate, flywheel, etc.. from the previous standard transmissions I had in it.
Thank for link! I've never stumbled across this company. Looks like he sells the same 3.38 ring and pinion that I was looking at from cl***icparts.com for $150 cheaper! There's a big swap meet coming up in late January here in Turlock. If I don't find anything to my liking for the right price there, or locally, then I think I'll be doing business with Tom's Differentials.
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