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73-87 Chevy _ GMC Trucks => Engine/Drivetrain => Rear Drivelines, Drive Axles and Gearing => Topic started by: SUX2BU99 on June 04, 2008, 05:07:47 pm
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Can somebody give a quick rundown on which years and diff's interchange as a direct bolt-in? I have an 81 1/2 ton, 5-lug axles and 12 bolt. Looking for the same to directly bolt in. I think I read on here that 10 bolts which were put in 1/2 tons to replace the 12 bolt in 82+ have different yokes on them. That doesn't sound like direct bolt in to me.
I'd like to know what years of trucks, SUV's and vans I can scour the local papers and craigslist for. I found a 3.42 posi (which is what I want) from an 88 Suburban 4x4 but I don't know yet if it's a 12 bolt or how many lugs. I sure do find a ton of 14 bolts from 3/4 tons though.
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1973-1981 = 12bolt
1982-1991 = 10bolt.
If you want something that will bolt in, get one from a 4x2 NOT a 4X4 from any 73-81 2WD Pickup, Blazer or Suburban 1/2T.
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88 will be a ten bolt, if its 4x4 it will be 6 lug if its 1/2 ton. No other option.
10 bolts are a direct bolt in. the u joint is wider and the caps are bigger diameter. It still bolts right in with no modifications. You have to replace the u joint with a combo joint. 10 bolt size one way, 12 bolt size the other. Bolt in!
Anything from a pickup, suburban, blazer will be a direct fit. Vans do not fit.
As far as using a 4x4 10 or 12 bolt 4x4 / 6 lug, all you have to do is swap your axles, baking plates, brakes, & drums over to make it 5 lug.
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Awesome, thanks for the detailed info! I wrote the guy and he confirmed back to me that it's a 10 bolt, but the good thing it's a 5 lug. That's cool that a combo u-joint is available. So I got 2 out of 3 things with this 10 bolt: it's a 3.42, it's a Gov-loc, buuuuut it's a 10 bolt. If I had a 10 bolt right now, it wouldn't bug me so much but I got a 12 bolt and I just added more power to my truck. What's your experience been with 10 bolts and them holding up? The diff has about 85k miles on it.
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The 10 vs 12 are virtually identical in strength.
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Oh really? Didn't know that. I guess the big differences between the 10 bolt to the 12 is a little smaller ring gear diameter and a few less splines on the axle shaft? I suppose since I'm not towing anything or dumping a clutch a high RPM on slicks or using a transbrake, I'm probably pretty low risk for busting a 10 bolt eh?
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We put a wild 454 in an 81 with a TH350C and 10bolt and shot about 150HP nitrous to it. This was a weekly event as it was street raced when we were younger and was taken to the track OFTEN. The TH350C couldn't take it and lost all forward gears after about 3 months.
My brothers 2000 Silverado has the same 10bolt with 3.42 and an Eaton and it used to be at the track every weekend on ET drags hitting 1.8 60ft for over 2 years 10 months out of the year. It is Turbo'd and made 575lb/ft. The rearend is what came in it from the factory except for the Eaton. He has been through 4 trannys so far.
10bolt ring diameter is 8.5" 12bolt is 8.875"
10bolt pinion diameter is 1.625" (30 Spline), 12bolt is 1.438" (30 Spline)
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Beauty! Thanks Chris. I won't be discouraged then at all about buying this one. Dude wants $350 but it's about a 3 hr. drive from home. If I can't find something locally, I'm going to take this one.
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HOLY MOLY! $350? Is it completely rebuilt? Around here a used 10 or 12bolt generally is like $75.
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:o Say what?? Wow, no up here it seems that min. price for a diff that isn't blown up is at least $100 for an open 10 bolt with highway gears. A posi 3.xx doesn't suprise me for over $300. 14 bolts are everywhere for $100-200. This one is just pulled off a wrecked Sub with about 85k miles on it. One dude has a car 12 bolt for sale for $1500!! It's an aftermarket rear end though but still....
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Where do you live?
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for $350 I think that i would find a rear end with my gears and just order an auburn pro series and bypass the junk gov lock! 3.42 gears shouldnt be too awful hard to find! personally, Im a 12 bolt fan. 30 spline axles vs. 28 splines not to mention 8 7/8 ring gear vs. 8.5.
I did buy a 10 bolt one time however for $400 dollars (delivered to me however). Its a front axle with 3.73 and an eaton posi with new in box timken bearings and seals and brand new hub assemblies. I figured $400 delivered was quite a fair deal even though I had to but the hubs together...
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Axle spline count can be changed via the carrier buy using the 88-up limited slip. The only negative against the 10bolt then is a ring gear that is 3/8" smaller in diameter. Everything else is larger.
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I called around to some wrecking yards and found more 10 bolts; no 12 bolts. Prices varied from $400 complete, to $150, to $95 (u-pull). Nobody had ratios available. It's a see-for-yourself kinda thing. The $150 is about 7 min. from my house so I might as well check that out and pull the cover to count teeth. A Gov-lok would be nice, which is what the $350 one has, but I'm not set on one. Less to blow up lol
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Can anyone who knows give me a number for what a ring/pinion swap would cost for labor? If you don't want to publish prices, how about time in hours? Justmulling over whether it's worth it to drop about $200 on a new ring/pinion and have it put into my 12 bolt, or to buy a 10 bolt with what I want for about $350 and a new u-joint and put it in myself.
I just called probably the biggest place around here that specializes in rear ends and they quoted me $750-850 to swap the r/p with a USED one (allowed $225 for that, I can buy new for that price....), new bearings and $425 for labor. Sheez. They won't install customer-provided parts either. I remember phoning them in 1995 to fix the Trac-lok on my Mustang GT and put in a new r/p. That was around $1000 too as I recall. Ouch.
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Is that with you dropping the truck off? or you dropping the diff off? I think a buddy of mine that used to do it charged $200 minus parts with it OUT of the vehicle.
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That's with it in the truck ie. driving it to their shop and they do it on the hoist.
Any ideas on what to look for in this combo u-joint? I looked on Jegs and they just give diameter dimensions. I think I saw somewhere there are basically 3 commonly used yoke dimensions that most manufacturers used on their rear ends.
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Went out today and looked at the "10 bolt" I found at a local place for $150. Was pleasantly suprised to find out that it was actually a 12 bolt, and lo and behold, we open it up and it's a posi! Fluid looked good and no visible metal shavings that I could see. Counting the teeth would have been difficult just because of where and how the diff was sitting but the guy found the numbers stamped on the ring gear and on it was "10:34" amongst others. I'm really hoping that means 34 pinion and 10 ring teeth....
Anyway, I did buy it. I really should count it just to be sure but now I have it home (well, in the back of my truck) I can look it over really close. I feel I got a good deal since it's a 12 bolt posi and as far as I know, the ratio I was wanting. It's covered in light surface rust from sitting outside but I plan a thorough clean up, cover it in Chassis Saver and put some new brake lines on it most likely.
Things are freakin' heavy though. It's going to be fun getting it back out of the truck and then installing it.
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That sound about right. I have an in=law that works for a drivetrain company that quoted me the same price, but normally it costs around $1100-$1200. But that's with new gears, bearings seals the whole nine yards.
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To me, that's just alot of money for not a whole lot of gain. I did some net searching and found that GM did offer a 3.40 ratio, RPO HE4. So I'm pretty happy thus far that I found exactly what I wanted, for the price I wanted. Dude even said too bad for him he quoted me on the price already, now that he found out it was a posi, he would have quoted me more. Score for me!
Hopefully the brakes won't cause me any grief. I only plan on putting new hard lines on it and repainting the housing and drums.
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88 will be a ten bolt, if its 4x4 it will be 6 lug if its 1/2 ton. No other option.
10 bolts are a direct bolt in. the u joint is wider and the caps are bigger diameter. It still bolts right in with no modifications. You have to replace the u joint with a combo joint. 10 bolt size one way, 12 bolt size the other. Bolt in!
Anything from a pickup, suburban, blazer will be a direct fit. Vans do not fit.
As far as using a 4x4 10 or 12 bolt 4x4 / 6 lug, all you have to do is swap your axles, baking plates, brakes, & drums over to make it 5 lug.
I know this is an old thread but the question is similar since I might just be hunting around again for another donor diff. So if I wanted to take a 4x4 12 bolt and make it fit my 2wd I need to swap the axles and I'd swap over all the brake stuff anyway since it was all new as of July last year. Why though do the backing plates have to be transferred? Isn't that the same as the axle flange? I can't recall what held that on. Was it 4 bolts?