Weakest link in '81 rear?
Thread Starter
Instructor
Joined: Feb 2007
Posts: 138
Likes: 2
From: Buies Creek NC
Weakest link in '81 rear?
What is the weakest (or simply weak) link in the rearend setup of an '81 Vette? I'm redoing the one in mine now for a 383/twin-turbo street project. I've been through the diff with all new bearings, 3.08 gear, solid 1330 U-joints in the stock 3" half-shafts...etc. What else can be done with stock stuff to get it to hold up? What usually breaks first? Second? Thanks.
Safety Car
Joined: Nov 2008
Posts: 3,720
Likes: 557
From: Seattle Washington
The 1330 U Joints go 1st. The Posi Clutchs rub on the Carrier and dump metal into the oil and do in the Bearings next. The 1980 4 speed and all 1982's used 1350 U-joints wich hold up better. Yokes, 1/2 shafts and Axel Flanges are needed to install them.
Drifting
Joined: Aug 2004
Posts: 1,883
Likes: 124
From: Lubbock TX
Most of the high power guys that are running the iron diffs install one billet cap, I'd think the aluminum one would benefit from one as well. I decided not to spend the coin on a weak diff, I'm upgrading to iron along with bigger halfshafts, U-joints, etc.
Burning Brakes
Joined: May 2008
Posts: 1,116
Likes: 5
From: Middleburg Florida
Burning Brakes
Joined: May 2008
Posts: 1,116
Likes: 5
From: Middleburg Florida
Thanks! Others have done this and it's as close to a "bolt in" mod you'll find. The iron unit bolts directly to the batwing, though you won't use two bolt holes. No big deal, no leaks and no weakness either. You will have to buy early (pre 1980) half shafts, axle flanges, strut rods and mount, and a pinion mounting bracket for the earlier cars too. The half shafts and flanges bolt right in, as do the strut rods. I did have to modify the pinion mount, I had to cut about 3/4" off the front (so it would clear the frame), and had to drill a new hole for the bolt in line with the pinion bushing mount on the frame. I also had to trim the strut rod mount for my exhaust pipes. This might also be a good time to do anything to the trailing arms that needs done. I did my bushings, and added a rear sway bar.
I got all my parts from Van Steel, if you call them, they can put all the parts together for you, they've seen this done many times.
I got all my parts from Van Steel, if you call them, they can put all the parts together for you, they've seen this done many times.
Le Mans Master
Joined: Apr 2007
Posts: 7,353
Likes: 72
From: Graceland in a Not Correctly Restored Stingray
I went with an iron differential. It's not that hard to do, and it not only improves the strength of the rear end, it improves the handling too. You have to use the struts from the earlier differentials, and that puts the struts parallel to the half shafts, improving the suspension geometry.
Safety Car
Joined: Oct 2006
Posts: 3,930
Likes: 15
From: Calgary Alberta
There is only one person I would trust machining and installing a steel cap in an aluminum diff, and he is right here on the forum. He's been doing it for a while now, and he has all the jigs set up. Check out this monster...
If you wanna keep your diff together, I would go this route. Just some advice.
If you wanna keep your diff together, I would go this route. Just some advice.
Last edited by stinger12; Feb 3, 2011 at 02:32 AM.
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Burning Brakes
Joined: May 2008
Posts: 1,116
Likes: 5
From: Middleburg Florida
Your right, not gospel, but as I understand it (I could be wrong, hell, it's not even 10am and that's already happened today!!) the new (new-old!) struts and their geometry when compared to the stock set up improves the rear stability of the suspension in general. Is this not true?
Le Mans Master
Joined: Apr 2007
Posts: 7,353
Likes: 72
From: Graceland in a Not Correctly Restored Stingray
Your right, not gospel, but as I understand it (I could be wrong, hell, it's not even 10am and that's already happened today!!) the new (new-old!) struts and their geometry when compared to the stock set up improves the rear stability of the suspension in general. Is this not true?
Thread Starter
Instructor
Joined: Feb 2007
Posts: 138
Likes: 2
From: Buies Creek NC
Oh I like the discussion. I have heard first hand that the aluminum center is not the weakest link. I've seen many convert 80-82s to an iron center and leave the other parts stock. Why? There are high HP cars out there using a stock aluminum center but with beefed up components (half shafts, outer axles, u-joints, etc). I converted my '81 over to Brute u-joints, drilled all the flanges/yokes to accept 5/16" U-bolts, and installed shaft loops. Other than replacing parts, that's about all I can do right?
Drifting
Joined: Apr 2006
Posts: 1,911
Likes: 2
From: gold coast queensland
i been flogging a stock (apart from 355 gears ) 81 dana44 rear now for about 3 years with 420hp and 295 rear tyres. i admit i dont spend any time on a sticky track but i give it heaps on the street and so far...so good.
Burning Brakes
Joined: May 2008
Posts: 1,116
Likes: 5
From: Middleburg Florida
Oh I like the discussion. I have heard first hand that the aluminum center is not the weakest link. I've seen many convert 80-82s to an iron center and leave the other parts stock. Why? There are high HP cars out there using a stock aluminum center but with beefed up components (half shafts, outer axles, u-joints, etc). I converted my '81 over to Brute u-joints, drilled all the flanges/yokes to accept 5/16" U-bolts, and installed shaft loops. Other than replacing parts, that's about all I can do right?
Safety Car
Joined: Nov 2008
Posts: 3,720
Likes: 557
From: Seattle Washington
Oh I like the discussion. I have heard first hand that the aluminum center is not the weakest link. I've seen many convert 80-82s to an iron center and leave the other parts stock. Why? There are high HP cars out there using a stock aluminum center but with beefed up components (half shafts, outer axles, u-joints, etc). I converted my '81 over to Brute u-joints, drilled all the flanges/yokes to accept 5/16" U-bolts, and installed shaft loops. Other than replacing parts, that's about all I can do right?
Racer
Joined: Mar 2006
Posts: 264
Likes: 1
From: west central INDIANA
There is a guy on here, with an Red 82, 3.70 gear, 383 stroker with some juice, 3500 stall, and I think 700 r4 trans. He runs 11.90s and can pull the front wheels. He needs to chime in. I think his diff is stock, but rebuilt. This is from memory only. I had to take note of it, because he changed my view, of the dana 44s that are " so weak "
I found the thread
Try searching for forum member = Clint`s C3 ( My First Wheelie ( that I know of ) is the thread title ) check it out
I found the thread
Try searching for forum member = Clint`s C3 ( My First Wheelie ( that I know of ) is the thread title ) check it out
Last edited by 1980 blue L48; Feb 6, 2011 at 12:47 PM.
Burning Brakes
Joined: Jun 2004
Posts: 1,012
Likes: 5
From: Granbury, TX
There is a guy on here, with an Red 82, 3.70 gear, 383 stroker with some juice, 3500 stall, and I think 700 r4 trans. He runs 11.90s and can pull the front wheels. He needs to chime in. I think his diff is stock, but rebuilt. This is from memory only. I had to take note of it, because he changed my view, of the dana 44s that are " so weak "
I found the thread
Try searching for forum member = Clint`s C3 ( My First Wheelie ( that I know of ) is the thread title ) check it out
I found the thread
Try searching for forum member = Clint`s C3 ( My First Wheelie ( that I know of ) is the thread title ) check it out
Mike Dyer just machined and installed a steel bearing cap (it looks like the picture posted by Stinger 12) and rebuilt the diff and training arm assembly. A beautiful job and darn site less expensive than an iron diff conversion. We start racing again in about 3 weeks and I'll keep eveyone posted.
Burning Brakes
Joined: May 2008
Posts: 1,116
Likes: 5
From: Middleburg Florida
Nice launch Clint!! What are you running for power in that?? BTW, I'm sure having Mike do your rear was less expensive than the iron conversion. Off the top of my head, I'd guess mine was around $1100 including the rebuilt diff.
Drifting
Joined: Jul 2002
Posts: 1,995
Likes: 110
From: Garland Texas