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View Full Version : which 8.5 posi



joeljet
05-15-2006, 08:58 AM
getting ready to rip the rear end out of the car and am wondering which posi to use. gm 8.5 10 bolt 73 firebird 450tq/hp 99%street driven. wanted mostly quiet, smooth operation, both wheels turning, no clunking etc. eaton,auburn,? 28 or 30 spline axles will depend on what kind of shape mine are in, if they need replacing i will probably step up to 30 spline thanx joel

chicane67
05-15-2006, 09:36 AM
An Eaton. Strongest, easiest to use, easiest to rebuild and tuneable.

Dont even look at the Auburn. Once it wears, its a throw away unit. At least with the Eaton, you can tune and re-build it for under a hundred bucks. Although it may be a while until you'll need a rebuild..... I still have the same 38 year old clutch pack in mine.

diffdude
05-15-2006, 04:18 PM
The new eatons use carbon fiber clutch's. They dont last as long as the old steel ones did. Just about every one we put in the customer calls back in about 1000 miles complaining they only spin one tire. If I was going to buy an new eaton i would take the carbon fiber out and replace them with the old steel ones.

chicane67
05-15-2006, 06:14 PM
That problem has been addressed by Eaton and it is no longer an issue.

Yes, the early Eaton re-pop's did have a little to be be desired in the 'ole clutch pack department..... but that issue is a thing of the past. The newer fiber clutches composition have rectified that early problem.

If it were a real issue, Tom's differential in Paramount still sells the solid 18 clutch kit for around $85-95 a set.

chicane67
05-15-2006, 06:15 PM
Nice double post ........

diffdude
05-16-2006, 08:55 AM
Thats funny we install about 10 a week and they still have that problem. I dont know where you are getting your info from but they are wrong.

chicane67
05-16-2006, 06:56 PM
Yup, that is funny. I have been a master WD for Eaton for over ten years and have probably averaged 10+ sales a day.... not to mention the thousand+ installs.

Maybe its an issue with what you get, but Im looking at around 75-80% less in returns.

We addressed this with Eaton back around '97. I have found that it is mostly related to the HD unit. I dont recommend the HD unit, as I feel it has too much preload and creates too much heat and it does chatter, even thought the end user dosnt hear it. I also attribute this to the type of oil and friciton modifier being used. What we have found to solve this problem is to use a parrifin based lubericant....... and since friction modifier, not the synthetic type like RedLine, is parrifin based..... it homogenizes much better and negates the chatter and inhearent heat build up in the clutches. not to mention actually tuning the unit. But most shops dont have a considerable clue on what that is about. Having been brought up in this business building them for Guldstrand, which has 40+ years building these differentials for road race chassis.... gives me the clue. And tuning has a lot to do with it. A Barney bolt on shop probably doesnt have that 40+ year resource.

I will not recommend the HD unit. If the chassis is putting down 400+hp and torque.... I still put the solid steel clutch pack into it with the HD spring plates but use the 400# springs. For a driver or a chassis that sees no real track time, and HD unit will live if the right oil and fric mod is used.

Since we have been in Eatons pocket doing failure analysis for quite some time, I have had different clutch compositions to play with over the years. What I have seen in the past five years is much better than what the original clutch was.

slowcamaro
05-16-2006, 07:18 PM
I dont know if torsen makes a unit for the 8.5" 10-bolt but they do for the 7.5" and its supposed to be great. Very suceesful among the AutoX and road course guys.

http://www.torsen.com/products/T-2R.htm

diffdude
05-17-2006, 12:21 PM
chicane67,
I'm not going to get into a war with you over who sells more product or installs more. Because of your numbers I win. People like you are the reason guys like me never post. You turn it into a bias pissing match.
Good Day Sir.

chicane67
05-17-2006, 10:44 PM
Uhm.

Yeah.

This isnt a pissing match.

You made a statement, that doesnt carry its weight that denies the manufacturer of the product in question, weight in their efforts.

Its not my fault you take this.... the way you do. I wasnt making a point to be a d*ck.... but because your numbers and your comments, you are.

And who is it you work for again ??

Its people like yourself, that may not have the knowledge..... that get their feelings hurt because someone else has "an opinion", backed up with the knowledge and experience with the product in question. Maybe.... and just maybe...... it is considerably more than what you retain ??

Frankly, you have turned this into a pissing match with yourself.
Good day to you as well. Until then.....

r1maniac
05-18-2006, 09:27 AM
I would have to agree with diffdude on this one. I've been doing diffs for a few years also and i have yet to see eaton fix the clutch issue. We are also "wd" with eaton and sell probibly around 20 a day through the shop and mail order but we try to push the auburns. You cant rebuild them but the dont have the clutch issue that the eaton has. I have always used auburns in my personal car and have never had any issues.

chicane67
05-23-2006, 08:04 PM
What a bummer for you guys.....


If it were a real issue, Tom's differential in Paramount still sells the solid 18 clutch kit for around $85-95 a set.

68Formula
05-25-2006, 04:50 AM
chicane67,
I'm not going to get into a war with you over who sells more product or installs more. Because of your numbers I win. People like you are the reason guys like me never post. You turn it into a bias pissing match.
Good Day Sir.

diffdude, I don't know where you got burned before, but your sensative meter was set to high. I read through chincane's post three times. You stated whereever he recieved his data from was wrong. He response was simply to let everyone know his experience level and that the data was not second hand. Relax, it's all good here.:grouphug:

diffdude
05-25-2006, 10:41 AM
If it were a real issue, Tom's differential in Paramount still sells the solid 18 clutch kit for around $85-95 a set.

Just so you know you can get those steel clutches direct from eaton part #ed-29403-00s so you can cut out your middle man.

chicane67
05-25-2006, 06:20 PM
But if your middle man purchases the product in quanity.... and passes that on to the end user.... why not ?? Considering that the Eaton direct price is more....

And FWIW, the part number is EDS-29403. The '00S' is the reference suffix for the "Preload system service kits" which do not include the clutch pack.

diffdude
05-26-2006, 10:01 AM
chicane67,
I was giving you the number I didnt know if you had it because you keep refering "Toms" but I thought you were WD.

I got the number off the box of cluthes and it had the 0ss on it and its just the clutchs in it.

Are you seeing the failure problems with the new cast spiders we see?

chicane67
05-26-2006, 10:23 AM
Hi. My name is Tom. My WD status goes wherever I do..... (which is true)

Really though, Tom's get a better deal because of his WD status is, in my opinion.... the best there is. Its not just a master WD.... its deep in the pockets type WD. He gets the better deal and can beat my prices on quite a few things..... so wouldnt I refer the better deal to everyone ?? I should and I do. We all use each other to benifit... its a small circle.

Ahhh, the spiders. Yup. That is what you get when you throw stock parts and high horsepower and torque.

In high HP/TQ applications, the spiders are junk..... and that is why I only use specially heat treated sets..... tumble polish the bare carrier..... throw out the pre-load pack once the unit is correctly tuned..... and stay away from 33 spline units because the carrier bearing journal get too thin.

Jim68nC
05-29-2006, 05:33 PM
well, well diff gods, umm thanks for clearing this question up for us.

I too have a 8.5 which I am in need of a posi unit to hold up well in a 68 Camaro. Hoping to get around 500ft lbs at the crank and mostly street tires. I want an install and forget it rock solid unit until the housing rusts away around it. errr ok, ok, well you know what I mean.

So, I thought that meant Eaton or Auburn. Now what - neither? Mind you, I also thought I could set one up myself to do this for the first time and hopefully only time.

chicane67
05-29-2006, 05:54 PM
If you are looking at that kinda power, I would call Tom's and have one set up for your application...... steel plates, no preload pack etc etc.

There is an option list found in the 12bolt section under "BOE" units..... Here (http://www.tomsdifferentials.com/cat3.htm)