Posi for Street Cruiser - Auburn HP/Pro or Eaton

I will be upgrading my stock 2.78 differential in my '66 Lark. It has poor traction, so it will be upgraded to a limited slip diff and the gears will be changed to 3.55 since the car has the 200-4R OD transmission

The car has never been raced, but I do like to stomp on it to get ahead of traffic on turns and exits.

The Jegs and Summit catalogs show three choices for the differential - Auburn High Performance, Auburn Pro, and one from Eaton. The advertising states that the Auburn High Perfromance is close to a stock replacement, while the Auburn Pro is more expensive and is described as "agressive". The Eaton unit is the most expensive, and sounds like it is the most durable for racing.

Which one of these three do you recommended for a street car? I don't want annoying chatter or slamming effects that may be appropriate for a race car. Appreciate your comments.

 

i have the auburn pro in my z28, and it's a street car.....i would say, as long as you get the backlash right, chatter isn't going to be an issue with any of those choices......

 

I have the Auburn in mine, brand new maybe 500 miles on it at the most and it's very streetable no problems at all. The only issue I've had is that at the track I've been blowing away the right rear and the left isn't doing anything. I have about 9 passes and the same thing happened on all but two runs. So I wondered if something was wrong? I did some street testing :3gears: and it was a different story, two long straight black stripes. So I think the problems at the track have more to do with the lack of other needed equipment back there which I'm addressing as we speak.

 

yeah, last year at the track i ran a 12.5 with a 1.8 60', this year i haven't taken it to the track, but the street traction isn't there, even with drag radials...may have something to do with the tci ssf 4200 converter i put in this spring :laugh:

on ls1tech.com the guys running 10 bolts say the eaton is by far the way to go, i haven't had any problems with my auburn pro though....

 

traction and posis

Ok the street auburn is as good as a stocker you got from the factory...pretty much. Auburn pro is suppose to have a better degree angle cut to the cone to make the mating better to give better traction and holding power.
With the eaton you have clutches (plates) some use carbon fiber (aggressive) some use steel (long lasting) and factory daisy wheel (not suggeted to use any more(design flaw) They shatter under high shock load(4200 launches...lol.) :3gears:

At the track the conditions are so sticky that a street auburn with 455 torque might have a little bit of walking(slippage) Could be from the launch being so hard that the suspension actually unloaded the weight enough from that side of the car it let the posi slip. Alot of variables to deal with ...But suspension plays a large factor at the track as far as hooking large amounts of torque.

As far as the chatter...Gear will not produce the chatter it is the cone or clutch trying to grab and get tracking. That is why the addative is used. It is an anti foaming agent so the clutches will slide smoothly in the corners... That is where you will get your chatter mostly in the tight turns -like right turns.
The CHOICE... well it always seems to come down to money. buy the best unit you can afford. Sounds like a good used unit might just do you fine if money is an issue. The only problem is finding the 3 series unit and I DO NOT have a problem with spacers. As long as they are installed correctly they will work fine for the street and mild track torque. I have personally had a 454 monte Carlo of mine doing 12.0 with a spacered rear 3 series with 4.10 gears. It is still going. 9 -10 years later. slicks and all. But I can rebuild it too. .
If you do not want to go into the rear again and are keeping the car for a good long time speend the money and get it right.
If you need an eaton 8.2 new 3 series shoot me an email I have a supply and the price is better than summit and jegs.

Good luck on the diff. Jim :TU:

 

my bad on the chatter :error: .....so does improper backlash cause a rear whine then?
**sorry for the hijack**

i also read that eatons will just break, where the auburns will wear out...i would think that would make the eaton more desirable for the track(less performance loss till it goes), and the auburn style better for the street(you'll get some warning before being stranded)......does that sound right Jim or am i not making any sense o No:
josh

 

????

Ok , I see alot of you guys are worried about breaking. If all these units are installed PROPERLY they should all work well for a very long time. Look how old the factory ones are and they are still going after 30 years.

You can have the stongest of componets on anything (engine trans rearend) BUT if the componets are put together WRONG. They won't work for crap That makes sense right?

All rears can go in many different ways...lol . Cones are bigger slabs of metal and tend not to break into pieces...lol They still have spiders gers though and that is where most of them give up. The eaton will shatter a clutch now and then but is a fairly easy fix and in expensive do it your self fix. You really must buy what you think will work best for you as far as price and how much strength is needed. Everyone wants the brute parts that do not break... BUT EVERY THING BREAKS!

I hope some of this info helps and does not confuse more.

The back lash will cause the gears to either prematurely wear out and over heat(too tight) or chunk a tooth (when too loose) If the pattern is off that will cause some whinning noise and whirling noises are usually bearings. This is a general NOT written in stone opinion. I have seen and heard many different thing happen and noises come from diffs. Make sure it is not the tranny or the road mating with the tire or even bearings in the front of the car. Noises are tricky in a car esspecially if you have load mufflers. Jim

 

Actually, cost is less of an issue than reliablilty and quiet.

Figure that my engine, even with mild mods, produces maybe 250 hp/340 ft-lbs torque by modern measurements. So, I just don't have the same durability requirements as many of you have.

Sounds like nobody is endorsing the Auburn High Performance version, leaving the Auburn Pro and the Eaton models. Would you advise paying the higher price to buy the Eaton unit for a street cruiser?

 

Hi Harry - I'm no expert, but what I've learned is that the Buick rear is sometimes hard to figure - at least when it comes to parts. I do not know what the 66 has for a rear, but don't trust the Jeg or Summit catalog. Check with an expert on what you need and what will fit. oPh and Jim are good resources. I do not know anyone in our area that is good with Buick rears. If you know someone, let me know! lol!
- Bill

 

posi

All I am saying is have it installed properly and almost anything will work well and buy what you can afford. You want to have fun with your car. It is no fun getting into a car that you have zero gas money to make go....Right? lol

Both units work good or they would not be selling them for the money they cost. I can help on eaton posis if you need them. I will beat summit and jegs for sure. I get them from eaton directly. Volume discounts... I am sure some companies can under cut me for sure but they also have alot of overhead to pay for too. Look at summit. A huge company should be able to give a better discount then they do. But they do not. ??? I do not know why. 2 big stores maybe that is why and you all will pay the price too. So why lower it?

The lockrights went down to 199.99 there for a while when the power trax were introduced and I am kicking my self for not buying a ton at the time. :ball: I still like this product for its capabilities and being able to use those unwanted open carriers.

I would think the auburn would and should work just fine for your car. Jim