Just pulling the 3rd member out of my 67SS 396ci, TH400. Has apx. 85,000 miles on it. The diff currently sports a 3:08 and single track axel. I am considering purchasing 3:55 gears and limited slip posi. My question is which brand is the best ? I have heard from an employee at a local speed shop that Richmond Gears tend to whine. He also said he has seen alot of Auburn posi's break, and recommends Eaton. Another fella said Eaton posi's are prone to chattering in the corners. Now, I am totally confused. Maybe I should just replace bearings and seals on the peg-leg I have and not re-invent the wheel. What in terms of driveability will I gain or lose ? What are popular brands of ring/pinion and posi's that don't have hidden quirks ? Thanks in advance for your help. Slo.

Unless you are driving a lot on slippery roads or pulling a trailer or stop light racing, posi is something you don't need for normal driving. You won't gain or lose any performance with it or without it. It just adds to the traction capabilities of the car.

Eaton units are in just about every GM vehicle on the road that has posi and for the most part are worry free. Yes they can cause a chatter when cornering a slow speeds but thats a normal condition. Use a 100%synthetic gear lube and this will be reduced greatly if not eliminated completely. I have had posi on my trucks for the last 25 yrs and can never remember noticing a lot of chatter not have I had a problems ever.

No quirks? Don't get a Moroso Posi then. I have one in my car. As much as I like it, it does make lots of noise and doesn't like coasting thru turns. As far as traction goes, I love it.

Hey Slo, I've had great luck so far with my Auburn 4 pro-series carrier. It's whisper quiet (I had a pro set it up) and works perfectly. I think though that Auburns' are not rebuildable, at least that is what I've been told. Hopefully it will outlast my car!

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1970 Malibu - 383 'Fog Fed' Stroker. Houston, Texas...Gold Member #39
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Elcamino, the man said a 67 SS396, he needs a posi for everyday driving. An SS would've come with 3.31/3.55/3.73 or 4.11 posi.

3.55 is an excellent choice. And I had a GM rebuilt 12 bolt that chattered in the corners. No design is immune. No big deal. Sounds like either Eaton or Auburn have good results.

Heard that GM gears are definitely quieter from a number of people. That may make a difference to you.

are you trying to say that you have a ford 9 in your chevelle? if that isnt antichrist then I dont know what is http://www.chevelles.com/forum/smile.gif

anyhow I have richmond gears in my 12 bolt and I havent heard them whine (over the gear drive, and flowmasters) http://www.chevelles.com/forum/smile.gif but yeah thats a rumour ive heard too... personally it wouldnt bother me enough not to buy probably the best gearset out there.. however my second choice (this is pure word of mouth here) would be precision gear for daily driving... ive heard that they dont whine.. as for the posi unit, I would probably go for the Eaton, afaik the auburns are a throw-em-away-when-they-wear-out unit...

good luck and let us know what you do..

one last thing is that if you are going to pay for the labor/parts for a gearset swap, then by all means upgrade to a posi..

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Mike Reeh
Gold #34
San Diego, CA

My '65 EC came with a 3.08 12 bolt with an Eaton posi unit. Only trouble I've ever had was at about 95,000 miles it started grabbing. The clutches would release with a bang during a left or right turn at a stoplight. After draining and refilling with fresh gear oil, problem went away. GM posi additive would accomplish the same thing.

When I was stationed in Alaska I just put studded radials on it during winter and a couple of sand bags in the back and never got stuck for lack of rear wheel traction. You probably don't need posi in SOCAL unless you're a drag racer.

My $0.02