$700 Eaton posi + install...Good deal?

[Matt Weiser]

A local shop today quoted me $700 for a new Eaton posi unit including installation. I was told about $350 for the unit, a $250 flat installation fee, and $100 for an axle parts kit (new bearings, seals, etc.). Is this a decent deal or am I high? Sounds like a good price on the Eaton, but what about the rest?

I told him I only wanted the stock posi rebuilt but he said the stock GM units are junk and I should put in an Eaton. I don't really want to spend for an Eaton unless it's really worth the coin.

This is a local shop that specializes in diffs and driveshafts and apparently does lots of work for the local racing community. I showed up after hours and the owner let me in anyway, showed me around his shop, nice and clean, said I could sit through the whole installation and watch how it's done. Seems like a straight-up guy.

Thoughts...?

 

[Two Lane]

Matt,

How long did your stock posi unit run before giving any probs?

Are you racing a lot? If so, an axle upgrade usually comes at the same time a posi upgrade becomes necessary.

If street use is your primary use, and you're not running major-HP with serious traction, why not just refresh your factory posi?

Food for thought...

 

[Matt Weiser]

Originally posted by Two Lane

If street use is your primary use, and you're not running major-HP with serious traction, why not just refresh your factory posi?

Food for thought...

Well, that was my thought, too, but this guy was really pushing the Eaton. My car is mainly street driven and I don't really plan on dragging it but may do some autocrosses and road course events.

The posi has 150k and came out of the same car I took my motor and tranny from. I makes a pretty loud howling noise at highway speeds and a knocking sound when I stop and start. So I figure its rebuild time.

Anybody else...?

 

[Joe 1320]

Doubtful that any straight line noises have anything to do with the posi. The howling noise is probably the pinion bearing going south. The clunking noise when you start and stop could be carrier bearings and or increased backlash due to worn bearings. The telltale sign of a posi needing a rebuild is if during wheelspin, only one tire spins or one tire spins a considerable amount more than the other. Even then, a rebuild of the posi portion cures that. IMHO, rebuild the posi, have the shop put in new pinion bearing, carrier bearings and axle bearings. You will be good to go. Replacing the posi with another unit cuts down on labor charges but it increases parts charges.

 

[Red Regal T]

GO SOMEPLACE ELSE! THE GUY JUST WANTS IN YOUR POCKETS. STOCK UNITS NO GOOD? THAT'S AN OUTRIGHT LIE.

 

[UNGN]

By my calculations, he's about $100-150 too high.

 

[c&cgn]

Someone correct me if I'm wrong but my understanding was that our factory posi was actually made by Eaton for GM?

Either way, lots of guys have gone real fast with the factory posi. I would just rebuild it and save some money. Now if you plan to race the car and hope to go mid 11's or better in the future I would recommend rebuilding the factory posi but installing aftermarket 28 spline axles at the same time.

 

[Intercooler]

Either way do it yourself! It is very easy! Rebuilding the stocker can be a little tricky but installing another Eaton isn't at all. GearsRUs has a nice install kit and price on the Eaton. You will have everything to do the job and the aftermarket Eatons are better than the factory unit. The overall construction and material thickness is greater and the pre-load springs are 400 lb. compared to the 200 lb. Z spring in the stocker. Mine chirps a little on occasion around corners. If you do track only Eaton has optional 800 lb. springs but it will be like a mini-spool car. Most just run the400 lb. spring. If you re-do the stocker clutches are available but I don't know about pre-load spring. IMO if you do it but can't get a new pre-load spring to make it like new (they lose tension after 17 yrs. ) then get a Eaton.

 

[GNVAIR]

The stock Eaton is good well into the 10's. You can get a rebuild kit for about $60 and new factory clutches for about $90.
I have a contact that can get you the parts for minimal over his cost. Email me offline if you are interested. He also has a method for adding substantially more preload to the factory Eaton by eliminating the S Spring and adding the coil style preload springs. If you have access to a press, you can probably do the whole job for under $250.

 

[Joe 1320]

Originally posted by c&cgn
Someone correct me if I'm wrong but my understanding was that our factory posi was actually made by Eaton for GM?

Yep.

you can rebuild it very easy. The only part of a rear end rebuild that is usually beyond the skills of a shadetree mechanic is axle tube straightening and backlash adjustment of a ring pinion. Physically rebuilding the posi unit is a simple bolt together.

 

[Matt Weiser]

Thanks for all the feedback everyone.

GNVAIR, thanks for the offer. I'm not against doing the work myself, but don't I need special tools and stuff to set backlash and get everything set up just right? Or would I just reinstall everything with the same shims I took out?

I've worked on just about every part of a car but diffs remain a "black art" to me and I really want it done right the first time. Maybe I'll go back to this shop and ask if he'll just rebuild my stock rear end. Doesn't really sound like I need an Eaton and I didn't want one in the first place. If he pushes on the Eaton again, I'll just go elsewhere.

IF I decide to do it myself, can anyone recommend a good book or website? I have a factory service manual, so maybe I oughta just start there.

Thanks again!

 

[Joe 1320]

IMHO,

find another shop. Never hurts to shop around.