I have a 91 RS, Lo3 305 TBI, open rear end with unknown gear ratios but I suspect 2.73.

I'm assuming I have 28 spline axles but I've been doing some reading and searching here and there seems to be a lot of confusion about this. Some say that between 89-92 only the posi rear ends got the 28 spline axles? Others say 89 is hit or miss depending on drivetrain options or what part of the year it was produced, but all 90-92 is 28 spline? Which is correct?

Anyway, What all do I need to do this conversion? I'm planning on getting a 28spline 3 series carrier, and 3.73 gears, but what else do I need as far as crush washers and shims and gaskets etc? I will be having a mechanic do the work but I need to get all the right parts.

Thanks

 

Deluxe Gear install kit, comes with everything you need,
Scroll down to Ratech Gear Install Kits,
http://thunderracing.com/catalog/?ac...&vid=6&pcid=67

 

$122? ehhh..., do I really need the deluxe kit? That's more than I was looking to spend on the carrier and ring gears. Can I get by on the basic or complete kit? What do I need at a bare minimum? New wheel bearings and seals would be nice, but that's going to drive up the cost of the labor too...

 

Complete kit.
you will want all new bearings and races.
If you go to a local parts store just for the carrier bearings and races, it will cost around $30 for those 4 parts.

 

listen to Zepher... hes right.

you'll need the full kit... if you try to piece it together by buying an incomplete kit and the other parts separate, you'll pay even more.

 

gotcha... so complete kit it is. If I'm going to do the wheel bearings and seals I would probably do all 4 wheels at the same time a later date... does that seem right?

If I were to order everything from thunder racing it would be.....?

69-G875373 Motive Performance Gears, 3.73 Gear Ratio, 3 series carrier, GM 7.5" 10 bolt rear end $189.95

85-308TK Ratech Complete Gear Install Kit, GM 7.5" 10 Bolt $94.99

total = $284.94

What do you guys think about the 3.73 gears with my LO3? I know some L98 Z-28's came with 3.73 during 91, but they might rev higher or make more power at higher rev...?

 

another thing, that site lists it as 7.5" rears 82-92... but it doesn't say anything about spline count, which i thought was different 82-88 and 89-92? Isn't spline count important? How do I know wether they are sending me a 26 or 28 spline carrier?

Also, are there 2 different kinds of posi? clutch types and gear types? or are they the same thing? Which is better and which is thunder racing selling? I was going to get a used unit but I might just go new...?

 

You can purchase small to large install kits from other sources, ie. Summit or Jegs as well as shops that specialize in gear and carrier installation to parts. If you've never done this before, I suggest that you consult with shops that sell the parts and install them as well. The advice is free and they'll assist you in the proper selections based on your needs.

Give these guy's a call; http://www.ring-pinion.com

Good luck

 

At thunder racing, the only LSD they list is the Eaton and they have both the 26 and 28 spline units. 26 spline for $469 and $537 for the 28 spline.

clutch type wears out over time, gear style is designed to last the life of the car and perform like new the entire time.
Eaton and Auburn are clutch style.
Zexel Torsen is gear style.
Not sure about the other brands on the market since the above 3 units are the only ones I have used.

 

I see where I screwed up... I thought the $189 was for the carrier and gears hahahahha, that's why I figured I might be able to go new... nope, that's just for the gears! I'm definitely gonna have to go with a used posi from ebay or a junkyard somewhere... maybe i'll just get whatever other parts I need at Napa or somewhere like that. Thanks guys.

oh, and still not sure if I want to go 3.73 or 3.42 or what... Will 3.73 kill me on the highway?

 

well the more I read the more I learn... I am going to go with the deluxe kit and have the wheel bearings and seals replaced at the same time.

You're syaing there are gear type posi and clutch type posi... you don't mean gear type as in the gov-loc do you? I've been reading that I should stay away from gov-loc... Are there 2 different types of limited slip posi's? clutch and gear?

 

Well, there are LSD's and there are Lockers. Lockers are more for dedicated drag racers, while LSD's are general purpose.
LSD's come in clutch and gear styles.
Not sure about the Lockers.

About the gears, 3.73's are very fun, you can come off the line from a stoplight really quick (if you don't spin) but you will lose some mpg on the highway if you cruise faster then 60mph.
I loved the 3.73's when my car was an Auto and mpg wasn't really an issue for me since the car gets crappy milage compared to todays cars.

When I went with the 5 speed, I swapped the 3.73 rear for a built Eaton 4.10 rear and that made the car a lot of fun to drive on the street (2nd through 5th pulled really hard), but horrible on the highway since I would be taching about 3K at 65-70mph and had a top speed of about 120mph.
After I broke that rear, I put in one from an 01 SS with 3.42's and milage improved but I lost a lot of acceleration.

 

How did you break your eaton rear? I think the gear type posi's are gonna be really hard to come by. If I can get a brand new (0 miles) clutch style posi for $125, no gears, is it worth it? or should I hold out for the gear type?

Also, I jacked the camaro up, and turned one wheel, the other one turned backwards. They turned very easy. While I had it up and running in gear, both wheels were turning forward, but I was able to stop one wheel. I did the same thing on my truck, 91 gmc sierra, and when I tried to turn them by hand, the left one I had to force and barely managed to turn maybe 1/16th of a wheel revolution before it hit something and stopped. The right one wouldn't budge at all. when I ran it up in the air, only the left wheel turned, and I couldn't stop it by pressing another tire against it to simulate traction, which should have made the other one turn if it was open rear, right? So I'm thinking my truck might have some sort of posi or locker, but it's fudged up somehow? or is that how a posi...or locker... is supposed to act when it's up in the air? Driving though, the truck does not act like it has a posi or locker. When i'm at a stop and try to turn right and pull out onto a main road, it will spin the left tire for days and days. When it's cold or rainy it's a struggle to keep it from spinning. I have to get of and on the gas 2 or 3 times before i'm going fast enough to where it won't spin

 

instead of buying a posi and gears, and opening up my differential etc.... would it be better to just cal around to junk yards looking for 90-97 camaros and firebirds, and if they have any get the vin number, then call GM and find out wht the ratios etc. are, and if it's what I want, go get the ENTIRE rear end? meaning differential, axle housing, axles hubs brakes and everything? Then it would just be hooking up the drive shaft right, no setting the backlash etc.... Would that be easier/cheaper?

 

if its a 4x4 limited slip is very common. im not at all an expert in any thing to do with the drive train i just know that it is a common thing and from watching all those spike tv sunday shows ive learned that it has something to do with locking the rear together but i dont think its quite posi. it might be more like a hybrid between but someone else will probly be more help than me.
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thats a good idea but you can probly get the specs on the rear directly form the vin number or see if someone on the site has a source because i know a few guys have sources for the info on what cars had what. for example if you go to the vert section and ask if any vin is a true vert you'll get the answers from a moderator with all of the numbers on which vin numbers had what potions. i dont know if its only for verts but you can pm one of those guys and find out.