So I have my rear end disassembled and just bought a rebuilt 3 series gov loc posi off of ebay. I counted the teeth of my original ring and pinion and divided it and it came out to 3.08 with an open differential. The car is an 85 camaro z28. My friend gave me Richmond 3.73s and it is a thick ring gear. Now we are putting it all in and can't get the correct backlash because the ring gear is to thick. The original ring gear is a thin one. I checked online and I couldn't find a thin ring and pinion that fits a 3 series. So what should I do? I need to get the car back on the road ASAP so any feedback would be great. Thanks

 

Too bad you didn't ask this a week ago, I had a 3-seiries Gov lock opened up this weekend ! I'm wondering if you got a 2-series carrier off E-Bay ?? Sorry; but I don't have any other Gov-Loc units to inspect for ID purposes........


Here is a picture I took this weekend of the 3.23 Gov-Loc POSI unit.



For what it's worth,........ here's a pic of factory 3.73's on an Auburn POSI carrier.



The Auburn carrier body is 1/2". I don't know if the Gov-Lock is the same or not.

 

The thick 3.73 that you are trying to install is for a 2 series differential. You CAN NOT use it on a 3 series differential. There are many standard 3.73 gears available for this rear end with the 3 series differential. I don't know why you couldn't find one because they are much more comon than the thick one that you have. You can even find them in S10 trucks. http://www.ringpinion.com/b2c/Produc...rce=DiffWizard

I hope you are not going to be too hard on this Gov Lock. It will not stand much abuse. They are weak and just barely hold up to stock S series trucks.

 

When I looked at my gears today the 3.73 was by far the thickest ring and smallest pinon. Each step I took to another gear ratio was a step thinner to the ring gear and the Pinion got bigger.

Thickest to smallest was 3.73, 3.42, 3.23 and then the thinest was the 2.73. It seems like he's just comparing the 3.37's in hand to the 3.08's that were in the original rear end. No telling if it's made for a 2 or 3 series carrier based on the post,... the same is true for the carrier he bought. ( just cause he was told something doen't mean that info was accurate. )

big gear head: Is there any way to verify what series carrier he got ??

Camaro199677: any part numbers on teh 3.73 gear set ??


Now I feel like I need to check the numbers on my 3.73's !

 

I have measurements for them somewhere. I've lost track of some of that stuff since I closed my rear end business.

 

Shouldn't really need "measurements".

Here's what a 2 series carrier and a 3 series one look like. Note how the 2 series one the back of the ring gear flange is almost flat, but the 3 series one is strongly cone-shaped. That's because the flange is about .400" closer to the pinion CL on the 3 series since the higher the ratio, the smaller the pinion.



The material left at the bottom of a regular 3.73 gear, the most common (and also stock) kind, is roughly .400" thick, between the bottom of the "trough" and the surface of the carrier flange. The same place on a "thick" 3.73 is about ¾".

If you can even get the thing to go into your housing at all, you don't have a 3 series carrier and a thick gear. If you can even make the teeth mate, you don't have a 2 series carrier and a thin gear.

How far off is the backlash now? How much shim is in each side?

 

I think I get it,....

The area between the bearing & the ring gear flange is a coned shape on the 3-series Auburn carrier ? I feel the need to assume thats true for non-POSI too. I learned something new today




Is the same true about the Gov Lock units ??

 

Yes to all the above.

Think about it... "ratio" applies to not only the tooth count, but also, the gear diameters. BUT, since the ring is always the same size, then as ratio goes up, pinion dia goes down. So, as the ratio goes up, the ring has to keep getting thicker, so that it will mesh with the pinion. But, thick gears are more expensive to make, and have a yield problem; so at some point in the progression of ratios, they move the flange it mounts on over toward the pinion, and start over with the thinnest practical ring gear. In this model of rear, that happens between 3.08 and 3.23. It doesn't matter what brand of carrier it is; the same measurements apply. It would be possible to make a carrier that was flat but the flange was just farther over, but I don't think I've ever seen one like that. If they did, it would look like the bearing was stuck out WAY farther on a tall stalk, instead of looking cone-shaped. Still easy to spot, just ..... weird.

 

Junk the Gov-lock. Errr... sell it someone who thinks they actually want it. You don't. Trust us.

Get a Torsen from a 1999 to 2002 F-body with 2.73 gears.

Never look back.

 

jmd, he can't use the Torsen. He has 26 spline axles in the '85. He would also need to upgrade the axles to '90-'92 28 splines.

 

darn. Missed that.