So what gives here

[425/409ER]

So I took the 4.88's out of the one 12 bolt and found I had some decent 3.08's on the shelf, so I thought they would be a good street gear. Pulled out the old stuff and then put the pinion in, got the ring gear cleaned up and proceeded to do the install into the housing. I got the carrier in and here's what I came up with, almost looks like the carrier is not centered in the housing to me. I have never in my life seen this, and I replaced the posi with a new 3 series carrier also. Look at how many shims are on the one side, it almost looks like to me that these gears are for a 2 series carrier but the gears came off a 3 series 12 bolt posi from a 69 Chevelle. Anyone ever see anything like this? I am stumped. Looking for my 4.10 wide gears to use if need be but they are not a street friendly gear for cruising down the freeway.

 

[MRHP]

Sum Ting Wong right there. Either wrong series case or gears!

 

[rsavage]

For 3.08 you will need a carrier that will handle up to 3.42. I am no expert but your existing carrier is probably a series 4 and you will probably need a series 3. Please check with someone who actually is an expert.

 

[425/409ER]

For 3.08 you will need a carrier that will handle up to 3.42. I am no expert but your existing carrier is probably a series 4 and you will probably need a series 3. Please check with someone who actually is an expert.

Funny thing is, the carrier that those gears came on is a 3 series + the new one I just bought is a 3 series carrier also. I have a friend who has an open 2 series carrier and he's going to let me try it to see if that's the problem, which I think it is.

 

[425/409ER]

So it was pretty nice out today so I figured I need to hunt down my 4.10 gears (I'm good at hiding things from myself) and moved some cars, parts around then found them in the trunk of my Firebird. Now I did not want this much gear in this project but after getting them in I think this rear end was made for a 4 series carrier and not a 3 series. The carrier does sit better (not perfect) and it all went together well with a good pattern. The 4.10's only had about 500 miles on them from past use. Looks like I need to hunt me up a 4L80E now to rebuild so I can cruise on the highway better.

 

[La Hot Rods]

Would take some work to put a 4L80 in one of these x frame cars. I do like those transmission though.
Could it be the ring gear is not for this rear end, maybe different 12 bolt?

 

[dakota tom]

Housings are all the same. Carrier is different. I think you have a 4 series carrier.

 

[dakota tom]

Ive never looked into the interchange, pickup carrier?

 

[dakota tom]

Could the 4.10 gears be an aftermarket thick ring gear made for a 3 series carrier if it takes a lot more shims on one side?

 

[dakota tom]

You need to get that carrier centered. With C clip axles if you don't the brake drums won't position properly.

 

[Skip FIx]

They make a "thick gear" and "thin" gear depending on the ratios and carrier.
12 bolts have a 2 series,3 series and a 4 series carrier. Most spools are 4 series.
I had to get a "thin gear" 3.73 for my 4 series spool in the Camaro.

 

[64ss409]

The passenger car 12 bolts and the pickup 12 bolts are not compatible. I believe the pickup 12 bolt carriers are wider.

 

[425/409ER]

Would take some work to put a 4L80 in one of these x frame cars. I do like those transmission though.
Could it be the ring gear is not for this rear end, maybe different 12 bolt?

This 12 bolt is for my other car, the Biscayne already has a 200R4. This 12 bolt came out of a Chevelle that I am using in my Camaro for a street rear end. The 4.10's went in without a problem and both axles worked perfect with the c-clips going right in. I am sure to get it perfect with the 3.08's I would need a 4 series carrier which I thought I had but was wrong on my checking out.

 

[Skip FIx]

https://www.hemmings.com/stories/article/gm-12-bolt-differentials

specs for the offset for each

GM 12-Bolt Rearend Guide. How-To Identify That Swap Meet Find

Finding a 12-bolt rearend is a great stroke of luck. But, if you don't know what version 12-bolt you're looking at, luck means nothing.

www.chevyhardcore.com

 

[63impaloligist]

They make a "thick gear" and "thin" gear depending on the ratios and carrier.
12 bolts have a 2 series,3 series and a 4 series carrier. Most spools are 4 series.
I had to get a "thin gear" 3.73 for my 4 series spool in the Camaro.

I think they make ring gear spacers for it too.

 

[425/409ER]

So today I got the perches welded on and the pinion angle set where I want it to be, but when I put the brake drums on the offset carrier crap reared it's ugly head today. I can see the LH axle sticks out more then the RH side does (because of too much side shimming) so off to the interweb I went a huntin'. I found two items of interest, one was some dude building a 12 bolt car rear end, and when he got to the carrier install he had the same problem I have. Seems the parts place sold him the wrong carrier, twice! and the other item I noticed was, would a 12 bolt "Truck" carrier work in a 12 bolt car rear end. Well it will, but the truck 3 series carrier will be off like a 4 series would be on a car causing the same problem I have. The article went on to say that, car posi's have one large opening and a small one on the other side. The truck carrier will be 2 large openings on both sides and that what's wrong here. Here's the kicker, the new one I just bought? is the exact same as the one in the 12 bolt now with my 4.10's. Seems that one is a truck carrier listed as a car carrier, lol I'll have to eat that one. Waiting on 2 people who have 2 good 3 series "car" posi's to test out. I ove messing with cars, makes it feel so good when you take it up the old poop shoot every now and then.

 

[Iowa 409 Guy]

The higher the tuition, the better the education........