differential gear change

[Tom Tarlazzi]

I have a 64 chevy c10 with a 12 bolt non posi rear and 3;73 gears. I want to go to 3;07 gears with my TH350 trans and replace bearings and seals in the process. I have never worked on a differential, and need all the help I can get.

[frankslagoon]

Hi Tom there are 4 different third members used in that rear end. 3:73 gears are the highest ring and pinion set you can use on that ser. third member. the next ser. goes from 3.42 to 3.07 I believe. Anyway. you can change the whole unit in there and use 3:07 gears but it probably will cost ya 500 bucks. Now if you have done any research you can see it's a bit tricky setting the gears up so they mess correctly. I would advice some assistance on first go around. Another option is to find a used rear end from a 63 thru early 70 with 3:07 gears and put new seals and bearings in.

[MySons68C20]

There is a wealth of info to be had here at this site and http://www.ringpinion.com/

[rickpilgrim]

You can get 3.08 but you'll need a different carrier. That change will take away a lot of low end.

[Captainfab]

If you change the carrier for your 3.07 gears, you will also need to change the spider gears in that carrier for the spider gears in your original carrier. This is because your '64 12 bolt has 17 spline axles, whereas '65 and up have 30 spline axles. You could also change the axles.

[frankslagoon]

Originally Posted by Captainfab

If you change the carrier for your 3.07 gears, you will also need to change the spider gears in that carrier for the spider gears in your original carrier. This is because your '64 12 bolt has 17 spline axles, whereas '65 and up have 30 spline axles. You could also change the axles.

Question Capt. can't we use the 17 spline side gears in the newer carrier ass.? I was glad to be rid of the old axles so never tried to use em. But ?

[frankslagoon]

Originally Posted by frankslagoon

Question Capt. can't we use the 17 spline side gears in the newer carrier ass.? I was glad to be rid of the old axles so never tried to use em. But ?

Sorry Capt. I guess that's is what your tryen say. Took awhile to sink in

[Tom Tarlazzi]

Thanks for the info. let me see if I got this right.along with ring and pinion, I need to get a series three carrier, but need to use 17 spline side gears to match my axles, as I want to keep the 6 lug pattern. can the series three carrier be bought with 17 spline gears installed?If not,can the 17 spline side gears from my 4 series carrier be installed in the 3 series carrier that I need to buy?

[frankslagoon]

That's what captfab was sayin. you can swap the spider gears
there is something to think about Tom. GM axles have (in my opinon) a very bad design. the axle shaft acts as the inner race for the axle bearing. so the bearings are always turning on the axle. The rearends are good for 2 or 3 hundred Thous. miles but the axle shafts wear where the bearing rides. this causes the outer seals to leak and waste your nice new brake job. you can buy a repair bearing that moves the contact surface out on the axle a little but I tried one and I don't think they will hold up well. The only right way to fix em is to have the axles welded up and turned to proper dia. 17 spline axles are a lot harder to fine than the newer ones. and older so if ya do find em there probably wore pretty bad. My 63 rear end had a million miles on it but really just needed a ring a pinion till I saw the axles.. I found a good 66 c10 rear end with good axles and switched the whole thing out in an afternoon. and all the c10s are 6 lug up to 70 which is where they changed the width

[Tom Tarlazzi]

I haven't pulled the rear out to work it yet,"cold garage syndrome",but judging from what I've seen so far, is age but not wear. The odometer has 32 thou. on it.The real miles could be way off that, but I found little or no play in joints that are 51 yrs. old. If the bearing ends of the axles look good too, it would be a waste not to use them.IMHO. As long as I could get a series three carrier without gears, or with 17 spline gears in it.I would't mind getting new spyder gears with the carrier as long as they were correct for the ratio and for the axles. Any suggestions as to who might be able to supply parts?

[ERASER5]

You would be out less money and less time if you swap the entire rear end. Just post that you want swap a 3.73 GM 12 bolt rear for a 3.08 GM 12 bolt rear and you will have about a hundred hands go up! 3.73 is the most desired gear out there, but the 3.08 will let you cruise on the highway very well. As a matter of fact, I have one to trade ( 1 coil spring, 1 leaf spring), but I am way too far away.

[Tom Tarlazzi]

I would be up for a swap,64' 3:73 12 bolt truck non posi coil spring rear, for same with 3:08 gears. I live in Moneta Va. 24121 which is near Roanoke Va. Thanks to all who posted info.This site has a wealth of info!