Rear End Advise

[troyb_78]

I have an 84' Chevy C10 with 10bolt open differential with 3.08 gears. I am looking at changing my Carrier out to a posi. What posi's will fit my truck? Do I just want to get used posi or go with an aftermarket like the lockright positive locking diff in jegs for $230? Also what gear ratios would you recomend with a new350/700R4 combo on 31" tires. The truck is a daily driver, and sometimes pulls a bass boat.

[84 400]

Why 31's?
got a pic of the truck? i want to do the same in my 84 c10. i am sick of the 1 tire fire. Also i have the th350 i wonder if the rear end gearing would be diffrent for me

Great thread man i hope some one can help us out
84's rocik

[Grande Rojo]

I had a 700r4 in mine with 411 gears and 31" tall tires. It was just right with the overdrive. I now have 32" tall tires 353 gears and a th400.
Go with the eaton "posi" they are cheap and easy to rebuild.



Good luck

[Jonboy]

I woudl say either 3.42 or 3.73 for teh gears with overdrive, maybe 4.10 if you are planning on staying with the taller tires.

[Bishops Trucks]

I bought a Eaton unit with Moser Axels, Richmond Ring & Pinion 3:73 and all the bearings and seals for $1150.00 from Summit. Call either Jegs or Summit and talk to a tech. and tell him what you are looking for and they will steer you in the right direction. Good Luck!

[75sierraclassic]

I had been curious about the powertrax too. Here is some advice I bot earlier.

http://67-72chevytrucks.com/vboard/s...ight=powertrax

[Nolowrider]

I have the Lock-rite and I expierence no noise, clicking or jerking what so ever. I love it. Easy to install. I have 3.73 gears.

[cliffsta]

I googled an article a few weeks ago about gearing... a TH700R4 with 3.73 rearend gear has a quicker first than a TH350 with 4.56s... and the 700R4 of course is overdrive, for better highway mileage.

Here's the article. Someone else may have posted it before, but I searched for it, too.

http://www.enjoythedrive.com/content/?id=7088

Just some food for thought

I personally will be swapping in a 12bolt from the donor truck I'm getting. hoping it has 3.73s, if not, I'll put 3.73 limited slip in it, and I'll be going with 350/TH700R4 sometime in the next year.

[crossy]

3.42 -3.73 gears, lockrite or powertrax if you are not racing or reda$$ing a lot is OK and they are easy to install.

If you want durabiltity you need to go with an Eaton. The Auburns are not rebuildable and you must remove the ring gear and tranfer it to either of these units.

If you just want to see if you like a posi, even with the 3.08's then install one of the easy ones (powertrax or lockrite) in with your stock 3.08 gears. crossy

[piecesparts]

I changed my son's 86 open 10 bolt out for an axle out of a 79 3/4 ton truck 12 bolt posi unit. His 10 bolt was the 3.08 gears and the 700 R4 combo that we put in front of it was killing his gas mileage. We took his truck to a 3.73 gear ratio and actually gained 2 mpg in the process. We could have gone to a 3.42 gear ratio and might have done better. We bought a used axle assembly from a local salvage yard and had to update the carrier with a new one (we used an eaton unit) then we put "five on five" axles in the back after removing the 6 bolt axles. This all worked out fine, the only other thing we had to do was measure the driveline and change it's length a little due to the 12 bolt being a little shorter in housing length than the 10 bolt. I have the same setup in my 84 and both rear ends are a good combo, we get about 2500 RPM at 70 mph with our size of tires and the pick up and acceleration is strong. This combo with a 31" tire will give around a 2100 to2300 RPM at 70 mph (my guess).