My '78 needs a new rear end

[Corts60]

Went out to the garage today and the front pinion seal on my rear diff leaked gear oil all over the floor. The rear end is sloppy anyways and probably has around 280K on it.

I was wondering if anybody knows of a good axle repair shop in Portland, OR. I was thinking of maybe taking it to a 4WD place. I want to install different gears and have the whole thing rebuilt. It is a 1/2 ton 12 bolt w/ 3:40's currently. I want 3:73's.

All suggestions welcome!

[gchemist]

You can rebuild it yourself. Setting the pinion and ring lash is the hardest. You can find someone to set it for you. If it's set incorrectly, the ring and pinion could be ruined in a few miles. Ask your local racers who builds their axles. Search around Craigslist. You can find someone that works at a shop do it off hours.

[justcuz]

Cort,

Randy's Ring and Pinion rebuild kit and gears. I am sure you have the skills to do it yourself and their tech line is awesome. I know one guy who sent them online photos of his backlash setup and the guy looked at them and responded with corrections. Also youtube is your friend here also for setting up the rear axle.

An up grade would be a semi-float 14 bolt out of a square 3/4 ton. Have the axles and drums re-drilled for the 5 on 5 bolt pattern. If you got real lucky you could find a SF 14 bolt out of a wrecked 454SS pickup that has the right bolt pattern. You will have a bulletproof rear axle that will outlast the truck. Ford used a semi float Dana 60 that had a 5 on 5.5 or 8 lug pattern that would also have to be re-drilled.

I bet you could find a square body 3/4 ton semi float, have the drums and axles re-drilled for 5 on 5 and maybe the center of the axle turned down to the 12 bolt size and it would cost less than rebuilding the 12 bolt.

You may find a 1/2 ton 12 bolt from a square (maybe even 67-72) 4x4. Just switch out your axles and drums and your in business.

If you have the equipment you could re-drill the axles and drums at the shop, then send the axles out to have the centers turned down to the 12 bolt size, so your wheels fit.

I know the 14 bolt SF comes in newer 88-98 trucks also, but they are 2 different widths (2wd and 4wd) and the spring perches do not line up. A square rear axle is a bolt in, with the exception of the u-joint. It may require a conversion u-joint unless the 12 bolt pinion fits the 14 bolt.

Ring gears will have the ratios in them 41-11 is 3.73 and 41-10 is 4.10. I think either would work well for you as the 4.10 is only 10% faster rpm wise on the engine.

That's about it, I've pretty much exhausted my memory of options. I will check the pinion spline count and OD and see if it will fit and post it later for you.

Regards,
Chris.

[justcuz]

12 bolt 8.875 ring gear
14 bolt 9.5 ring gear
Dana 60 9.75 ring gear

12 bolt found in;
69-81 Blazer
64-81 C & K10 pickup
65-81 C & K10 Suburban
65-81 G10/20 Vans

14 bolt found in;
81 up C & K20 trucks and GMC C & K2500 trucks
81 up G30 vans and cube vans
81 up C & K20 and GMC C & K2500 Suburban
88 up C & K2500 extended cab

Dana 60 found in;
67-69 F-100 5 lug
80-85 F-250 8 lug
67-75 1000 & 1100 pickup and Travelall 5 lug
69-73 Jeep J-20 5 lug

These are all semi-float axles in truck applications only.
The Dana 60 SF has 30 or 35 spline 1.50 diameter axles
The 14 bolt SF has 33 spline 1.38 diameter axles
The 12 bolt SF has 30 spline 1.28 diameter axles

Personally a 35 spline Dana 60 is what I would build and install.

[justcuz]

Found some interesting info on Isuzu 4H diesels today too. Looks like up to 500 Ft. Lbs. torque and about 800 lbs engine weight. SAE 3 bell housing.

[Corts60]

You're the man Chris! I will look into these options. One thing I know for sure is that the shock perches were welded in a different location when the truck was lowered by the original owner back in 1980. So whatever axle I get I will have to deal with that. I'm trying to find some time to get out in the shop and rip that thing out. So busy lately.
Posted via Mobile Device

[justcuz]

Shock perches on anything other than a GM rear end would have to be moved or modified anyway, so no biggie.
Measure your springs across the rear axle outside to inside will give you your mounting width for springs. Most of the 60's to mid 70's trucks were real close.

[andrewmp6]

You can get a axle swap kit from ruff stuff its spring perches u bolts and top plate and the shock mounts.