Compatible rear ends

[Swampyankee74]

I have a 74 gmc 2 wheel drive. With the truck 12 bolt rear. I'm looking to either make this rear end posi or find a compatible rear end that is posi. I know changing the gears out is no simple job to do properly. And a compatible rear end would need the old spring hangers and shock mounts cut off and new ones welded on that match the truck. Anyone know what rear ends from other car have the correct width? Any suggestions from someone who has been through this before? What's my best path to take? Build the rearend I have or adapt a different rear end?

[JohnnyPopper]

Find out if your existing unit can be changed out to a posi.

Andy at A&B Trucks is pretty good with info and parts if you need them. 619-234-5171 Tell him John Michael referred you.

[Swampyankee74]

I did look into that. My rear end can be changed. I'm just a little nervous about doing it. One shim off and you can throw it in the trash.

[Swampyankee74]

I'll call that guy this evening.  Thank you for the number J popper

[JohnnyPopper]

Yes I agree! That's why I have never tackled rear ends and automatic tranny's in the 45 years of wrenching.

Definitely use a pro to do the work!

[Geezer77GMC]

I installed a Yukon locker in the 12-bolt of my 70 Chevelle. Easy job, no playing with shims, it replaces the spyder and side gears. Holds up very well behind a high powered big block and launches straight with slicks. Still alows the outside tire to overrun during turns and isn't noisy at all.

[Swampyankee74]

Don't you have to shim the pinion bearing off of the pinion gear to set the backlash from pinion gear to ring gear? And your locker I thing gets shimmed also? I could be wrong on the locker part

[zieg85]

Don't you have to shim the pinion bearing off of the pinion gear to set the backlash from pinion gear to ring gear? And your locker I thing gets shimmed also? I could be wrong on the locker part

If you are not changing the gear set the pinion depth is already set

[Swampyankee74]

Ok, that is good to know. I'm sure it needs ne pinion seal, she's juicy. Probably pinion bearings, axle bearings and seals. It's 49 years old. Gotta figure out how deep go.

[zieg85]

Ok, that is good to know. I'm sure it needs ne pinion seal, she's juicy. Probably pinion bearings, axle bearings and seals. It's 49 years old. Gotta figure out how deep go.

Pinion seal will have to have the pinion nut removed.  It has to put back exactly back the same.  Google it on Youtube to see if it is something you feel comfortable in tackling. 

[Swampyankee74]

I will do that! Thank you zieg

[Geezer77GMC]

Install of locker kit only requires removal of center pin that the spider gears run on, removal of the "C" clips to slide the axles out slightly to remove the existing side gears and install the kit. You obtain a hardened center pin if your original isn't already.
Locker vender can supply if needed. None of the shims are affected. Check this site's service manuals for the recomended pinion seal service procedure.

[VileZambonie]

What ratio do you have? A limited slip carrier is the way to go, don't go with a locker. You are in CT right? I do them.

[Swampyankee74]

Vz, my gears are 373's which I would like to keep that ratio. The rear end is a bone stock truck 12 bolt. Yes I am in Voluntown Ct.