Help choosing rear end parts

[Dleslie212]

Good morning everyone. I took apart my rear end conpletely yesterday except for the pinion. I want to go ahead and rebuild the entire thing, but I’ve never done this before and was hoping for a bit of feedback. Here’s what I have

77 K10
12 bolt
30 spline axles
11 pinion teeth, 41 ring gear teeth (3.73 ratio, correct?)


It currently has the G80 locker, but I’d like to install an actual locker on it. The ring gear has a few small chips on the ends of of a few teeth, but nothing major. I don’t mind replacing the ring and pinion, but I’m pretty intimidated by that. At the same time, I’d love to be able to say that everything in the rear has been replaced. What does everyone here think about installing a new carrier, but keeping the old ring and pinion? Should I be pretty safe reusing the old axle shafts instead of getting replacements?

Also, what kind of locker should I go for? I do a bit of off roading, but never anything hardcore. Most light or medium stuff, and lots of sand. I’d say 75 percent of my driving would be on the road, mostly just picking up the kid from school, or cruising around

[Matt Man]

Originally Posted by Dleslie212

Good morning everyone. I took apart my rear end conpletely yesterday except for the pinion. I want to go ahead and rebuild the entire thing, but I’ve never done this before and was hoping for a bit of feedback. Here’s what I have

77 K10
12 bolt
30 spline axles
11 pinion teeth, 41 ring gear teeth (3.73 ratio, correct?)


It currently has the G80 locker, but I’d like to install an actual locker on it. The ring gear has a few small chips on the ends of of a few teeth, but nothing major. I don’t mind replacing the ring and pinion, but I’m pretty intimidated by that. At the same time, I’d love to be able to say that everything in the rear has been replaced. What does everyone here think about installing a new carrier, but keeping the old ring and pinion? Should I be pretty safe reusing the old axle shafts instead of getting replacements?

Also, what kind of locker should I go for? I do a bit of off roading, but never anything hardcore. Most light or medium stuff, and lots of sand. I’d say 75 percent of my driving would be on the road, mostly just picking up the kid from school, or cruising around

I would rebuild the entire axle with a new ring and pinion and a master rebuild kit which includes new bearings and seals. 11 pinion teeth and 41 ring gear teeth is a 3.73 gear. As far as axle shafts go, I would pull them and look at the splines for damage or if they are twisted up. Also check your outer axle bearings and replace the seals while you are there.

For the kind of driving you do, I would strongly recommend a Eaton TrueTrac limited slip. This is a excellent posi that does not have clutch packs to wear out and you run just regular gear oil with no additives for the clutch packs found in other limited slip units. The TrueTrack uses a helical gear design. The g80 was marginal at best even when new I would ditch it. I have a TrueTrac in the front 10 bolt in my 81 k10 and it has been flawless and I wish I put one in the rear of my truck instead of the Detroit locker.

Rebuilding a rear end is not a task for beginners as you do need some specialty tools such as a dial indicator. I would strongly recommend you take the axle or truck to a shop to do the work. It is possible to do yourself but like I said not for a novice mechanic or beginner.

[Dleslie212]

Originally Posted by Matt Man

I would rebuild the entire axle with a new ring and pinion and a master rebuild kit which includes new bearings and seals. 11 pinion teeth and 41 ring gear teeth is a 3.73 gear. As far as axle shafts go, I would pull them and look at the splines for damage or if they are twisted up. Also check your outer axle bearings and replace the seals while you are there.

For the kind of driving you do, I would strongly recommend a Eaton TrueTrac limited slip. This is a excellent posi that does not have clutch packs to wear out and you run just regular gear oil with no additives for the clutch packs found in other limited slip units. The TrueTrack uses a helical gear design. The g80 was marginal at best even when new I would ditch it. I have a TrueTrac in the front 10 bolt in my 81 k10 and it has been flawless and I wish I put one in the rear of my truck instead of the Detroit locker.

Rebuilding a rear end is not a task for beginners as you do need some specialty tools such as a dial indicator. I would strongly recommend you take the axle or truck to a shop to do the work. It is possible to do yourself but like I said not for a novice mechanic or beginner.

The TeueTrac is actually one I had been looking at already, and I think you just solidified it for me.


https://www.summitracing.com/parts/dtl-913a315

Does the above look correct for my application?

As far as taking it to a shop, I really want to do this myself. The whole point of buying this truck last year was for the learning experience. I’m fairly mechanically inclined, so I’m confident I can get it done. Although it will probably take me waaaay too long to finish it correctly

[blazer2007]

If you do take it to a shop make sure he specializes in rear ends. I took mine to a shop where I thought he was good ,had a little howl on coast which he said it would break in and the pinion bearing went in a year. Do a lot of asking around and you will find one shop pops up more than others

[Matt Man]

Originally Posted by Dleslie212

The TeueTrac is actually one I had been looking at already, and I think you just solidified it for me.


https://www.summitracing.com/parts/dtl-913a315

Does the above look correct for my application?

As far as taking it to a shop, I really want to do this myself. The whole point of buying this truck last year was for the learning experience. I’m fairly mechanically inclined, so I’m confident I can get it done. Although it will probably take me waaaay too long to finish it correctly

Yes that is the correct unit for the TRUCK 12 bolt. Don't buy any parts for the 12 bolt car axle as they're different. In my opinion the hardest part is setting the pinion preload and dealing with the crush sleeve. See if you can buy a crush sleeve eliminator kit and look up videos on youtube on how to do it. Good luck and keep us updated lots of good help on this forum. Go slow and make sure the specifications are right on backlash, pinion rotational drag and teeth mesh. As you probably know, if you do not set up all these items correctly your rear end will eat itself alive.

[Dleslie212]

Here is what I’ve picked out so far. I’m hoping somebody wouldn’t mind going through this list and telling me if I have all the correct parts, or if there’s anything I’m missing


Differential -
https://www.summitracing.com/parts/dtl-913a315

Ring and Pinion -
https://www.summitracing.com/parts/mgr-gm12-373

Ring and Pinion Install Kit -
https://www.summitracing.com/parts/rat-3005k

C-Clips -
https://www.summitracing.com/parts/yga-33083

Crush Sleeve Eliminator Kit -
https://www.summitracing.com/parts/yga-55046

Carrier Bearing Kit -
https://www.summitracing.com/parts/yga-57010

[Matt Man]

Looks good. Nice selection of parts.

[Dleslie212]

I’m a week or two away from pulling the trigger on ordering these parts, but now I’m having doubts about the 3.73 gears. I’d rather not have to regear the front, but I also want to do the rear correctly the first time

I running a 350, 700r4 and 35” tires. I’ve read that I should be using a higher gear ratio... anybody have any thoughts on what I should do?

[mongocanfly]

I def wouldnt go any higher..with 35s and od, 3.73s would be as high as I would go...
With 3.73s, 35s, and a .7 od, your only turning 1629rpm at 65...
4.11s will get you 1795rpm....if I was gonna change that's more what I'd look at....

I went with 4.56s on mine...I wanted around 2000rpm at 65 with my LS/v4500
Heres a rpm calc thatll help you determine things...just fill in blanks at bottom of page...

http://www.csgnetwork.com/multirpmcalc.html

[Dleslie212]

Originally Posted by mongocanfly

I def wouldnt go any higher..with 35s and od, 3.73s would be as high as I would go...

Maybe I meant lower. I get confused with the terminology

[mongocanfly]

Gotcha...yeah higher means lower...haha....higher numerical = lower ratio....

Matt's covered it pretty good...building a diff isnt for the faint of heart...
can be very frustrating and requires some specialized tools as well
You'll need dial indicators, calipers, torque wrenches...both ft/lbs and in/lb...
A dial in/lbs torque wrench to check rotational torque..
A good press, bearing separators , setup bearings.. a case spreader is nice to have
And a lot of time and patience...

I agree with the tru-trac...but I like Yukon gears and kits...

[Dleslie212]

Originally Posted by mongocanfly

Gotcha...yeah higher means lower...haha....higher numerical = lower ratio....

Matt's covered it pretty good...building a diff isnt for the faint of heart...
can be very frustrating and requires some specialized tools as well
You'll need dial indicators, calipers, torque wrenches...both ft/lbs and in/lb...
A dial in/lbs torque wrench to check rotational torque..
A good press, bearing separators , setup bearings.. a case spreader is nice to have
And a lot of time and patience...

I bought all the tools needed this past week besides a press. There’s a machine shop near me that i can swing things by to have pressed if heating the bearings in the oven doesn’t work. I’m planning on ordering a second pinion bearing to sacrifice as a setup bearing as well. And it doesn’t mean much, but the past month I think I’ve watched almost every single YouTube video possible related to ring and pinion installs.

Anyway... what’s the deciding factor on if I should go with LOWER gearing in the rear? It drove down the freeway fine before. It didn’t feel like it had much oomph when stomping the gas, but I’m not going to be racing it or anything

[mongocanfly]

That no oompfff means you really need a lower gear...
If your riding around at 55 or less in od, your engine is just barely above a idle...like barely 1300rpm..
It all boils down to what you want...
thing is, if your going to the trouble and expense to do all the work, then optimizing your setup would be a good thing....my opinion
Off roading will be much more enjoyable with lower gears...
I've done quite a few riffs, and I still watch the vids ...its one of those things that if you dont do it every day it's easy to forget the little things..

[mongocanfly]

In your list of parts you have carrier bearings listed seperate...those are included in the kit..
I've not used ratech...I think it uses koyo bearings..
I'd highly recommend the Yukon kit...it comes with timken bearings..and the Yukon gears instead of motive

[Dleslie212]

Originally Posted by mongocanfly

In your list of parts you have carrier bearings listed seperate...those are included on the Yukon kit..

Good catch... thanks