nonG80 to G80 swap

[fishsticks]

Donny... isn't there also a left/right shim adjustment to the left and right of the carrier bearings? Maybe the shim is under the ring gear?

Our ring gears aren't shimmed to the carrier, or at least mine wasn't. I haven't had a ton of rear ends apart, but the installation kits I've seen always seem to have shims for the pinion.


Paging Mr. glfredrick.

[Trail X]

#11 isn't on compnine, but I believe it's the shims.

[fishsticks]

I think those are just thrust washers. They had no paint markings on them like any of the other measured pieces do. (ie the thrust block)

[Trail X]

According to the FSM, our axle has both pinion depth and backlash adjustment shims. Item 11 is listed as the differential bearing backlash shim.

Also, in reading through the FSM, it states that you should ensure to keep your left bearings/shims/bearing cap on the left during reinstall, and vice versa.

[fishsticks]

According to the FSM, our axle has both pinion depth and backlash adjustment shims. Item 11 is listed as the differential bearing backlash shim.

Also, in reading through the FSM, it states that you should ensure to keep your left bearings/shims/bearing cap on the left during reinstall, and vice versa.

Good thing I'm OCD about keeping track of that stuff then...

[TangoBravo]

Where can I get one of these fsm? local parts store or is that a dealer item?

[Philberto]

FSM = Factory Service Manual


= from the factory


= you need to get it from a dealer.

[TangoBravo]

ok thanks I will have to see what that cost because it sounds like a great tool to have. Would really help alot.

[The Roadie]

No need to enrich the dealer for a manual they won't stock. HELM INC.

Ebay or order direct from Helm.

[TangoBravo]

makes sence thanks roadie

[Trail X]

They aren't really cheap, but they have the most accurate and in depth information... I'd buy one for all of the vehicles you plan to maintain yourself.

[AlekG]

Yeah thats why I was aking about gear ratio, I have the 3.43 I think is the ratio it is not the 3.73 or 4.10. So i figure that down the road I plan on tires as big as 35's or would at least like the possibility of 35's so I figure if there is a better gear for tires like that then I would rather swap over gears while im in there then do it all over again down the road.

Taller the ratio the better, to a point... 4.10 is your best bet for 35s

Yes, 4.10 would be the best from OEM availability but ... even 4.10 is not really enough for 35s, its barely enough for 33's according to most charts out there. By my SOTP gauge, the 4.56 gears I had installed brought the Trailblazer back to original power to the ground. And by those same charts, that gearing is in the "sweet" spot for 33's. Ideally 35's should be complimented with even taller gearing, but alas, not currently possible due to a lack of R&Ps for the front.

If you are going to the trouble of swapping the front gears anyways (a BIG deal), then maybe consider 4.56 gears. But to do that you will need to get an EXT or V8 complete rear axle that uses the 8.6 inch gears (mind the crossover year).

You can get all the info on my build here, from the early R&D to the final install.

Oh, and then you can consider a better diff than the G80 as well.

[glfredrick]

If you're just installing a new carrier, you should have it re-shimmed. There are machining tolerances between the bearings and the ring gear that differ between parts. Installing a new one should prove to be very close to correct, but if you want the diff to be robust, you should at least check the tooth contact pattern.

It is not just that you "should" have it re-shimmed, you MUST have it re-set-up or the gears will likely dynamite!

The cost of setting up gears if you are not equipped to do so yourself far exceeds replacing the entire axle assembly.

If replacement of the entire axle is possible, go that route.

Same up front. If you can find a 4.10 carrier, go that route and swap out everything instead of trying to install new gears. Many shops will charge between $250 - 500 to set up one axle. It is a time consuming process.

If 35" tires are in your future, even 4.56 is a tad low. We run 4.56 with 33s in most of our builds and those gears are not in any way too steep for 33" tires. I don't believe that a 4.56 gearset is available for the front axle, however.

With 3.42 gears and 35" tires, you will never again see OD except at freeway speeds of over 70. If you can live with that okay, but most people can't. Your crawl ratio will also suck. You won't be able to slow down enough on trails that require 35" tires. If you are just running on the street, you may (may!) get away with it, but your truck will be a slug that passes everything except a gas station.

My worst tire/gear ratio setup was 3.73 gears with 38" tires. The truck was setup for sand/mud and I wanted to be able to spin the tires fast in low range. I could hit 85 @ 6000 rpm in low range and had 550 hp big block pushing me. Truck was fast and mean, but barely drivable in high range. It idled at 55.

[TangoBravo]

Yeah it sounds like I will just swap everything from one truck to mine, I do not want a street queen, that's more or less what it is now as most trail around here really require bigger tires. In order to do that I need to be lifted, so let me slap myself back to reality lift my truck first then get bigger tires then worry about the swap. Thank you guys for all your help, I really am liking the challenge of the Tb it's not like you can just pull stuff off the shelf of the local 4x4 store(yoter's,jeeps) you really have to put stuff together with these and that is forcing me to read more about the truck and learn as apposed to just buying a 6inch lift and slap it in. I am glad people like yourself have gone before me but not so many that we are common it's cool.