ZR2 axle swap

[curtisb]

Hey guys, I've been reading through the old threads on this subject but wanted to ask a couple questions. from what I've read the axle swaps right in, no mods needed. But what about matching the front differentials gears to the rear? And how does the ZR2 rear end lock up? With this swap would i be getting all 4 tires turning at once in 4 low?

I want to make the change for sure. But I'd wait if i had to change the front diff and do a 2.5" Rough Country lift at the same time.

[_STUCKY]

Check the codes in the glove box to see what gear ratio you currently have.

GT4 Axle Rear 3.73 Ratio (Dup with 5X1)

GT5 Axle Rear 4.10 Ratio (Dup with GT8)

GU4 Axle Rear 3.08 Ratio

GU6 Axle Rear 3.42 Ratio

Your front axle is open. You should leave it open. Only 1 tire turns. It will be the tire without traction.

If your gears are 3.42, get a front axle that has 3.73 gears. The zr2 that the rear axle comes out of would be a good candidate.

[curtisb]

Thanks for tip. I'll check those codes. What does the up stand for?

[AVTekk]

If the ZR2 axle has a G80 locker in it, its really not very good for an offroad locker. It takes a lot of torque to lock up, youre better off installing an aftermarket locker to get a true locked rear. You dont need to do any gear changes as long as you find a ZR2 rear that matches your front diff.

[HenryJ]

If the ZR2 axle has a G80 locker in it, its really not very good for an offroad locker...

I have found it to work very well and prefer it for a daily driven vehicle.
If you are a rock crawler or dedicated toy, then by all means install a spool or other high performance locking differential. Although if you are to that point, you really need to consider the front differential and what changes need to be made there to lock it.

[curtisb]

I'm GU6, so I have the 3.42. The ZR2 probably didn't come geared any smaller then the 3.73, but i wouldn't really want to go through the trouble of doing the swap and not getting the better gearing for larger tires and better 4x4ing.

On the bright side i can do a slow accumulation and gather all the parts i need, then buy the RCL.

[LonestarZ]

The ZR2 only came geared as a 3.73

[Horsehammerr]

Get a matching ZR2 front differential and be done with it.

[curtisb]

That's the plan, hope i can the front diff and the rear axle (zr2) with decent miles. All of my projects are going to be drawn out now that I'm expecting a little one.

[uwwsquirrel]

Yes sir - I'm in the process of doing this as well. I found a '96 iron front diff, and a '99 ZR2 rear in the yards a little while ago - just dropped them off today at Pro Gear to swap in a donor 3.73 ring and pinion for the front and complete inspection for the rear. I'll let you know how much that procedure runs once I get them back so you have an idea of the shop costs if you decide to go that route.

But it would probably be much cheaper just to find a front diff that was already geared to 3.73 as Horsehammer said. I paid $58 for the donor aluminum 3.73 diff and $58 for my Iron 3.42 diff from the Pick Your Part yard. They're out there.

Congrats on the little one BTW.

[ApproachMedium]

OK so getting my ZR2 axle next weekend hopefully. I have an 02 crew. The donor vehicle is a zr-2 blazer. I am also getting the sway bar as id like to have the better handling along with it too.


I looked online and the shock part numbers are different. Whats so different about them? Has anyone tried putting the ZR-2 bilsteins on their crew after the axle swap? Curious to hear what the results may be.

[HenryJ]

You will continue to use the crew cab shocks. ZR2 shock are different because the spring packs and different the mounting points. The shocks a a couple inches longer. Not very useful for us unless you drastically change the spring packs. The track bar on the ZR2 gets in the way of the shock on the crew cab. Hopefully someone did not confuse the panard bar with the sway bar. A sway bar can be installed as long as you get the frame brackets too. The panard bar can not be installed.

IIRC, you are going for the Low-n-handling. The rear sway bar is a good idea. Look for the Hop-shock too. Rare, but I thought it would be nifty.

[ApproachMedium]

What is the panhard bar do? Im pretty sure this is a sway bar, at least from what the photos show thats what it looks like. The donor is a Blazer which would have had front and rear sway bars. The sway bar on the blazer was mounted forward of the axle instead of behind it as it is on all 2 door blazers (what I read online at least). And since its a blazer, the frame brackets are part of the frame so I need to pick up a pair from S10 warehouse on ebay. They make brand new fancy welded ones.

Handling is what I am aiming for. Adding the rock sliders made my CG lower which was good, but once I put the body lift on that kind of got negated a bit, and then the 30 inch tires. Trying to control a bit of the body roll, yanno with all these darn Jug handles and tight on and off ramps we have out here in Jersey. LOL.

[HenryJ]

The Panard / track locator bar on the ZR2 is an axle locator. Keeps the axle from shifting side to side with the increased ride height.

Do you have the rear spacers yet? Wider track will help a little. The "Hop-shock" Will help axle wrap on a launch. If that is not in the works, you might think about the Roadmaster booster kit to firm up those mushy rear springs. Mushy is good for articulation. but not so much for handling.
I will assume you already went with the energy suspensions poly bushings up front?

[ApproachMedium]

No rear spacers yet. Ill have to look in to the hop shock. The springs on the back of my truck are actually pretty firm, and they dont look like the factory springs. They were new looking when I bought the truck. They have quite the kick over speed bumps and have zero sag with anything i have ever put in the bed of this truck.

I have the energy poly bushings in the works for the front. I bought the new torson bars but I havent had the money to have them and the bushings installed yet. Now that Im doing this rear axle I think I am going to get the energy bushings for the rear as well I think. That should transform the truck all around. Everything in the front right now is original and with 266k they are quite shot looking and the front end ride shows it.