Another Gear Ratio Thread...

[navigator]

doesn't appear you can get anything over 4.10/4.11 for the 8.0 rear.
So yes, if you want 4.56 you'll need to upgrade to an 8.6 rear from a LWB or V8 model.

[Shdwdrgn]

Could someone please post of a cross-reference chart for gears/axles? For instance, I know that 2002-2005 models are interchangeable, and 2006-2009 models are interchangeable for the rear axle. I know the SWB has an 8.0" rear diff, and the SS and EXT's have an 8.6" diff that can be bolted straight up to the SWB models. I also know that if you want 4.56 gears, you need the 8.6" diff...

So what about the front axle? I'm specifically looking for a 2004 SWB, but it might be nice to put together a full reference chart of this stuff. What years and models should I be looking for? If I do a full differential swap on the front, are there any other models (like say a Silverado or a Tahoe) that would be a direct replacement part? What if I narrow my search to just the gears - what makes/models/years could I pull from?

Enquiring minds want to know!

[HARDTRAILZ]

the SS and EXT's have an 8.6" diff that can be bolted straight up to the SWB models.

The SS rearend is a semi-float 9.5 14 bolt actually. 4.10 gears with a G86 limited slip.

[Shdwdrgn]

Ack! OK that's different. Sounds good if you've got 35's, but my tires aren't that big!

So am I right in thinking the G86 is exactly the same as a G80, except in an 8.6" package?

[fishsticks]

Ack! OK that's different. Sounds good if you've got 35's, but my tires aren't that big!

So am I right in thinking the G86 is exactly the same as a G80, except in an 8.6" package?

While that seems logical, G86 is actually a clutch type LSD rather than a locking differential. Not really what you want for off road.

Kyle ended up having to change his carrier out when he swapped.

[Shdwdrgn]

So if I have a G80 axle (with 3.42) and an 8.6" axle (with 4.10), do I have everything I need to turn the 8.6" axle into the same type of locker as my current G80? Is there something specific I should look for in the replacement rear axle so I can get the beefier components without losing functionality?

[Conner299]

Depending on your offroading, if its heavy, sell the G80. Get an 8.6 with no G80. You'll need the open carrier in the diff in order to add a locker, of some sort, with no special tools required. If your offroading is light, get the G80. Then its just up to you, to decide if you want the 8.0, or the 8.6. Additionally, axles without the G80, are usually cheaper. Even more so if they are 3.42. Just as an example, my 1.5 year plan is to acquire an 8.6 rear axle with 3.42. About 200 cheaper than 3.73 and up, in my area. Then get the LockRight limited slip locker for the rear, and gearing that I want. Get a full locker for the front, and change the gearing, front and rear at the same time. Others can expound even better than I can this subject. I was all about getting a G80, until I learned how much of a pain they can be.

[Conner299]

And as far as I know the G80 is different between the 8.0 and the 8.6. I could be wrong though, I usually am.

Edit: Plus you need to get an axle with the same gearing as your diff. I only mentioned 3.42 cause that's what I already have. If you get a rear axle with 4.10s, you'll have to change the front gearing as well.

[Shdwdrgn]

Yep I'm aware of matching front and rear gearing... That's the plan. I have 3.42's. I need 4.10's. I do very light off-roading, but I tow a 5500 pound trailer up into the mountains, and most of my other driving is in-town, so the 4.10's will be very helpful.

I *thought* the rear axle was going to be an easy swap from an 8.0 to an 8.6 (might as well get the heavy-duty model if I'm swapping out components anyway). I haven't really had any problems with the way the G80 acts, but I'm trying to do this swap as cheap as possible. I figure if I do a full axle swap, it shouldn't be hard to resell my 3.42 G80 and get back some of my money. And I'm still searching for a solution to getting gears for the front...

[Cable810]

The only one I've found so far has over 215k miles on it.

Dang that sucks.

I was looking at a 8.6" with 4.10s and a G80 for $500 with only 50K miles. Now I found another with 13K miles on it No G80 still 4.10s for $450. Just sayin.

[Shdwdrgn]

Wait, now I'm confused... So there's a G80 available in the 8.6" rear axle, that is the same as the G80 in my 8.0" axle? And the G86 is just a different gearing, it has nothing to do with the size of the diff?

[djthumper]

The G80 in the 8" and 8.6" are not interchangeable. The G86 is in the SS and only limited slip.

[Cable810]

Karo had a diagram of the 8.6" and 8.0" G80. Can't remember where though...

[Cable810]

I hate to ask this but I think I have the right answer. I just want to be certian since I'm swaping the rear first. I can drive with different rations (4.10s rear 3.42 front) but If I'm to enguage 4wd I will run the chance of blowing the front diff.

[chevycrew]

Correct, make sure you drive in 2wd only.

[Cable810]

Ok. I was right then. Just wanted to make sure. Thanks!!

[tlouck]

I have a 2003 TB SWB with 8" rear GU6 3.42, I am in the process of trying to find a 8.6" GU6 3.42 without the G80 option. I would like to put in a eaton detroit locker with a 4.10 ratio. After reading all the threads here and else wear I am still a bit confused on what to do about the the front Diff. I know I need to re-gear the front to a 4.10 as well. my question is do I need to get a the entire front axle assembly from a EXT or can I re-gear my existing front diff? , do I just need to install new ring and pinion 4.10 gearing in the front? hopefully all that made since.

[mikekey]

I have a 2003 TB SWB with 8" rear GU6 3.42, I am in the process of trying to find a 8.6" GU6 3.42 without the G80 option. I would like to put in a eaton detroit locker with a 4.10 ratio. After reading all the threads here and else wear I am still a bit confused on what to do about the the front Diff. I know I need to re-gear the front to a 4.10 as well. my question is do I need to get a the entire front axle assembly from a EXT or can I re-gear my existing front diff? , do I just need to install new ring and pinion 4.10 gearing in the front? hopefully all that made since.

If my understanding is correct, the front diff is actually bigger than the rear. It's the same as S10's a 7.25 and you can purchase 4.10's for the front. You don't need to replace it. Just re-gear it.

I was confused too when doing my research, but I guess some of these guys grab the front dif anyways for spare parts. Then if yours breaks, you have another one to fall back on quickly. So might want to keep your rear axle too.

Someone correct me if I'm wrong.

[Conner299]

I guess that all depends on your mechanical abilities, and the time you have. If you feel comfortable setting up new gears, I'd say have at it. If you've never set up a ring and pinion before, it may just be easier to get a front diff already geared for 4.10's, and drop it in. As far as I know, the front diff on SWB and EXT should be the same.

[Cable810]

Fishsticks also had a 500 mile (4x4 engaged)break in period when he swaped gears in the front. Another reason I'm swaping the front Diff.