G80 swap questions.

[kennythewelder]

So what all does it take to do a G 80 swap into a 97 2WD 5.7L 4L60E extended cab. Can I swap axle shafts, and keep my 5 lug rims. I guess I could always pull the axle shafts, weld up the lug bolt holes, and re drill them to the 5 bolt pattern. I do work at a machine shop, after all. I need to do this on a budget. As for bearings, we have 4 presses at work, and press bearings all of the time. I guess I would also need to put new clutches in the G 80? Also if anyone has the RPO codes for the gear ratios That would be good too. My truck does good with 342s now, or 373s would be good too, but I would want to keep it to one of those 2 gear ratios. Any thing I should look for or stay way from. Thanks in advance for any help.

 

[Tavi]

GT4 is 3.73, GU6 is 3.42 Do you plan to swap the whole housing or just the differential and gears?

As long as your housing is the same length and style (2wd to 2wd/4wd to 4wd, 8.5 vs 9.5) you should be able to use your axle shafts. I haven’t taken apart a 5 lug 2wd. But as far as my research all GMT400 8.5s are 30 spline.

Look out for? Generally G80 are frowned upon and avoided. Especially when you plan spirited driving.

 

[kennythewelder]

GT4 is 3.73, GU6 is 3.42 Do you plan to swap the whole housing or just the differential and gears?

As long as your housing is the same length and style (2wd to 2wd/4wd to 4wd, 8.5 vs 9.5) you should be able to use your axle shafts. I haven’t taken apart a 5 lug 2wd. But as far as my research all GMT400 8.5s are 30 spline.

Look out for? Generally G80 are frowned upon and avoided. Especially when you plan spirited driving.

Yea I got a lead foot. I think I can do a powertrax no slip for about the same price as it would cost me to do a G80 swap. Just trying to figure out my best options.

 

[NightRunner]

Generally G80 are frowned upon and avoided. Especially when you plan spirited driving.

So let me ask this since it seems like a decent place to ask. Say I find a 2WD G80 and swap the diff and gears over. Would this be fine for towing and very occasional off roading? Just curious where they stand between Subaru’s Glass Transmissions and Dollar Store LSD

 

[redfishsc]

You blow up a G80 by doing burnouts and donuts. Every video I've ever seen of someone grenading a G80 is when they are doing those things. It seems like the G80 tries to engage with the wheels spinning way the hell faster than the intended 20mph or whatever.

If you are just towing or doing general rock/hill crawling, I don't think the G80 is any more brittle than any other carrier. Mine had 200K miles on it and looked just fine, I just wanted an Eaton Truetrac in it (great decision, by the way, no regrets). It will behave like an open differential until (theoretically) there's some wheel slip. Just don't let that wheel slip be obscene RPM.

The G80 is designed to help you get the truck off a slippery boat launch or maybe get going at a stoplight with wet roads. It's NOT a good hotrod carrier.

 

[redfishsc]

Kenny, to answer your original question. Unless you do a lot of driving where traction is lost (sloppy rainy climate, or you trailer a boat down algae covered ramps, etc) then you aren't likely to ever noticed that you even have a G80 in the back, except for perhaps the occasional clunk sound.

Your simplest bet is to find a 5-lug rear axle that has the G80 RPO code and yank the whole thing and put it under your truck. They are out there. I know most, if not all, the Suburban LT's had them (both of my 99 Suburban LTs came with G80). I also think the Suburbans come with 11" drums instead of the common 10" drums. Please don't take this as Gospel but I think a Sub rear end will fit your truck.

What I do know is that the K1500 4WD trucks are usually 6 lug and their rear ends aren't a direct swap.

As for gear ratio, you may notice the 3.73 will make the truck accelerate a little nicer, make it feel like a "lighter" truck. I know that going from 3.42 to 4.10 in my 2wd Suburban was a GREAT upgrade. 3.73 would not be as significant as a jump.

Oh, and if you do go 3.73, your speedometer will be utterly wrong. You WILL have to find a tuner to tweak it if you want the speedo working at all--- I had to. My speedo was completely useless, it said I was going like 98mph when I was going 65.

 

[kennythewelder]

I do have a Jet programmer that I can reset the speedo with. And thanks for all of the info guys. Keep it comming.

 

[df2x4]

I would not go to all of this effort just to "upgrade" to a G80. They're super unpredictable and not much good over 20MPH or so as they automatically unlock with any kind of wheel speed. I agree that they're not as fragile as some people make them out to be, but they still suck. Both of my trucks have them and they drive me crazy.

Personally if it were me I'd throw a TrueTrac or a Detroit Locker in depending on how you want the truck to behave. But you say you're trying to do this on a budget so in that case I'd look into a mini-spool. I researched it a little bit a month or two ago while I was looking for a cheap upgrade to get away from the G80... From what I gathered you can install a mini spool into your existing open carrier in place of the spider gears pretty easily. Using the factory carrier means you don't have to mess with any other parts like you would with a full spool, C-clip eliminators for example. This would lock both of your drive wheels 100% of the time, similar to welding the spider gears. You can pick up the mini spool for around $80.

If you want the ability to unlock during low speed cornering then you could go with a Powertrax... But at that point you're getting real close to $500 territory, which means you're not far off from just buying a nice Eaton carrier.

 

[Tavi]

So let me ask this since it seems like a decent place to ask. Say I find a 2WD G80 and swap the diff and gears over. Would this be fine for towing and very occasional off roading? Just curious where they stand between Subaru’s Glass Transmissions and Dollar Store LSD

The G80 (Eaton MLocker) isn’t a horrible design in stock driving. There are a few who have claimed to have blown them up while babying their truck. Wasn’t there, don’t know the history. The flaw of the design is it is triggered by wheel spin, then suddenly locking. Knowing Newton’s laws explains why this can be a bad thing. Adding power and tire size will exasperate the result. My experience has been with a stock TBI truck that couldn’t spin one tire. Much less get both spinning. And the 14BFF, Which are much beefier. I would say you should be fine towing. But decline to comment on the off road aspect.

I would not go to all of this effort just to "upgrade" to a G80. They're super unpredictable and not much good over 20MPH or so as they automatically unlock with any kind of wheel speed. I agree that they're not as fragile as some people make them out to be, but they still suck. Both of my trucks have them and they drive me crazy.

Personally if it were me I'd throw a TrueTrac or a Detroit Locker in depending on how you want the truck to behave. But you say you're trying to do this on a budget so in that case I'd look into a mini-spool. I researched it a little bit a month or two ago while I was looking for a cheap upgrade to get away from the G80... From what I gathered you can install a mini spool into your existing open carrier in place of the spider gears pretty easily. Using the factory carrier means you don't have to mess with any other parts like you would with a full spool, C-clip eliminators for example. This would lock both of your drive wheels 100% of the time, similar to welding the spider gears. You can pick up the mini spool for around $80.

If you want the ability to unlock during low speed cornering then you could go with a Powertrax... But at that point you're getting real close to $500 territory, which means you're not far off from just buying a nice Eaton carrier.

A spool used on the road will eat the tires, and cause the suspension to flex in ways it wasn’t designed. It also tends to bend axles.

 

[df2x4]

A spool used on the road will eat the tires, and cause the suspension to flex in ways it wasn’t designed. It also tends to bend axles.

I'm aware that it's not ideal for longevity, but plenty of folks do it with no major problems. I mainly suggested it due to the budget concerns. Other than welding the spider gears, a mini spool is the cheapest option I'm aware of to lock the rear wheels with an open carrier.