Rear Gear Swap: A Few ?'s

[Rabid Dog]

I have a 99 w/ a 3.8, and an 4L60E 4-speed auto.

My take off stinks. As I have an auto, I realise I probably have a 3.08 rear gear, or maybe a 3.42 at best. (doubtful)

Would I be happy if I have it changed to a 3.42? I figure this is a good gear for a nice mileage/weeee ratio. I would naturally have the ECU reconfigured for the swap, as I want to have it done for other changes. (ram air hood/air bag light, etc)

So my questions boil down too:

#1 How do I find out my actual ratio?
#2 How much more enjoyable is the swap usually?
#3 How much extra wear would this be to my transmission?

This would be one of many winter mods, during the cars upcoming hibernation.

[ October 28, 2005, 12:09 AM: Message edited by: Rabid Dog ]

[98Camaro3.8]

Check the codes on the door to see what gears you have now. 3.8 autos come with either 3.08 or 3.42.

GU4 = 3.08
GU5 = 3.23
GU6 = 3.42

G80 = LSD

[Rabid Dog]

Thanks 98, I'll do it in the morning. Any other info on my other questions? (assuming I don't have a 3.42)

[98Camaro3.8]

Car will be much more fun to drive. Wear won't be an issue, since it comes as a stock ratio. You just may use a little more gas on the highway, but not much. May also consider 3.73.

Computer tuning will be needed to recalibrate the speedo/odometer. Mail order tune from TSP would be the cheapest option if you can't find a dealer to do it or want the extra benefits of a tune.

[Rabid Dog]

Yeah, I wanted it to be done somewere else, other than at a stealership, and I looked at a very good guide on doing it myself, whoah.. no thanks. So like I said above, I'll be shipping it off to have those, and all the other changes I want done.

I've considered 3.73's, but most of my driving is on the highway, and I have a lead foot. Maybe when I get my reconfig, the car won't run so rich because of all the extra air from the lid and hood, and I won't notice a mileage difference as bad, even with 3.73's?

Wouldn't I need a different carrier going from 3.08's to 3.73's? I thought the biggest that would fit on the smaller one was 3.42's?

Thanks again, for the help so far. ;)

[98Camaro3.8]

There's isn't a huge change in mileage when comparing 3.42 with 3.73.

If you have 3.08 now you will need a new carrier. 3.08 is series 2 while numerically higher gears are series 3. Regardless if you choose 3.42 or 3.73, you'll need a new differential. Besides, you wouldn't want to put in lower gears with an open diffy.

[Rabid Dog]

Gotcha, so how much does a new (stock) carrier run? This is turning expensive! [img]redface.gif[/img]

Man, if I do have 3.42's already, something is seriously up with my car.

edit: I have a complete rear from my old 95 project, and I know it has a 3.23 gear. Could I just swap over carriers, then change gears?

edit2: What determines if one car gets a 3.08 or a 3.42 at the factory? Is there a speed package I'm not aware of? :eek:

Sorry 98, almost done.

[ October 28, 2005, 12:39 AM: Message edited by: Rabid Dog ]

[98Camaro3.8]

In the good 'ole days you could get it from SLP for $100. Now they're harder to find. If you're lucky you may see one for around that price, if not it could be $150 or more.

Yes, you could use the carrier from a 3.23 rear end. Just hopefully it's a limited slip. 3.42 - and especially 3.73 - wouldn't do great on an open diff.

[Rabid Dog]

I edited my post again.

Well the 3.23 rear I have IS an open diff, Just the two "spider" gears, that's all. No springs or similar. I learned about the rears innards, from swapping it over from drum to discs. So, it's not an LSD.

I assume that low gears aren't that stable in an open diff? LSD makes the rear more pricey to re-gear too. wow.

[Rabid Dog]

Well, I had GU4. So, yep 3.08 :(

Man, why would people put these things in a rear over even 3.23's? It's not like I plan to drive around at 120MPH. Who decide's these things? lol

So, as my other rear probably has an open diff, (per my last post?) and is a 3.23 rear, why wouldn't a 3.42 work in one as well?

I don't plan to drag at any time, just some light street fun. And to merge into traffic w/out pissing my pants on Knoxville roads.

[ October 28, 2005, 12:18 PM: Message edited by: Rabid Dog ]

[rhodeymark]

Going from 3.08 open to 3.42 open (in your other carrier) will give you a significant seat of the pants improvement. If your engine is running good you should find yourself scratching your right wheel a lot in situations where you used to feel like a slug.

[FunkZ]

Originally posted by Rabid Dog:
Man, why would people put these things in a rear over even 3.23's?

I think standard ratio on the automatic V8's was 2.73 gears, imagine if you had those.

[shenanigans]

want my opinion?

get a used 10-bolt of a v8 car with 3.42s.

I got a 3.42 rear, auburn diff, for $120 local.

you can't even find lsd for $120 usually. It also solves swapping carriers. And also fixes teh risk of not setting the gears in correctly which isn't "easy"

[Rabid Dog]

Originally posted by Rhodeymark:Going from 3.08 open to 3.42 open (in your other carrier) will give you a significant seat of the pants improvement. If your engine is running good you should find yourself scratching your right wheel a lot in situations where you used to feel like a slug.

Sounds good. Alot better than the mushy feeling in my arse now. Engine runs great, it's just got very little help from the rear.

Originally posted by FunkZ:I think standard ratio on the automatic V8's was 2.73 gears, imagine if you had those.

My truck has a V8, an auto, AND a 2.73 rear, I know all too well what that feels like. [img]graemlins/barf.gif[/img] But, it was built for towing from the factory, so I guess it's fine as it is. It's just a work truck anyway.

Originally posted by shenanigans:
want my opinion?

get a used 10-bolt of a v8 car with 3.42s.

I got a 3.42 rear, auburn diff, for $120 local.

you can't even find lsd for $120 usually. It also solves swapping carriers. And also fixes teh risk of not setting the gears in correctly which isn't "easy"

Sounds better. How many miles? What condition? I thought, I remembered you were fairly close to me.

Now, I'm still wondering about what 98 was saying, is there a problem with open diff's and 3.23's and later? Or, just in heavy abuse situations? I know that 7.5 10-bolts aren't known for being that good under stress.

[98Camaro3.8]

There's no problem but lower gears with an open differential will just lead to spinning when you get on the gas. An LSD will give you more traction when you step on it, instead of just sitting there spinning the passenger side wheel.

Since I have an M5, my car came with 3.23s; and also an open diff since I don't have Y87. One of the mods I did a few years ago was an LSD so that I can get off the line without spinning.