Transmissions and Drivetrain Need help with your trans? Problems with your axle?

tranny/rear end question

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Old Dec 12, 2007 | 11:10 PM
  #1  
tchernobog's Avatar
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From: Charlotte/Wilmington, NC
Car: 1991 Z/28 1LE
Engine: 305 TPI
Transmission: 700R4
Axle/Gears: 3.42
tranny/rear end question

Alright, so I'll be getting a new engine soon, zz4, rated for 355 hp/405 ft-lb at the crank.

My car is a 6 cylinder right now. I've heard that the transmission was the same for 6 and 8 cylinder engines was the same, just with a different bell housing. Is there any truth to that? If not, will a 700r4 be strong enough?

Also, my rear end is non-LSD/Posi with drum brakes. Can I just buy an LSD rear end off the classified from an 8 cylinder and hook it up? If I get one with disc brakes will I need to change out the cylinders? Will that rear-end even be strong enough?

Thanks a bunch guys.
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Old Dec 13, 2007 | 01:27 PM
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Re: tranny/rear end question

The transmission is the same MODEL (700-R4); but it is not THE SAME. The bolt pattern where it bolts to the engine is different, and the 6-cyl is altogether weenier inside (fewer clutches in the clutch packs, etc.) It does not have a "bell housing", the case is one giant piece including that section. So, no, it will not work. You need a V8 one.

Best thing to do for a rear is to get one from a LS1 car (98-02 V8) with a stick shift; it will have disk brakes, posi, and a decent gear (3.42). It will work with your existing hydraulics except that if it comes from a car with 4-channel ABS you will have to re-plumb the brake hydraulic lines because instead of one feed to both wheels like your car has, it will have separate right and left feeds; and some minor creativity will be required for the parking brake.
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Old Dec 13, 2007 | 04:10 PM
  #3  
tchernobog's Avatar
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From: Charlotte/Wilmington, NC
Car: 1991 Z/28 1LE
Engine: 305 TPI
Transmission: 700R4
Axle/Gears: 3.42
Re: tranny/rear end question

Originally Posted by sofakingdom
The transmission is the same MODEL (700-R4); but it is not THE SAME. The bolt pattern where it bolts to the engine is different, and the 6-cyl is altogether weenier inside (fewer clutches in the clutch packs, etc.) It does not have a "bell housing", the case is one giant piece including that section. So, no, it will not work. You need a V8 one.

Best thing to do for a rear is to get one from a LS1 car (98-02 V8) with a stick shift; it will have disk brakes, posi, and a decent gear (3.42). It will work with your existing hydraulics except that if it comes from a car with 4-channel ABS you will have to re-plumb the brake hydraulic lines because instead of one feed to both wheels like your car has, it will have separate right and left feeds; and some minor creativity will be required for the parking brake.
Well, a shop is doing it, so would it be easier to just get a rear end from a 3rd gen camaro? I can have a rear end with say, 2.73 gears right? I will be doing quite a bit of highway driving back and forth to school, probably once a month or so, and 3.42/3.73 would probably kill my mileage even further.

And, will a stock tranny from an 8 cyl be able to handle the engine? If not, I'll just do one of the upgrades for it, but I'd rather know beforehand.

Yea, yea, I know, a shop is doing it. But it's a deal with my parents and they won't let me do it myself.
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Old Dec 13, 2007 | 05:37 PM
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Re: tranny/rear end question

I can have a rear end with say, 2.73 gears right?
Sure.

But then, why bother with all that motor?
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Old Dec 13, 2007 | 08:48 PM
  #5  
tchernobog's Avatar
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From: Charlotte/Wilmington, NC
Car: 1991 Z/28 1LE
Engine: 305 TPI
Transmission: 700R4
Axle/Gears: 3.42
Re: tranny/rear end question

Originally Posted by sofakingdom
Sure.

But then, why bother with all that motor?
Well, I'm going to have 2 sets of gears. I already have 3.73's from when my car had a 350 ( it was originally a 350 car, but I sold the rear end when that engine died. same for the tranny.)

I was going to just put in the 2.73's for school, and over long breaks, like christmas, spring break, summer, etc, put in higher gears.

I just wanted to make sure that'd be kosher, that it wouldn't chew em up.
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Old Dec 13, 2007 | 09:34 PM
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Car: Met. Silver 85 IROC/Sold
Engine: 350 HO Deluxe (350ci/330hp)
Transmission: T-5 (Non-WC)
Axle/Gears: Limited Slip 3.23's
Re: tranny/rear end question

Originally Posted by tchernobog
I was going to just put in the 2.73's for school, and over long breaks, like christmas, spring break, summer, etc, put in higher gears.
Setting up gears for occasions like that would be...well, more work than most people would care to be involved in.

JamesC
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Old Dec 13, 2007 | 10:53 PM
  #7  
tchernobog's Avatar
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From: Charlotte/Wilmington, NC
Car: 1991 Z/28 1LE
Engine: 305 TPI
Transmission: 700R4
Axle/Gears: 3.42
Re: tranny/rear end question

Originally Posted by JamesC
Setting up gears for occasions like that would be...well, more work than most people would care to be involved in.

JamesC


My breaks are a month long or so. Otherwise, I wouldn't do it.

But thanks for the help, maybe I'll get some lower 3's. Chevy has a 3.14 right?
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Old Dec 14, 2007 | 05:14 AM
  #8  
JamesC's Avatar
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From: Lawrence, KS
Car: Met. Silver 85 IROC/Sold
Engine: 350 HO Deluxe (350ci/330hp)
Transmission: T-5 (Non-WC)
Axle/Gears: Limited Slip 3.23's
Re: tranny/rear end question

Originally Posted by tchernobog
My breaks are a month long or so. Otherwise, I wouldn't do it. But thanks for the help, maybe I'll get some lower 3's. Chevy has a 3.14 right?
Gear set-up would run several hundred dollars a pop, so prepare for wallet thinning. No 3.14's.

JamesC
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Old Dec 14, 2007 | 02:14 PM
  #9  
tchernobog's Avatar
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From: Charlotte/Wilmington, NC
Car: 1991 Z/28 1LE
Engine: 305 TPI
Transmission: 700R4
Axle/Gears: 3.42
Re: tranny/rear end question

Originally Posted by JamesC
Gear set-up would run several hundred dollars a pop, so prepare for wallet thinning. No 3.14's.

JamesC



Oh, I've got the garage, the tools, and the know-how. I'd be doing it myself. I pretty much do all of my own work, the only reason I'm not doing the swap is because my parents are paying for it as a reward for getting a fat lot of scholarships, and they want a warranty with it.
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