what size is it?
#1
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Car: 1985 IROC Z28
Engine: 355 aluminum heads, comp 294 magnum
Transmission: 700r4 with B&M Mega Shifter
Axle/Gears: Motive 4.10's
what size is it?
hey guys! I have an 85 Iroc with the 700r4, i know the car has 3.23 gears but what size is the rear end itself? I am shopping for gears for my car. I am either going with a 3.73 or 4.10 and i don't know what size the rearend. and info!
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Re: what size is it?
If it has 10 bolts holding the cover on, it's the 7.5" / 7.625" one. (same thing)
If it has 9 bolts, it's the 7.75" one.
If it has 9 bolts, it's the 7.75" one.
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Car: 87 IROC L98
Engine: 588 Alcohol BBC
Transmission: Powerglide
Axle/Gears: Ford 9"/31 spline spool/4.86
Re: what size is it?
The 10 bolt is a GM corporate diff. The 9 bolt is made by Borg Warner in Australia. Parts between the 2 diffs are not interchangeable.
If you have a 10 bolt, it has a 7.5" ring gear. Around 1986, GM upgraded to 7.625" but everything else is still the same. A fourth gen diff is 7-5/8" but it's still called a 7-1/2". When we refer to these tiny 10 bolts, it's always called a 7.5" even though it may have a 7.625" ring gear in it.
A 700R4 and 4.10 gears are a bad combination. The low first gear is too much for the deep gears. It's fun stoplight to stoplight but that's about it. A better combination is 3.73 gears.
If you have a 10 bolt, it has a 7.5" ring gear. Around 1986, GM upgraded to 7.625" but everything else is still the same. A fourth gen diff is 7-5/8" but it's still called a 7-1/2". When we refer to these tiny 10 bolts, it's always called a 7.5" even though it may have a 7.625" ring gear in it.
A 700R4 and 4.10 gears are a bad combination. The low first gear is too much for the deep gears. It's fun stoplight to stoplight but that's about it. A better combination is 3.73 gears.
#4
Re: what size is it?
You need to read the 10 bolt sticky before you start ordering any parts. There is a lot of information in that sticky that will educate you and keep us from having to answer questions that we have answered many, many times before.
https://www.thirdgen.org/forums/tran...-10-bolts.html
https://www.thirdgen.org/forums/tran...-10-bolts.html
#5
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Car: 1985 IROC Z28
Engine: 355 aluminum heads, comp 294 magnum
Transmission: 700r4 with B&M Mega Shifter
Axle/Gears: Motive 4.10's
Re: what size is it?
thanks guys!
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