Rear End Question

Pinknuts

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Just wondering if anybody knew if there were two different gear sizes for the LS rear end? If so what are the different gear sizes and which model came with what? I would guess the 5 speed v6 would be different than the auto v6 or v8. I just was thinking my car has the taller gears bc it was originally a v6 auto car. Thanks for any help.
 
There are 3 all depending on the model.. 3.07, 3.37, or 3.56.. the numbers probably aren't exact because I just woke up but you get the idea.. just look at the tag of the diff to determine the gears..
 
There are 3 all depending on the model.. 3.07, 3.37, or 3.56.. the numbers probably aren't exact because I just woke up but you get the idea.. just look at the tag of the diff to determine the gears..

Should be 3.31.

Manuals.... 3.07
MOST gen 1 V8s.... 3.31
ALL auto V6s, very early gen 1 V8s (there are very few of these) and all 2nd gen V8s...... 3.56
 
OK so I just need to look at the number on my diff? I just want to be 100% The car really feels like it has 307s with the 6 speed in there. I was hoping if I did have the 307s I could just swap in the 356s. But I might still just go the 8.8 route given the swap and all. Then I could put whatever gears I wanted.
 
my '00 v8 has 3.58s! neat! (edit: found the correct last number - looked like a 3 at first)
 
Yours should be 3.58 if it was originally an auto v6

Well dang those must be tall then. Bc I can go almost 60mph in 1st gear. They feel more like 307s but maybe the T-56 6 speed makes them even longer. If I do have 358s then I have to go to 8.8 if I want lower gears.
 
Depends what you want.3.58s are "taller" they'll get you going faster than 3.07s. but 3.07s are "longer". They may increase your top speed and improve mpgs. so it just depends what you're looking for.
 
I'm guessing you have 3.31's. Most gen 1 v8's have 3.31's (though some early model 2000's had 3.58's).

Only way to find out for sure is get under it and take a look. But I'm putting my money on 3.31's.
 
I'm guessing you have 3.31's. Most gen 1 v8's have 3.31's (though some early model 2000's had 3.58's).

Only way to find out for sure is get under it and take a look. But I'm putting my money on 3.31's.

He said his was originally an auto v6
 
He said his was originally an auto v6

Yes, when the builder was in here he said it was orignially a v6 auto putting you at 3.58 gears. However keep in mind that he did put a LSD(at least he said he did) and if he pulled a junkyard diff he might have a different ratio in there now.

The reason is feels so tall is because the gear ratios in the transmission. 6th gear is a vary tall 0.50 ratio. Combine this with a big cam and it's going to have less power in the low range.

One more thing to consider is the type of tune the car has. I believe the original builder said he went with a speed density tune from a turner. He never said he had it dyno tuned and you could probably gain a lot from a dyno tune as speed density systems usually are rich in the low RPMs and have less timing to be conservative so the engine won't run to lean because the tuner has to guess a lot unless he was provided data logging with a wideband O2 sensor.
 
Yes, when the builder was in here he said it was orignially a v6 auto putting you at 3.58 gears. However keep in mind that he did put a LSD(at least he said he did) and if he pulled a junkyard diff he might have a different ratio in there now.

The reason is feels so tall is because the gear ratios in the transmission. 6th gear is a vary tall 0.50 ratio. Combine this with a big cam and it's going to have less power in the low range.

One more thing to consider is the type of tune the car has. I believe the original builder said he went with a speed density tune from a turner. He never said he had it dyno tuned and you could probably gain a lot from a dyno tune as speed density systems usually are rich in the low RPMs and have less timing to be conservative so the engine won't run to lean because the tuner has to guess a lot unless he was provided data logging with a wideband O2 sensor.

Yes this all makes sense. I am thinking about just going and peaking under the rear end to see if the numbers are still on there. And I've never had a wideband O2 on there but would be curious. I will probably dyno it very soon and the place I dyno at logs with wideband also.
 

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