Forced Induction Superchargers | Turbochargers | Intercoolers

what gear for turbos?

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Old Mar 2, 2008 | 05:55 PM
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Default what gear for turbos?

im putting a turbo in the car what size gear do you guys think the rear end should get???
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Old Mar 2, 2008 | 06:32 PM
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Most guys on here say to get the lower gears like 3.42 or lower....3.23,3.08 but I see quite a few cars on the boosted lists in this forum running 3.73 and still running some great times at the track even with autos. Usually you would want a bit lower gears in autos..talking lower numberically..
I am torn in my car between 3.54 and 3.73. The 3.73 would be nice off boost and good for the clutch and its a pretty heavy car like 4000 pounds. The 3.54 might help the turbos load up a bit better. I am m6 now but might go auto later. If do go auto it will for sure be overdrive auto. The dana 60 I plan on getting has only 3.54 for lowest choice.
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Old Mar 2, 2008 | 06:37 PM
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what trans??
check out this
https://ls1tech.com/forums/forced-induction/739123-turbo-m6-what-rear-gears.html
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Old Mar 3, 2008 | 04:01 PM
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if i had a turbo, i would probably end up with 3.73s. I would think it would be good at the track and should still be decent on the highway. But I'm sure it's not considered the optimal gear for a turbo car.
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Old Mar 3, 2008 | 04:14 PM
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3.23s for an automatic and i believe a 3.42 for manuals

keep the stock gearing for turbos
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Old Mar 3, 2008 | 06:25 PM
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I think it all really depends on what tranny you run and what gearing is the trans. you may have a low gear in the trans and have a high gear in the rear end or vise versa. I'm building a twin turbo LS1 for my 77 trans am, using a th400 but i have 4.56 gears in my car. It's back halved with 32x16x15 slicks. But i think it all depends on what trans you go with and what gearing is in the trans.
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Old Mar 3, 2008 | 06:34 PM
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Well if you check that boosted list in this forum you wil see what I have seen. Many many very fast cars are running at least 3.73s.Don't really see that many really fast cars in those lists running gears like 3.08s or lower. Now it might just be a case of the lower gears feel faster but in reality aren't. I would like to see some magazine take a 9 inch and swap in various gears in a turbo car and see what difference it really does make. And while auto cars may not mind the lower gears like 3.08s then clutch cars usually seem to like higher gears like 3.42 and up to help get our heavy pig cars moving.Would also think the higher gears are easier on the clutch. So far I think the lower gears for turbos is pretty much a myth until someone definitively proves it. Also while these gears like 3.08 might be fine on boost how doggy is the car going to be off boost and off boost can be under 4000 or even higher rpm with some turbo setups.
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Old Mar 3, 2008 | 06:39 PM
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Just like any car, you gear it to hit top rpm at the traps. I wound up with a 3.00 because I'm going 146 mph at 6200 rpm on a 26" tire. It just so happens that turbo cars usually run allot of mph and the engine peaks early, so you wind up with a tall gear. Nothing to do with spool-up.

Mike
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Old Mar 3, 2008 | 07:01 PM
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I'm running 2.75's and a 26" tire and manage to do alright.
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Old Mar 3, 2008 | 07:15 PM
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I see alot of street turbo cars that were 4.10s before turbo are backing up to 3.42s and 3.23s after turbo. Im going to stay with 3.42
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Old Mar 3, 2008 | 07:20 PM
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Yup, I will be going 3.25 with my turbo setup and 4l80e. From what I've ready they will load the turbo allot better too. Like metioned though, its the whole combination................ trans, tires, gears, etc.
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Old Mar 4, 2008 | 09:08 AM
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i would think an m6 car could definately get away with 3.73's, you could always throw a 28" tire on if it just seems to be tacking too high at the end of track. Now if the car were never see the track ,I probably wouldn't even bother with a 3.73 at all.
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Old Mar 4, 2008 | 09:13 AM
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Im not a LS1, but same principle....

I had 3.73's before I went turbo...and up untill early last year. The 3.73's were horrible with the turbo....i swapped out my rear end and put in a ws6 rear with 3.42's and that alone took a full second or more off my 1/4 time....you want nothing taller then 3.42's.
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Old Mar 4, 2008 | 09:20 AM
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I went to 3.50's.
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Old Mar 4, 2008 | 09:25 AM
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thanks guys for all the feedback i went with a 3.50
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Old Mar 4, 2008 | 12:03 PM
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Good choice!

I'm going 3.42 with 28's myself.
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Old Apr 4, 2008 | 11:34 AM
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i have 10 bolt/4.10 6speed. what is the pros/cons? VS. 3.42's?
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Old Apr 4, 2008 | 11:56 AM
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i have heard that the 2.73s for automatic cars work great for turbos, atleast thats what my friend tells me with his turbo camaro
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Old Apr 4, 2008 | 11:56 AM
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Turbo cars loved the smaller gear and make boost quicker with more load. We went with 3.50s for right now and moving to 3.25s once trap speeds get over 190.
Phil
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Old Apr 4, 2008 | 01:05 PM
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my new rear is a 3.0, should help around town quite a bit
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