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Gas Mileage change with the t56

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Old 10-01-2003, 09:37 AM
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Car: 97 200sx se-r, 82 Trans/Am
Engine: 350 bored to 355
Transmission: 700r4
Axle/Gears: 9 bolt 3.45
Gas Mileage change with the t56

I am saving to get my t56 (probably from third gen resource or something) but I am wondering what kind of Gas mileage I should expect to get from it. I will get one with the .50 final gear. Right now I have a 700r4 that runs pretty well, but I should experience a greater gain in fuel economy. I just wonder, how much...

Also, my 9-bolt has 3.45 gears, are those good enough to like the 6-speed. I am told that you really need 3.73's before the acceleration is up to par.

And finally...

when I swap out, I need to get a new speedo setup don't I?

I have the old cable driven, and the t56 has an electric sender, right? So I can finally instal a 145mph guage set up...

okay, thanks.

Last edited by foney_email; 10-01-2003 at 09:40 AM.
Old 10-03-2003, 01:47 AM
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Car: 97 200sx se-r, 82 Trans/Am
Engine: 350 bored to 355
Transmission: 700r4
Axle/Gears: 9 bolt 3.45
any ideas?

I know someone has some imput...
Old 10-03-2003, 01:53 AM
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You will need an electric speedo and a dakota digital decoder box.
Old 10-03-2003, 10:33 PM
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Car: 1992 Camaro RS
Engine: 305 TBI
Transmission: GM T56
Your gas mileage will go up no doubt. As far as the 3.45 w/ 6-speed, I'm in the same dilemna. Someone on here has to have a 6spd w/ 3.45's!

-Rippin
Old 10-05-2003, 12:59 AM
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Car: 1987 Pontiac GTA
Engine: ZZ383 HSR
Transmission: T-56 6-Speed Manual
Axle/Gears: Ford 9", 3.89 TrueTrac Posi
I am not 100% sure on this but if I remember correctly the 94-97 f-bodies came with 3.42 rear or something close stock with the 6-speed. I have 3.23 rear with a 6-speed and getting into 6th gear required faster speeds and off the line my car is a little doggie. Most people suggest going up to a 3.73 rear end just to get a better punch from the 6 speed and still being able to maintain gas mileage with the extra overdrive. Some even go up to 4.10 like I plan on doing this next summer. After calculating the gear ratios (tranny gear multiplied by rear end gear) a 4.10 rear with 1st gear in a 6 speed will get off the line like a 700r4 auto with a 3.73 rear end. However the 4.10's and 2nd gear will be much more powerful through the remaining gears but you stay higher in the rpms in lower gears. So mostly you have to look at what kind of driving you do with your car. You should be fine with 3.45's, but 3.73's are a bit more fun. Best thing I can tell you is do the tranny swap, then drive the car with stock rear end. If you like they way it runs,then leave it......If not upgrade later. Not a necessity right off the bat. Hope this helps.

Any questions about the swap just send me a private message or if you have AOL IM my screen name is DCTRANS. I just did the auto-6speed swap this past summer.
Old 10-05-2003, 01:31 AM
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Car: 97 200sx se-r, 82 Trans/Am
Engine: 350 bored to 355
Transmission: 700r4
Axle/Gears: 9 bolt 3.45
so do you guys think that the $1800 tag is good from third gen resource?

I really want to find a junk yard around here that has one, but I dont think I can find one...

what is a good price from a scrap yard?
Old 10-05-2003, 03:49 AM
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Originally posted by cdartz
You will need an electric speedo and a dakota digital decoder box.
One other way is to keep your stock cable driven speedo and machine your tailshaft housing for the cable drive, I just did one today and the cable or the electric speed sensor will work with it.

Jerry
Attached Thumbnails Gas Mileage change with the t56-mvc-024f.jpg  
Old 10-05-2003, 04:08 AM
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One more picture with a 87-92 electric speed sensor in it.
Attached Thumbnails Gas Mileage change with the t56-mvc-022f.jpg  
Old 10-06-2003, 09:55 AM
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Car: 97 200sx se-r, 82 Trans/Am
Engine: 350 bored to 355
Transmission: 700r4
Axle/Gears: 9 bolt 3.45
with the electric speedo, how do you accomidate for rear gear changes and tire sizes?

I know on an acctual lt1, you can use a reprogrammer, but what about with my set up?

I don't have a computer, it is all old school carbed...
Old 10-06-2003, 08:03 PM
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Originally posted by foney_email
with the electric speedo, how do you accomidate for rear gear changes and tire sizes?

I know on an acctual lt1, you can use a reprogrammer, but what about with my set up?

I don't have a computer, it is all old school carbed...
The simple way to install a T-56 in your 82 (and less money) with a cable driven speedo is to remachine the tailshaft for the old style speedo gears like you have now, or convert you dash over to electric and use a dakota digital decoder box to correct the signal to the dash.

Jerry
Old 10-06-2003, 08:28 PM
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Car: 1991 Z28 Vert
Engine: 383 single plane efi
Transmission: T-56
Axle/Gears: 8.8 with 3.73s
Try to find Momar on this board, he knows too much about what you want to know. He did his in a 84 Trans-Am.
Old 10-07-2003, 08:32 PM
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Car: 91 Z28
Engine: 6.0 LSX Single turbo
Transmission: 4l80E
Axle/Gears: Moser 9" 3.55
Has anyone thought of going with an electronic programable speedometer from auto meter. If its compatable with the trans, i think thats what im going to use when i do the swap because its adjustable for gear changes and tires.
Old 10-07-2003, 08:50 PM
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Originally posted by 82z28man
Has anyone thought of going with an electronic programable speedometer from auto meter. If its compatable with the trans, i think thats what im going to use when i do the swap because its adjustable for gear changes and tires.
Yes that will work on non fuel injected cars, But if you run a ECU you will need the proper signal for the ECU to work.

Jerry
Old 10-08-2003, 02:16 AM
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Car: 240sx
Engine: whatever works
Transmission: 4l80e this year
Axle/Gears: 3.512
The final gear in those trannies is freaking insane.

with a .5:1 you could run 5.11:1 rear gearing and still have better final drive ratio (2.5:1) than a stock TH350 with Stock 2.73 gears.

Hell you can run 4.11:1 (2:1) and still be identical to a 700R4 with 2.73 gears... (1.99:1)


its just freaking nuts.
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