th400 + 3.73's = what tires size?

[Quickturbosix]

TH400 with a 3.73 rear....What size tire will put me threw the traps at around 5800 rpm? 28? 29?

Or should I get a smaller gear to try and match the stock rear.

Not real sure how close the third gear ratios are in the 400 compared to the 200.

 

[Joe Lubrant]

The 3rd gear ratio of the TH400 & TH200r4 are the same 1 to 1

So if your engine combo has not changed, and the only change was from a 3.42 gear to a 3.73, then a 28in tire should put you back to where you were rpm wise.

Just ballpark figuring here, but if you had a 3.42 with 26" tires and just changed gears to 3.73, you would add approx. 9% more rpm.
Example 5000rpm thru the traps(3.42) would then become say 5450rpm(3.73) with the same size tires.

So basically going to a 3.73 gear & 28" tires would be about the same as 3.42 gear with 26" tire.

Hope this helps?

 

[Quickturbosix]

Thanks Joe. I was thinking on that line but need to hear it from someone else to be sure.

 

[chris718]

THEORETICALLY THIS MAY BE CORRECT BUT WE FORGOT SOMETHING ,IN DIRECT DRIVE ENGINE AND TRANS RATIO IS NOT EQUAL AS SUCH WE SHOULD ADD 200TO 300 RPM TO THE END RESULTS WHEN NOT USING A LOCK UP CONVERTOR ,unless of course it is a neal chance piece .

 

[TurboDiverArt]

Originally posted by Quickturbosix
TH400 with a 3.73 rear....What size tire will put me threw the traps at around 5800 rpm? 28? 29?

Or should I get a smaller gear to try and match the stock rear.

Not real sure how close the third gear ratios are in the 400 compared to the 200.

I think it depends on your combo and how much power you are putting out. I have 3.73's in the stage car and run 29.5" MT's and go through the traps at over 6000 RPM at 140. Really depends on combination and what MPH you are shooting for. If you are shooting for about 125 MPH 28's should probably get you there at 5800 provided it's not a really loose converter.

 

[Quickturbosix]

Shooting for mid 130's @ 10.50 or better.

Combo: lt70, 72's, powerstroke ic and 3" plumbing, Lunati 224 cam, KB 70mm tb and plenum, ATR ported iron heads, ported lower intake, stock ported headers, BGC stainless crossover with Racegate, Trans + with extender, 3.5" maf, AC 9" 4000 stall non lu, th400 with t brake, Mark Williams 3.73 spooled rear, Moroso springs front and rear, drag shocks front and rear, air bags, South Side Machine upper and lowers, 28x10 Hoosier quiktime pros.

Car is about 3700#'s. Going on a diet as soon as weight watchers drops their price.

Stock block car...girdle and caps are in the works now.

Think it can push a 9.99? I think I need better heads to hit the 9's. ATR's flow 212/178.

 

[TurboDiverArt]

Originally posted by Quickturbosix
Shooting for mid 130's @ 10.50 or better.

Combo: lt70, 72's, powerstroke ic and 3" plumbing, Lunati 224 cam, KB 70mm tb and plenum, ATR ported iron heads, ported lower intake, stock ported headers, BGC stainless crossover with Racegate, Trans + with extender, 3.5" maf, AC 9" 4000 stall non lu, th400 with t brake, Mark Williams 3.73 spooled rear, Moroso springs front and rear, drag shocks front and rear, air bags, South Side Machine upper and lowers, 28x10 Hoosier quiktime pros.

Car is about 3700#'s. Going on a diet as soon as weight watchers drops their price.

Stock block car...girdle and caps are in the works now.

Think it can push a 9.99? I think I need better heads to hit the 9's. ATR's flow 212/178.

I think for 9's you should have a girdle, that's a lot of HP for the stock block. 135, I'd say you're going to be a little above 6000 RPM with a non-lockup 4000 stall. Maybe if the converter is real tight you can keep it under 6000 but I think you are going to be over 5800 but who knows.

 

[Joe Lubrant]

Originally posted by TurboDiverArt
I think for 9's you should have a girdle, that's a lot of HP for the stock block. 135, I'd say you're going to be a little above 6000 RPM with a non-lockup 4000 stall. Maybe if the converter is real tight you can keep it under 6000 but I think you are going to be over 5800 but who knows.

I agree with Art, my old combo with PT70- 23-24 PSI Boost, 3700# 10.18@133+, AC 9" 35-3600 stall, 28x10's, & 3.73 ---6250-6300rpm

 

[TurboDiverArt]

Originally posted by Joe Lubrant
I agree with Art, my old combo with PT70- 23-24 PSI Boost, 3700# 10.18@133+, AC 9" 35-3600 stall, 28x10's, & 3.73 ---6250-6300rpm

You mean I was actually right about something? Damn, I gotta keep eating those Wheaties