Higher HP cars with TH400

[karolko]

Although this is a transmission question, I was wondering what most of you guys running higher hp setups and TH400's are using for a first gear ratio.

My old 109 setup was already too much for the stock first gear, but I don't know what ratio would be the best for our setups.

271ci 153 Stage II Precision 7576 with th400, 28" tires with ford 9" and 3.50 gears.

Thanks guys

 

[karolko]

l guess my winded question can be summed up to this:

2.48, 2.10 or 1.95 first gears?

Adrian

 

[turbobitt]

The stock gear ratios are fine and with a 28" tire and 3.50 gears is a good starting point.

Allan G.

 

[norbs]

The stock gear ratios are fine and with a 28" tire and 3.50 gears is a good starting point.

Allan G.

Allan do you think you have too much gear?

 

[turbobitt]

Allan do you think you have too much gear?

For my application no, I'm crossing at 6800 and when I turn it up and get it optimized I want to be at 7400-7600 with the same gear.
AG


Posted from the TurboBuick.Com mobile app

 

[norbs]

What would be your estimated MPH your targeting?

 

[turbobitt]

What would be your estimated MPH your targeting?

166-170 mph. Obviously a very stretch goal. But point being that the more power I make, the higher the RPM will be with the same gear and appears to be optimized for my tire size.
AG.

 

[Mike E]

Although this is a transmission question, I was wondering what most of you guys running higher hp setups and TH400's are using for a first gear ratio.

My old 109 setup was already too much for the stock first gear, but I don't know what ratio would be the best for our setups.

271ci 153 Stage II Precision 7576 with th400, 28" tires with ford 9" and 3.50 gears.

Thanks guys

I doubt your going to get anybody to give up this info. At the power level that turbo can make, it's in the edge of benefiting from a 2.10 first gear. I was building a spare trans with a TCI 2.10 gearset, but returned the gearset due to various issues. I'm going to start with the stock set and try a quality 2.10 gear set if it looks like I can benefit from it. Like if I end up having to pull a lot of power to make the car leave or if it's too violent off the line.

The lower first gear of a 2.10 gear set will make getting the correct converter more critical.

A 1.95 set is more for a nitrous promod that makes tremendous torque at the hit. I would try a 1.80 glide before I would try a 1.95 th400.

 

[steve hughes]

I switched to a 2.10 gear set when i was running TSM in 2007 or 2008. It picked up tenth and a half. You will have to turn the 2 step up a little. At the same limit on the 2 step as thr 2.48 gear set it slowed down a tenth. Turned it up 150 rpm and picked up a tenth and a half over previous best.

 

[karolko]

Correct me if I am wrong, but I am under the impression that a 2.10 first gear will MPH higher than a 2.48 first. With my old 109 motor I had a Precision 70mm and I launched at 3600rpm, and the 1-2 change seemed to happen soo fast. I guess the question is " Did it happen too fast"?

Steve Hughes, with your TSM car, you said you picked up 0.15 seconds going to a 2.10 gearset and you only had to bring up the 2 step 150 rpm. What psi were you launching at and how much MPH did you pick up with the 2.10 gearset.

Mike, How hard Is it to change the gearsets? How much of the trans needs to be disassembeled in order to get to the gearset? I am going to have the trans built by Hutch but don't want to have to ship it back and forth to have gearsets changed if I know I can do it myself. That and I don't want to spend that much money if it won't help. Gearsets are not cheap.


Adrian

 

[Mike E]

Yes, you will make the 1-2 shift at a higher mph.

To install the gearset, the trans has to be torn down completely. It's the very last thing that comes out of the case. Hutch has two options on 2.10 gear sets. One is about $1500 and the other is a little over $2000.

 

[karolko]

so the question will remain will it get me there faster.

1500-2000 is an expensive upgrade.

I currently have one of Hutch's TH400 with a stock gearset. I wonder if I spend some time getting hard data, would it be enough to decide if going to the 2.10 gearset will be of benefit to me.

 

[steve hughes]

I was launching with 24 psi. It picked up 1.5 mph. Rpm in high gear is not going to be an higher because of the gear set. High gear is still going to be 1 to 1. Tci makes a 210 gear set to. I think Cal Hartline is a tic dealer

 

[Dusty Bradford]

The benefit of the 2.10 is two fold. The extra wheel speed after launch accelerates the car quicker and you have less rpm drop on the gear change so the engine stays closer to its power band. The less rpm drop comes from the ratio of 1st and 2nd being closer.

The downside is you do have to launch at higher rpm and boost to get equal 60 foot and you do have to have enough power to pull that much gear. A car in the 8s has enough power, 9's is questionable but has shown benefit on cars in the low 9's.


Posted from the TurboBuick.Com mobile app

 

[karolko]

Dusty, you bring up a good point, closer ratio gears will help keep you in the powerband a little better.

I know the car is 8 second capable, but I also know It will be a while until I get all the kinks worked out of it.

How much more boost and how much more rpm are we talking about? I am curious with guys running 76mm turbo, how much boost everyone launches at to get a 8 second pass?

 

[forcefed3.8's]

I launched on 5psi 1.32 60'. I have a PTC 18 blade. Shifting at 7000rpm, drops to 5950 on shifts.

 

[karolko]

I launched on 5psi 1.32 60'. I have a PTC 18 blade. Shifting at 7000rpm, drops to 5950 on shifts.

Forcefed, was that with a 2.1 gearset?

Also what does you car weigh?

Adrian

 

[forcefed3.8's]

2.48 gear. Car weighs 3470.

 

[norbs]

For the price of the gear set you could buy a 4.10 gear and a GV overdrive and launch in 2nd gear for the track, and still cruise with a 3.19 equivalent gear on in OD I think they are close to 2k not worth the .1 to me....

 

[2QUICK2B6]

looking an taking notes ...