I have a Moser 12-bolt with 3:73 in it currently.
It's a 92 Camaro,357 C.I.,650DP,approx 3200 w/me,TH350 stalling at 2800-2900, 26" tall tire.
I shift at 5900-6000 rpm and I am crossing the traps at 5300rpm.
I am looking to cross at 5900-6000.
Or would I be better off with 4.56 and a 28" tire?
I have done the online calculators and was looking for anyone that is running or has run a similar combo to guide me in the right direction.
Thanks Mike T

 

I would go with a taller tire first then adjust the gearing accordingly. To get the best performance, you should be crossing the finish line at or slightly after you hit the shift point rpm while in high gear, not OD. Only crossing at 5300, you either need a higher stall converter or deeper gears.

 

Yeah I do need a higher stall,peak torque is at 4400 rpm, but I was trying to make sure I had the optimum gear for my combo first.That and my trans is old and I am saving to do the trans and converter at the same time.
Thanks
Mike T

 

I run 4.86 gears. I shift at 7400 and go through the traps at 7400. A couple of years ago, I tried some 4.57 gears for a few races. Still shifted at 7400 but went through the traps around 7100. ET and MPH never changed but the car felt slow with the 4.57 gears.

The biggest thing I noticed was the amount of converter slip just from the gear swap. With the 4.86 gears, my converter slip calculates to around 4%. With the 4.57 gears, the converter slip was around 13%. The gear change should have also had a stall speed change.

As nice as it would be to say use x.xx gears with xx" tall tires and xxxx stall speed but so many factors affect each car differently, it's more of a trial and error process to find out what works the best.

My car originally started off with 26" tall tires and 3.27 gears. Each tire size increase over the years got a new set of deeper gears and the race converter stall speed was bumped once from 5700 to around 6000. I went from 3.27 to 4.10 to 4.30 to 4.57 to 4.86. I'm almost ready to put in 5.13 but that's a little too much. 5.00 would be a better ratio for me but it's not as common a size. The 5.13/5.14 gears would be nice if I had 33" tall tires but I don't have the extra room. 32" is the tallest I can put under the fenders without doing more surgery at the front and back of the wheel opening.

Put a taller tire on, get a deeper gear, get a converter stall speed to match the camshaft and try it out.

 

I ordered a Jeg's 3100-3500 converter yesterday.They said with my cam it should stall around 3200-3300.
Cam is 500/500 lift 235/245@.05 solid lifter.
I may hit it with a 100-150 shot of nitrous in the future so I think this should be good with a 4:10/28"tire combo.

BTW,how do you calculate converter slip?

Thanks again Mike T