So I was talking to John Calvert this last weekend and he was saying to improve my 60' and ET that steeper trans gears would help. Has anyone tried changing the gears on the C4? TCI has a gear set that changes 1st from 2.46 to 2.75 and 2nd from 1.46 to 1.57. I'm wondering if this will help my ET's, especially since I am changing tires from 26" diameter to 27.7". I have a 331, 4.30 rear gears, currently spin the motor to 7300rpm at the finish line at 125mph and have a 5500 stall converter. Or do I just add nitrous and keep the same trans gears ?
erick, i'm running the 4.30 gears in the rear with a 4500 stall convertor. also 26" tall tires. i'd sure like some more off the line too. if anyone should know it would be john calvert. let me know what you find out.
I have changed the gears in my tranny.....but I only have 124 miles on my car and I don't race it....so I really can't help much.
When I did it I didn`t like the shift from second to drive. If you ever drove a 3spd stick you know what I mean 1st is in the basement, second on the first floor and 3rd is in the attic it seems like a big step. But that was my combo it only ran low 13`s at that time and was trying anything to get 12`s. I then put it back to stock and a 125 shot of spray and went 11.76. but that was my car yours may work different. Its funny back then we used a trans out of a 60`s econoline van they had lower gear sets
Sounds like a great idea on paper, but there's more to it. The converter will play a role. If it's too tight, it will bog upon the shift because of the greater difference between 1st & 2nd gear. If it's too loose, it won't help you a bit. Personally, I'd make a pass at the strip & see what it does just like it is....but with the larger tires. Then watch your trap RPM with the bigger tires. If you want more RPM at the stripe, a deeper gear is in order. Less RPM, a higher gear. I would suspect that a deeper gear will help the finish line RPM to stay about where it is, depending on tire growth and converter but it will more than make up for the taller tires on the first 300' of track. You get to a certain point where using a deeper gear just increases your starting line ratio. A stock C4 is 2.46 in low. Add 4.30 (rear gear ratio) and you have a starting line ratio of 6.76. If you go with the 2.75 low, your SLR will increase to 7.05. If you have tire spin or wheelstand problems now...they will be worse with the low gear kit. Thats why sometimes you will see guys that convert to a Powerglide...and won't lose one bit of ET, even though the low gear is only 1.76...BUT the car will become more consistent because it's less likely to spin the tires. Good luck.
