what kind of difference in et can I expect to see going from a 4.11 to a 3.90 with all else being the same? What can I expect to see if the converter is specifically set up for that combo and performance seems really off?

I finally got my new car out a couple of weeks ago, and while I managed to bring home the trophy, I had a ton of issues with the car. The big thing was I was down on et by .5 seconds and mph by nearly 10. I do have a brand new chance converter spec'd specifically for this car, but it seems that it's flashing about 600-700 rpm higher than Marty said it would.

Any insights before my next outing?

it seems your converter is wrong and putting in a gear that will slow you by 3 to 5 is not going fix it.my 02

Changing to that gear ratio will make you converter flash higher.

As for the ET change, I don't worry about that; it's bracket racing! The important thing is you got the win.

2BKING

If you change the rear gear from 4:10 to 3:90 your converter with loosen some, how much who knows? But not in the direction you want

Assume you have a bolt together converter, change the stator

quote:

Originally posted by Big Steve:
If you change the rear gear from 4:10 to 3:90 your converter with loosen some, how much who knows? But not in the direction you want

Assume you have a bolt together converter, change the stator

I do, and once I can get a good data log I'm going to reach out to Marty and see what he says. I've also got a set of 4.11's now, just need to order the carrier and parts so I can swap it out...

Well, made a command decision. The guy buying my old car hasn't contacted me in two months so I pulled the 4.10's out of it and swapped them into the new car. Went to the track this last weekend and no matter what I tried, I couldn't hook the car. Track was just too cold and not sticky enough. But......it is much happier with the 4.10's vs. the 3.90's. So I ordered a new carrier and spool to finish off the new diff so I can put the old one back in the old car.

Now comes the big question. Should I pony up for a set of 4.29's as well? I've got plenty of room for the additional rpm, thinking it might actually be better....thoughts?

I went from 4.10 to 3.90 over the winter. My car slowed down .04 to .05 and lost 2mph. The car is a lot less violent on the starting line now. I think the et loss was worth how the car leaves now. Currently running 4.43@158