Planning on buying a Rotrex S/C in a couple of years, but have a question about the best trans/diff combo? I have a 2000 LS with a 5-speed and 4.3 LSD. I bought an NA 4.1 LSD to use with the 5-speed, but have been hearing that if I wanted a 6-speed, that the 4.3 LSD would be better to have, especially if I plan on using a Rotrex later on? Can anyone confirm this?

Thanks!

 

Typically the more power you add, the lower numerically gear you want. Stay with the 5 speed until you need the strength of the 6 speed. 225 ft/lb give or take is the swap point. In my opinion that's also the point in which lower gears like a 3.9 or 3.6 start to make sense. First gear is just a smoke show.

You were very vague in what you are using your car for, better depends on the application.

 

Thanks

I was going to do the swap now, as I'm pulling the engine out next month. I don't do much with my car, just cruising through curvy streets has been my main goal, but this year, it's been parked in the garage for the most part...

 

A friend has a 6-spd/4.3 combo, another enjoyed his 6spd 3.9. It really all depends on how you use it and what you prefer. The 4.3 guy loves autocross, the 3.9 guy did a lot of HPDE, and our local track has 2 big straights. If you love driving, the feel, the engagement, the acceleration, the sounds, have special leather driving gloves, you'll probably love the 6spd/4.3. If it's your DD for your 30 mile freeway commute, maybe even consider a 5spd/3.9.

More than likely however, you're somewhere in between. I'd probably start with the path of least resistance. Use what you've got to start, if you feel like you're running out of gear, get a taller ratio. If it feels sluggish, go shorter.

 

It's not my DD. It might leave the garage once or twice a month, throughout the warmer months. Winter is stays planted in the garage or I'll tinker with it, like now. Engine and trans came out Sunday! I don't auto-x it and there aren't any tracks nearby. It's mainly used for street/curvy mountain road driving. Not worried about being a gas saver. I want something a little quicker from a dead stop and something that has good power from 2th to 4th, inn the hard curvy roads in north Alabama/south Tennessee? I can keep my 5 speed and get a 3.9 or get a 6 speed and 3.9, but the 3.6 is a little outta my price range for a car that never sees more than the street... So, what do yall think I should go with?

 

6sp/3.9 is as short as I would ever go for a Rotrex. If the car had 4.10s, I would expend exactly zero effort changing those.

 

Thanks. It's not a 4.10 at the moment, I just have a 4.10 wanting to go in. It was stock 4.30 with a 5 speed. I may or may not install a Rotrex in a couple of years, that's why I didn't want to pull the trans/diff out again. I was hoping to get it all done in the winter months.