The 700R4 has a 3.06 first gear and third gear is 1:1. A stock drive shaft is made just strong enough for a stock drive train. When you start spinning one as fast as you are then it starts to distort. This is what causes the vibration. Most of the time a car with overdrive and low rear end gears will require an after market drive shaft that is built to handle higher RPMs.

 

Living here in NC there is a guy in Winston that makes HP driveshafts for alot of race cars and race teams. He also alot of custom shafts for big high hp dragsters. I took him my drive shaft and he is making me a new drive shaft from scratch he garentees NO FLEX at all

 

how about those running the 3.42 gears what does the freeway feel like?? or with 3.73? what the top end?? also with the 4.10 gears what was your top speed and how quick did you get there? i really need to make the right decision because i wont be able to do it twice and i definitly dont want to be dissapointed

 

Damn, that's no surprise at all! 4.10's behind a 700r4 basically is like a dump truck in 1st gear. You're probably aware of this already, but on your overspinning of the driveshaft, switching to an aluminum driveshaft helps considerably. I put a factory aluminum shaft in mine a few years ago and it felt quite a bit smoother at freeway speeds. Even when you get the T5 swapped in your car, you'll probably be happier with 3.73's instead of 4.10's since the T5 has a 2.95 1st gear ratio, so it's not much different from the 700r4. Another thing you can do to help traction is put on a pair of lower control arm relocation brackets. You get more bite when you change the angle of the LCA's. A Spohn adjustable torque arm would be another good idea. Traction always becomes an issue when you replace the anemic factory motor with a stronger one, and put a healthy set of gears out back.

 

Honestly, I wouldn't go any lower than 3.73's. Even 3.42's give you a nice takeoff from a standing start, and 3.73's would provide outstanding takeoff ability while still being liveable on the freeway. If you went with 4.10's, 1st gear would be pretty much useless.

 

alright well, maybe you have convinced me to get 3.73's instead of 4.10's. i just want to get the most out of my car you know.

 

There is almost a night and day difference between the slow motion 2.73 gears and 3.23 gears.

Before, when I ran my car at the track I could play with the radio and adjust the volume and count sheep until the car hit the top of 2nd gear at the end of the quarter mile.

I swapped my open 2.73 rear end for a 3.27 posi borg warner rear end and the takeoff is better, the acceleration is better and it runs good through the gears.

I used to cruise going 70mph at 2000RPM with the 2.73 and now its 70mph at 2500RPM.

3.73 gears would be nice but dont expect your car to be a highway cruiser at a nice low rpm.

In my opinion, the 3.23 gearing is a nice all around gear ratio and the 3.42 is for just a bit more acceleration.

 

i have a quick question... why would somebody wanna put a posi trac in their car.. i thought LSD was what you wanted?? just some simple explanation would be nice.. ive seen how ppl are sometimes lol, they get one stupid question and they freak out so please dont hate on my dumb question!!!

 

Eaton made a limited slip differential and sold it to GM in the '60s. It was installed in may Chevy performance cars. It was called Positive Traction. The name caught on and was shortened to Posi. This name is the trade mark for Eaton's limited slip differential. It became the generic name for all limtied slip differentials, no matter who made it. Ford called theirs a Traction Lock, Dana's was the Power Lock, Chrysler used an Auburn called Sure Grip and there were many more. They all became known as Posi. Posi is limited slip.

 

There is one caveat going from an open differential to a positive traction differential:

Becareful with slick/wet surfaces, especially during the rain.

I have heard a lot of stories of owners who drive posi cars for the first time or do a swap only to wreck the car during wet weather. The posi tries to keep both tires spinning as much as possible, even during a turn.

Flooring it during a turn with an open differential is much different than when you floor it with a posi.

I have seen too many nice third gens with wrecked rear quarter panels because it was slid into a tree.

 

but its so nice to leave this,



peg leg burn out aint near as fun, thats one of my old peg legs to the right of the new burn out

 

Did you ever make this change and how did it work out for you