My current car and daily driver is an 85 T/A A4 TPI...

I have a set of 2 series 3.73 gears laying around and seriously thinking of upgrading my stock gears with... Im just looking for a bit more of "seat of the pants" performance out of the car...

Im just wondering, ive been reading around and heard that TPI engines are VERY VERY hard to tune...

Is that true? If so, i was wondering whether or not i could bring my car to a local dyno jet and calibrate my speedo with the newly installed gears?

Another question, is there a gear calculator for 3rd gens out there? Im wondering what RPM would my T/A would idle at at 70MPH with 3.73's


i need all the feedback i can get, thanx!!

 

What gears are in it now? 373's are a little tall if you drive on the highway. You will need to change the driven gear with rear end swap.

 

Here's a calculator you can use to find what the difference in RPM will be:
Speed versus RPM calculator

As far as upgrading a TPI engine- it can be expensive. You can get performance parts specifically meant for TPI engines and you can get good numbers out of them. But a 305 isn't the best engine to be building.

The best thing is with TPI you'll always run high torque numbers. That means you'll have very good throttle response, and lots of power on tap coming out of corners or at the lights.

My 350 runs roughly 260 hp and 390 torque. It'll still lose in a flat out race against my LS1, but it's much easier to drive every day. Gas mileage kinda sucks though, I average about 15 mpg. I'm hoping that'll improve once I get it on a dyno.

Here's the parts I used/intend to use on my engine, if you're interested.

Edelbrock.com - Manifolds - Chevrolet - Peformer - TPI
Edelbrock.com - Cylinder Heads - Chevy - Small Block - Performer Corvette (1986-1991)
COMP Cams: Xtreme Energy™, XR258HR <br> Strong Torque, Good Mileage

And I haven't done much research into exhaust yet, so there's that also.

 

I dont know about the tuning issue as my car is carbed....but swapping to 3.73's will cause instant jaw dropping "why didnt I do this sooner' reactions. No single performance mod adds 'seat of the pants kick' like a gear swap. Its not without a downside.....you will loose top end, you will spin higher RPM's on the highway (engine wear, MPG, cooling issues) and the install needs to be done correctly (read expensive) or you will blow up your rear end.

Do it.

 

if you have 2.73 gears currently, the 3.73's will pick up highway rpm by about 700 rpm. the tpi is easy to tune, not so easy to work on and definatly not cheap to upgrade. i have as much into my intake setup and fuel system as i have into my motor