If I where to go from 3.42 posi to 3.73 posi what actual gain might I see on the launch? Any comments welcome. I have the chance to get a new GM 3.73's carrier for 45 bucks CDN.

 

I always read that auto's work better with 3.42's but im not 100% sure.

 

Nah 3.73s are alot better, you will see a change in shifts and performance on the track, **** you could get 4.10s if u have overdrive and be safe for road use and kickass on the track, my friends bro just did it to his RS.

SSXeon

 

It will feel quicker, I don't doubt that. But on a stock or near stock RS, 3.73 is way too much gear even for a T5 - 3.42 is borderline. I don't think you will see any improvement in track times. In fact, performance might actually decrease regardless of what the butt dyno tells you. Then there is the issue of traction.

4.10s with a 700R4? He must be crazy. That might work for an underpowered 4 banger or 6 cylinder, but not a V8 - even a worst case scenario. Just too much torque with too much gear.

AndrewC - As long as you have both the RPM and traction to go with the extra gearing, you should be quicker. 3.73 gears are a very common and very good match to the TH350 with many different engine combos. JUST MAKE SURE YOU CAN PUT IT TO THE GROUND!

 

I dunno what the guy has for a tranny but he did it and loves it. He has a 350 in his 3rd gen so whatever. Im thinken of 3.73/4.10s with a 10bolt/12bolt rearend, in the future after i buy the 350HO from my friend at pohanka. Later

SSXeon

 

I have TH350 on a 400 sb .30 over and dual 4's 3.42 in there now , but id like to launch quicker

 

What about a stock '92 Z28 with 350 auto and 3:23 gears ? Would 3:42's do me some good ? What would my speed be @ 70 mph after new gears ?

 

Patriot - I would not advise the switch from 3.23 to 3.42 due to cost. Gears, plus install kit, plus labor usually runs about $500-$600. Thats a lot of money for little gain. Put that money to better use - like an LT1 cam or a StealthRam setup

 

I have 3.73's in mine now. It pulled like crazy and I owned people in the 1/8th but mixed with TPI's upper RPM problems anyway it was a dog after that. Thats why I went to carb but I havent got all the kinks worked out yet so I dont know how much beter it will do. SO if you are running TPI dont bother with the 3.73's

 

I had 3.73s on mine when I switched to 4.10 and hated them. Now I am back to 3.73. I used to get 300 miles a tank cruising and with the 4.10 I get 200. Not that great an acceleration gain with the 383 engine and 700R4 tranny.

 

If this isn't a daily driver and you want good 1/4 mile times, go with 3.73 or 4.10. You can always change tire height to compensate for the gears.
With 4.10's in 3rd gear at 55mph you will be around 3500-4500rpm (I am trying to remember the rpms on my brothers 4.10 6 speed car in 4th gear at 55 and I am drawing a blank and I am too lazy to check the gear/mph/rpm calculators).

 

3.42 will let you keep some top end for the freeway. If you already have them why not spend your money elsewhere just buy a bottle and spray Da Juice!