What is everyone running? I am thinking of going from 2.73's to 3.73's. I have a posi rear, 350 TPI, free flow exhaust, headers are on the way, 700R4, stock heads, and free mods.

I am willing to add a cam, and a torque converter. The car will not be a daily driver, but will be driven on the street/track.

Post what gear you have!!

 

in my option 3.73 are to high for stock tires. If you have bigger tires on 3.73 may not be so bad.

 

3.73s will be just fine if you have a cam and high stall converter. Lots of people add them to stock cars and love them. I'm getting them because there is a crossram sitting in my garage waiting to go on my car .

 

In my opion 3.42's are th best all around gear for a street strip car that sees a lot of highway driving. They get you out of the hole good and don't kill off to much top end speed. I like the 3.42's. If its mostly a strip car the 3.73's are good too.

 

I love the 3.73. Would do it again in a heartbeat. Out off all the mods Ive done so far, I could deffinately feel (sotp) this one the most. Of course I went from 2.73, so I better have noticed a difference.. I dont have any track times to see how much they really helped though.
Later Barrett

 

I've been running 373s, have 342s in now, while I change my other rearend over to 410s, eaton & 28 spline moser axles. My engine likes the 373s better in town. I DON'T use this car for highway driving though.

 

ttt

 

I have had both and prefer my 3.73s. As for highway haulin'. A couple months ago, I drove from Utah to the coast of N.C. and back without a complaint. not a better gear for the 700-R4 around in my opinion.


JD

 

I run 3.70. The longest run I make with the car is 120 mi round trip to Atco Raceway. Not bad at all on the highway though.

 

Simplest solution is:

T5/T56=3.42

Th700r4=3.73

 

3:73s are going to be too much with TPI, they stop breathing past 4500 rpms. 3:42s will be the way to go, unless you plan on some future mods to help upper rpm power, don't make the same mistake I did, I switched from 2:73s to 3:73 posi, and didn't gain anything, I totally mismatched my gears to the rest of my setup.

 

I went with 3.42 becauuse i love the 3.45 in my 9 bolt, our new 01 S10 quadcab has 3.73 posi rear(didn't know it was posi 'till i found an open field ) it turns 2100 on the highway and is my mother commuter car.....4.3 Vortec auto, faster then my friends 89 S10 4 banger 5 spd with DEEP gears(well i got the hole shot on him it was only up to 55 mph) I also has 3 other ppl in the car......and the extra 2 doors.....neway it is a nice car....props to GM.

 

NO they won't!! Mark read his post. street/strip, willing to add cam, converter ect. You keep saying 4500 rpm, if you can't get a modded 5.0 or 5.7 to pull 6 grand something is very wrong. Hell my STOCK 5.7 full size blazer will pull 5000 rpm. The 2.8 birds had 342s stock. You saying the 5.0s and 5.7s are less than those? Most people on here are trying to learn HOW to modifiy their cars. Why go thru the exspence of changing gears twice? Now we're NOT talking about long stroke small blocks here. We're talking stock stroke, with mods.

 

My question goes to Iroc 22, how come 3.42's with a T/5-T/56, and 3.73's with the 700r4. I have 3.42's now. I had a 700 r4 to begin with and the 3.42's are great. Now with a T/5 it doesnt rip off the line as hard. I was planning on doing 3.73's because the T/5 could definitely take more gearing??? I would say it depends on application between auto and manual, and what your looking to achieve. If its gonna end up a track car you figure running slicks which may run larger than stock tires and possibly dropping your rear end ratio.

 

I might be mistaken, but I thought the TPI induction unit itself it was holds everything back, I don't know everything sorry, maybe someone can help me out, is it that the TPI unit stops producing power past 4500rpms or is the other things like cam and heads on tpi's that limit the power.

 

I sent my order to summit. I got the 3.73's. I think with the right cam and a little more stall, It should be just right.

I didnt want to go with too high a gear, do more mods and then need a lower gear. Twice the money.

Mark, I did port my plenum, So I hope that will open up the TPI a little. maybe get higher rpm's. I may have to do a little head work later on. You said you are running a crate motor. IT may be your intake/cam choice that is limiting you. Your car should scream with the right setup.

 

You're kidding right?

The T56 has a numerically lower first gear than the 700, and a numerically lower top gear (.5:1)

A T56 really demands 3.73 at a minimum. Are 3.42s driveable? Yes. Are they optimal? Not for anything except maybe gas mileage.

I run 3.90's in mine. Did a few calcs and 4.10's would have been to high. But, a LOT of fourthgen guys run 4.10's with theirs.

And before you say anything about the LS1, the 3.90's are in my 84. I still have the stock 3.42's in my Hawk, I'm not spending money on 10-bolts.

 

To 99Hawk120, i feel the same way because i'm runnin 3.42's now and with an auto they were great, witht my T/5 they kinda suck. I'm lookin to do 3.73's i wanna make sure that will be the way to go also.

 

Not knowing which T5 you have, I can only guess whether 3.73's or 4.10's would be optimal for you. But you can't go wrong with the 3.73's.

If you've got the T5 with a .63 5th gear you probably don't want 4.10's, because it has a 2.98 1st gear (almost the same as a 700R4). I had the 3.89s and the T5 in that combination and it was a little to much. Ironically, if you've got the 0.75 (IIRC) 5th gear you can probably run 4.11's, because the first gear is (I think) 2.75. Of course, 0.75 is not a steep enough overdrive gear to really get good mileage with 4.11's

 

The long runner set-up is what dictates the L98's powerband. I am getting ready to siamese the stock intake base to raise my powerband. From what I understand, that will give me an xtra 500 rpms on the top with stock runners.

The debate here is wether or not 3.73's will work with a stock set-up. Again, I have run both at the track. To my surprise, the 3.73's didn't make any difference on the et or mph! These are good gears for the 700-R4, especially if you plan on modding your set-up. Even without modding the intake assembly for higher rpm breathing, with better traction, ie LCA's, SFC's, and/ or Torque Arm I sure that the 60 ft will improve dramatically. I base this on the terrific launch ability of these gears. Anyone else have toughts or views .

Lates,
JD

 

The car at least needs to make power to at least 5000 rpms with 3:73s, any lower and you're going to be pushed out of your powerband, just make sure you got upper rpm power to work with 3:73s.

 

im running a th-350 with 3.73....damn its fast....i love them...i chirp in to second...3.73 are probally the best for street/strip...

And another thing...my car pulls ALL THE WAY TO 6500rpm...

DABE

 

I'm not sure where you get the idea that you have to have a high RPM screamer to take advantage of shorter gears (well, actually I am, but I don't think you're right).

If you shift the transmission at the right point (or calibrate your automatic to shift properly), it shouldn't matter whether your power band is 3500-6000 or 1500-4500. Unless, of course, you run out of gears before the end of the 1/4. (And of course, I just checked, that will in fact happen with a 26" tire and a 700R4 since the redline speed in 3rd will be 93mph).

If your car makes power to 5000, and you plan on shifting there (and running less than 103mph in the traps) you can use 3.73s. If you plan on slower trap speed, or if your car makes power above 5000, then 3.73s should be perfect.

Hell, if your car pulls to 6000rpm and you plan on trapping at 113 or less, you could even use 4.11s.

I'm not a TPI expert by any stretch of the imagination, but if TPI really quits making power at 4500, then I would NOT use 3.73s. I'm more used to carb motors (or LS1s) that make power higher than that and that shifting around 6000 seems to work good.

 

I guess I should have added to my post ttt. When I run at the track, I will be running the 1/8 mile. I may run the 1/4 just for fun and to get some times.

If I run out of gear in 3rd before the end of the 1/8 I will be suprised.

 

All of the stuff I posted was with respect to the 1/4 mile (which is what I prefer). LS1's are not good 1/8th mile cars, and my 84 is set up for the 1/4. Also I assumed a 26" tire.

If you trap 93mph in the 1/8th, you still wouldn't want 3.73s with a motor that runs out of breath at 4500. 93 is simply 3rd gear, 4500 rpm, 26" tire, 3.73 rear. To go any faster you will have to shift to fourth. If you trap 80mph in the 1/8th, then it's not an issue.

 

..

 

I'm very happy with the 3.73's in my 92 RS.
350 with Compucam 2030,Custom Chip and 5 Speed Trans.
-Rich-