what rpm are you guys at? im trying to decide between transmissions, my choices are the th350, simple and easy, or the 700r4/4l60e, more work required via transmission crossmember, custom drive shaft, and harness for the 4l60e.

also with that rpm what gears you guys use and how do you liek them. thanks!!

 

With 3.42:1 gears, I'm at 2654.2 rpm at 60mph. At 65, I'd be at 2875.4.

 

93Formula, what gears are you running and what size tires do you have?

 

honestly im not sure what gears it has, i only drove it for a summers worth, it has a bent axle i think cause one side wobbles, even when we swaped tires. i have spare axles but i may just rebuild the thing with whatever gears are needed. what woudl one suggest?

as for tires well i can use whatever as the old ones are a mix and match set of fiteens. im planning on some TT2s, perhaps 16s?

erik, thats a little high for my liking to be reving while on the highway maybe i should look into a 700r4 or trying to get the 4l60e to work.

what do you think it will be reving with say 2.73s or 3.23s?

 

Use the f-body.org gear calculator. Unfortunately it doesn't have a car with a TH350 in the list, but you can plug in your own #'s.

All that is really important is 3rd gear, which is 1:1, so put in either your tire size or diameter (ie: 275/60/15 or 28") then the axle ratio (ie: 3.42), pick a redline (ie: 6000) and enter 1 in the box for 3rd gear..........now hit calculate.

You can see that with that combo, 60 mph is somewhere around ~2500 rpms. Now if you put in 2.73's, that would bring 60 mph down to around ~2000 rpm, which isn't so bad.

 

yeah the 2.73s doesnt seem too bad, how would first and second gear feel? sluggish?

 

First gear ratio of the th350 is 2.52:1 so yes it will feel sluggish. The 700r4 has a 3.06:1 first. In order to get the same feel as the 700r4 with the th350 you will need around a 3.3:1 gear. I'd go with a 3.23 gear(if the yhave it for that 10 bolt) and a 2200 stall for good performance and freeway cruising.

 

Hey, just for what it's worth, I used to have 2.56's --- yes, 2.56's --- in my '81 Z28!!!! I'm not bs-ing. The ring gear had 41 teeth, the pinion had 16 (do the math....... 41/16 = 2.56, same as 41/15 = 2.73).

.........anyway, my point is, with a strong enough motor, you can still get some acceleration, but on the highway, even driving in 3rd gear is like having over-drive! What was cool about my '81 is that with the 383 it had, it had lots of torque to pull out of the hole, and 1st gear alone would scream out over 70 mph! Then 2nd would bury the speedo, and 3rd gear...................well, according to that chart the car could have done ~200 mph at the top of 3rd!!!!

Not saying that 2.56's should be your #1 choice, but just food for thought --- 2.73's aren't all THAT bad.

 

well my choices are th350 with 2.73s or a 4l60e with 3.23s/3.42s

i was thinking of running a lt4 hotcam or a cc305 with the lt1.

the th350 would still be the easiest for me, no messing with cross member and driveshaft.

the 4l60e ill have to mess with the cross member, drive shaftand wiring. but i have this in my garage and the th350 ill have to buy. decisions decisions.

 

capn pete, how much torque did you have with your 383? or woudl i be able to take care of the lack of torque with a torque convertor?

zedzag, does that mean it will rev around 2200 at 60mph? sorry im an idiot when it comes to autos.

its gonna see highway duty about once a week or so.

 

Hard to explain how the torque converter works but at light throttle it would be less than 2200. When you accelerate hard it'll rev to 2200 then pull from there. I have a 3000 stall but I can start from a light with light throttle and it may only rev to 1500 or 2000 or anywhere up to 3000 but it depends on the torque output of the engine. At cruising speed and light throttle the rpm can be lower than 3000 but with my 4.10 when I hit 90 km/h the rpm would be 3000 anyways so converter won't stall any higher when I add more throttle. With a 3.23 gear and a 2200 stall it would be alot more driveable. I hope you get some of that...you should drive a car with a larger than stock converter to see what I mean.

 

yeah unfortunaltey everyone i know has a m6, maybe ill discuss this with bunker as he had a auto on his 93. im just finding a hard time trying to decide between the simplicity of the th350 or just go ahead with the 4l60e.

 

I can't say for "dyno" sure, but comparing to any magazine build-up, knowing what I ran at the track, and knowing what parts I had in the motor, I'd say the engine was making roughly ~350 HP (crank), maybe ~375 HP, but torque was guaranteed over 400 ft*lbs..............probably in the ~425 ft*lb neighborhood. Trust me, while I realize I'm somewhat "guessing", the car ran 14.2 @ 97 mph, while shifting 1st and 2nd gear at about ~4000 RPM because of a major fuel / ignition problem, yet the car was capable of pulling ~6500 rpm normally (just not at the track! ).

..........anyway, the torque really made up for things even with 2.56's, but I eventually changed them for 3.42's (with a TH350) and WOW.........she moved then!!!

In terms of torque converters and how they work, think of this. A stock TC stalls to usually 1600 - 1800 rpm. This doesn't mean the car won't begin to move sooner, but if you held the brakes and revved up the gas, by ~1800 rpm, the back tires would begin to break free and start spinning no matter what. When you start talking about 2500, 3000, 3500+ stall converters, this means that the converter is able to stall (or "slip") until its rated speed before it will lock up and really start moving the car. Now, unless you are mashing the gas to the floor, they will still work like normal --- let your foot off the gas, drive "normal", and you won't really notice any difference. However, it's just when you start going WOT that you notice the engine rev up higher before the converter grabs, and the whole point is to allow the engine to get up into its power band before the TC locks, so that you don't notice that typical "bog" off the line.

Hope that helps you out a little more?

 

TH350 + 60mph = 1900rpm

 

capn pete, thanks for the explanation.

OP, 1900rpm? what gearing?