How Streetable is a TH350?

[YGspider]

Okay guys I'm almost into the 350/383 build for my Cutlass and its time for Tranmission talks. I have a guy that can build me a really good Turbo 350 for really cheap with a shift kit and a full rebuild and from a guy that has tons of trans rebuilds. Im going for a 383 with 430 HP 500 ft-lb of torque .. The 200r4 is not fully out of the question but with the turbo 350 what rearend gears would I need to run for the car to be decent on the highway and of the line aswell?

I dont want a highway screamer

 

[olds307 and 403]

3.23 is the highest you would want with a 3spd trans with any amount of highway driving. With the 2004r, 3.73 would be no problem.

 

[DRIVEN]

I concur.

 

[Dennyboy]

i run 342 with my th350 and my big block. gas mileage sucks but the engine doesn't mind the rpms

 

[307 Regal]

Well, the TH350 itself is a fine transmission. It all comes down to your rear gear ratio and what RPM your torque converter engages at. My brother's old car (now my dad's toy) has a TH350 in it behind a H.O. 305 and I believe the 12 bolt has 3.73s. I've been inside and behind the wheel of it numerous times. It was liveable on the highway if I remember correctly and on slower streets (~40-45mph limit) I was totally fine with it. Just remember that you are not going to get very good mileage. If you drive the car a lot, having an overdrive might actually save you money in the long run. Also, the trans has a B&M shift kit. It's a lot more (let's just say) "firm" than my transgo kit in my 200-4R, but if you're into shift kits then you can probably live with it.
What's way too much gear for the highway are 4.11 gears. A friend of mine bought a heap of a '70 Monte Carlo with a 327/TH350 combo and 4.11:1 rear gear ratio. It didn't have a tachometer, but I didn't need one to know the engine was screaming on the highway. Actually, "screaming its head off" is more accurate if you include the part where my friend didn't know he was doing 55 in 2nd gear. :lol:
I'd say maybe use a gear between 3.08 and 3.42??
Hopefully someone else can weigh in on a good torque converter to use. You don't want the stall too high for driving in town.

 

[YGspider]

Thanks for the Input so far guys. I'm looking into the 3.08 alittel more. If I can find the 200r4 builder in my area that would be a far better choice in terms of gas milage. To be honest if the car gets about 17mpg with the TH350 id be fine with it. but I want a car that can still kinda getup and go on the highway.

 

[81cutlass]

Very streetable. People drove non OD trans cars until the mid 80's. Millions of cars came off the factory line with 3.50+ gears and non OD transmissions. Only thing different is 75MPH cruises. If you manage to stay off the interstate it wouldnt be too bad. OD makes it 100% liveable at 70+

That being said, I put 3.42's in my cutlass this winter and am putting a 2004R in as soon as the time and parts show up.

 

[Evan11]

I agree, TH-350's are great & dependable transmissions that you can just drop in & with just normal maintance, never really have to worry about it. Another plus is they're a direct swap from the crappy TH-200 & are cheap! I've always heard that 2.73-3.08 gears are the perfect combination for a TH-350 on the street. I run a TH-350 in mine, it now has 2.41 or 2.14 gears. I'm putting in a complete posi rear out of a elky with 2.73 gears this summer. If I like the 2.73's ok, I've got a set of GM 3.08 gears for 7.5/7.725 that I might sell at that time.

 

[DRIVEN]

Thanks for the Input so far guys. I'm looking into the 3.08 alittel more. If I can find the 200r4 builder in my area that would be a far better choice in terms of gas milage. To be honest if the car gets about 17mpg with the TH350 id be fine with it. but I want a car that can still kinda getup and go on the highway.

I think 3.08s are a good choice for a torquey 383. I'd be surprised if you get 17mpg though. Maybe.
The TH350 is a great unit but it is a compromise since there's no overdrive. You'll have to give up some cruise RPMs or some acceleration...or some of both.

 

[pontiacgp]

if you're looking for a good 200 4r to start with I know of a GN 200 4r that's for sale