TH350 to 700r4 conversion
 

Can someone point me in the right direction of the post or thread that tells what is needed to change from a TH350 to a 700r4 with overdrive? I cant seem to find anything.
I have a 65 Suburban 1/2 ton 2wd that will be getting a 350 this year. Currently have 3:73 rear gears but need new of those as well
Thank You

Re: TH350 to 700r4 conversion
 

Not sure of the entire "needs list" for doing a swap like that. But under the tranny FAQ section. There is a post by 1bad62 here that has a lot of good transmission info. Hope it helps

http://67-72chevytrucks.com/vboard/s...d.php?t=390542

Re: TH350 to 700r4 conversion
 

Thank you

Re: TH350 to 700r4 conversion
 

No prob man! Love your burb!

Re: TH350 to 700r4 conversion
 

There are tons of posts in the Engine and Drivetrain section all about correctly setting up the TV cable and adjusting the line pressures. As for the actual install, it is basically just moving the trans crossmember back and having the driveshaft shortened. You can either use your existing shifter or change that to your liking.

Re: TH350 to 700r4 conversion
 

Thanks. Lot of memories with the old girl from when my dad bought it in 1976 up until now.

Re: TH350 to 700r4 conversion
 

Thanks Captain. Im going to start looking ibto this swap. What gesrs would you recommend for daily driving? And could I keep them after the swap?

Re: TH350 to 700r4 conversion
 

I have a 350 and a 700R4 in my 66 with a 373 gear. Not a bad combo. I drive it every day. If I did more long interstate runs I would put a 342 in it and still might. Running 65 it turns right about 2000 rpm. I have a 342 to go in my burb and I think it will be a good combo. That one is getting a 5.3 4L60 combo.
Jimmy

Re: TH350 to 700r4 conversion
 

3:73 and a 28"-29" tall tire is perfect. You don't want to lug the engine and ideal RPM's are in the 2100-2300 range at whatever your normal max cruise speed is. If you have EFI, you can lower the RPM range a couple hundred but on a carb, you might find worse mileage.

My old '68 C10 had 4:10's, 28" tall tires and cruising at 70 MPH, I could get 21 MPG. Downside was due to the deep first gear and the 4:10's, I would smoke the tires if I got on it too hard. :)

Re: TH350 to 700r4 conversion
 

Like smoking the tires when you dump the gas pedal is EVER a bad thing?? ;)

Re: TH350 to 700r4 conversion
 

Thanks Jimmy. Right now with a TH350 and a 283 Im turning 4000-4500 rpm at 70-75mph. Waaay to high. I will see how the 3:73's do after I get everything in and set. Id like to take it on long runs but cant ubtil I get the rpm and mileage issues fixed

Re: TH350 to 700r4 conversion
 

First thing you need is a good tach. You would have to have a 4.56 gear with a 28" to turn 4000 at 70 mph. With a 4.11 you would be at 3500 and about 3200 with a 3.73.
Jimmy

Re: TH350 to 700r4 conversion
 

This \/ \/ \/

Since a 283 is low on torque, I would go with 3.73 gears and the 700R4. You could go right to 3.42's if you plan on a lot of highway driving and do not plan on towing anything.

Re: TH350 to 700r4 conversion
 

I have a 66 c10 with a 350 motor and a 350 trans. I think i have 373 gears. When i am going 60 my motor screaming. I was told i need 308 gears.

Re: TH350 to 700r4 conversion
 

This calculator is great to figure what gearing you need with your tire size.
http://www.csgnetwork.com/multirpmcalc.html

Re: TH350 to 700r4 conversion
 

When you say 28"-29" tall tires, are you measuring from the ground to the top of the tire? Currently Im running 235/75r15's but will be dropping to I think a 225/75r15 which is the equivelant of the original 7.15-15

Re: TH350 to 700r4 conversion
 

yes.

Re: TH350 to 700r4 conversion
 

Thanks