th350c to 700r4 trans swap help - The 1947 - Present Chevrolet & GMC Truck Message Board Network

crackajacka · 02-02-2004, 06:16 PM

ok ive got an 86 gmc 1/2ton 2 wheel drive truck with a 350 in it(with a edelbrock performer carb on it) and im wanting to swap it out for a 700r4 trans. ill be needing better mpg to get to work and some schooling. what rear end would ya'll recomend for this also. my gf is bout 8 1/2 weeks along so i need to get this done sometime soon plus this one is slippin and engageing late n hard as hell lol. but id like to hear ya'lls opinions, btw mom n dad are helping out with getting the 700r4 level2 from 700r4.com.

thanks

Paul

**swervin ervin** · 02-02-2004, 06:32 PM

I vote for a 3.73 ratio. This is what I have and it works great. I can run down the interstate at 75 and around 2200 rpm. Works for me.

Stepsides 4Ever · 02-13-2004, 04:42 AM

How tall is the rubber on the rear of your truck? I want to crunch some numbers, but I need the diameter of your wheel/tire
combo ...

Thanks!

**swervin ervin** · 02-13-2004, 11:19 AM

27 inches. Let me change my statement a tad.

I said 2200 rpm at 75. Won't compute. With 27 inch tires, 3.73 gears and the .7 OD, it will be more like 2400 rpm at 75 mph. With a 28 inch tire you would be around 2200 rpm at 70.

Then take into consideration of the lockup. This will lower the rpm around 200 rpm or so. This is where I come up with 2200 rpm at 75.

Stepsides 4Ever · 02-13-2004, 01:45 PM

Too cool!

Thanks for the info. Definitely sounds like the 700R4 is the way to go as far as the transmission goes.

What kind of mpg are you getting?

02-02-2004, 06:16 PM	#1
crackajacka Stylin Join Date: Sep 2001 Location: Tuttle, OK Posts: 620	th350c to 700r4 trans swap help ok ive got an 86 gmc 1/2ton 2 wheel drive truck with a 350 in it(with a edelbrock performer carb on it) and im wanting to swap it out for a 700r4 trans. ill be needing better mpg to get to work and some schooling. what rear end would ya'll recomend for this also. my gf is bout 8 1/2 weeks along so i need to get this done sometime soon plus this one is slippin and engageing late n hard as hell lol. but id like to hear ya'lls opinions, btw mom n dad are helping out with getting the 700r4 level2 from 700r4.com. thanks Paul __________________ Ive been traveling for some time, with my fishin pole and my bottle of shyne. Most Girls like finished products and just dont understand what a good addiction does for you http://www.paulwall.us/

02-02-2004, 06:32 PM	#2
swervin ervin You get what you pay for Join Date: Dec 1999 Location: Cherryville, NC Posts: 4,798	I vote for a 3.73 ratio. This is what I have and it works great. I can run down the interstate at 75 and around 2200 rpm. Works for me. __________________ Mike 1985 Chevy C-10

02-13-2004, 04:42 AM	#3
Stepsides 4Ever Stepsides Are Bedder Join Date: Feb 2004 Location: Norco, CA Posts: 238	Hey, Swerve... How tall is the rubber on the rear of your truck? I want to crunch some numbers, but I need the diameter of your wheel/tire combo ... Thanks!

02-13-2004, 11:19 AM	#4
swervin ervin You get what you pay for Join Date: Dec 1999 Location: Cherryville, NC Posts: 4,798	27 inches. Let me change my statement a tad. I said 2200 rpm at 75. Won't compute. With 27 inch tires, 3.73 gears and the .7 OD, it will be more like 2400 rpm at 75 mph. With a 28 inch tire you would be around 2200 rpm at 70. Then take into consideration of the lockup. This will lower the rpm around 200 rpm or so. This is where I come up with 2200 rpm at 75. Last edited by swervin ervin; 02-13-2004 at 11:25 AM.

02-13-2004, 01:45 PM	#5
Stepsides 4Ever Stepsides Are Bedder Join Date: Feb 2004 Location: Norco, CA Posts: 238	Too cool! Thanks for the info. Definitely sounds like the 700R4 is the way to go as far as the transmission goes. What kind of mpg are you getting?



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