The 1947 - Present Chevrolet & GMC Truck Message Board Network - View Single Post - ‘67 C10 Going from sm-420 to TH350

tim_mc · 03-09-2020, 11:12 PM

Good idea to check the rear gear ratio. The TH350 may be OK depending on the tire size and rear gears and what Crazy is looking to gain. Here's an RPM calculator:
https://spicerparts.com/calculators/...rpm-calculator

For my goals and driving style, I need overdrive. After the 700R4 is installed, I should be cruising at 70 MPH while only pulling just under 2000 RPM. The 700R4 has a lower 1st & 2nd gear than the TH350, so local driving will still be fun.

03-09-2020, 11:12 PM	#11
tim_mc Registered User Join Date: Jan 2019 Location: St Peters, MO Posts: 436	Re: ‘67 C10 Going from sm-420 to TH350 Good idea to check the rear gear ratio. The TH350 may be OK depending on the tire size and rear gears and what Crazy is looking to gain. Here's an RPM calculator: https://spicerparts.com/calculators/...rpm-calculator For my goals and driving style, I need overdrive. After the 700R4 is installed, I should be cruising at 70 MPH while only pulling just under 2000 RPM. The 700R4 has a lower 1st & 2nd gear than the TH350, so local driving will still be fun. __________________ 1967 C20, 350 SBC w/Comp roller cam, 700R4 w/3.42 posi, PS, 4-wheel PDB, Old Air AC & GM Tilt column.