The 1947 - Present Chevrolet & GMC Truck Message Board Network - View Single Post - 1978 full-time 4x4. Is a 700r4 worth it?

Jankovic · 02-23-2014, 11:00 PM

Hello All,

I have a:
1978 Chevy
Full-time 4WD NP203
Engine 350 sb Q-Jet
th400
Front axle GM Corporate 10 bolt
Rear axle is a 14 bolt 4.10 gears
35" tires

I want to make any cost-effective changes I can for fuel mileage and DON'T want tbi or part-time 4WD. This points me to a 700r4 transmission. Problem is, based on my calculations I could get good cruising RPMs (60mph @ 2200) from 3.73 gears in my th400. This is a project truck and not drive-able yet, so I have no idea what the MPG is currently. I would be totally happy with 12-15MPG.

What would be the preferred transmission and gears?
Thanks.

02-23-2014, 11:00 PM	#1
Jankovic Registered User Join Date: Feb 2014 Location: Ontario Posts: 11	1978 full-time 4x4. Is a 700r4 worth it? Hello All, I have a: 1978 Chevy Full-time 4WD NP203 Engine 350 sb Q-Jet th400 Front axle GM Corporate 10 bolt Rear axle is a 14 bolt 4.10 gears 35" tires I want to make any cost-effective changes I can for fuel mileage and DON'T want tbi or part-time 4WD. This points me to a 700r4 transmission. Problem is, based on my calculations I could get good cruising RPMs (60mph @ 2200) from 3.73 gears in my th400. This is a project truck and not drive-able yet, so I have no idea what the MPG is currently. I would be totally happy with 12-15MPG. What would be the preferred transmission and gears? Thanks.