1984 C20 6.2 trans question

[5akman]

My 20 yr old son just bought a 1984 C20 with the 6.2l/Th400/4.10/Eaton posi. He's going to be using it for work a day or so a week and has a 150 mile round trip. We've talked about putting a 700r4 in it to help improve the mileage ( I know in a gasser it can drop cruise rpm by 800 or so). Is a gasser 700r4 going to work in this truck or are the diesel rigs different?

 

[1987 GMC Jimmy]

Well, it’ll bolt up, but it doesn’t have a way to engage the TC lockup so you’d have to run a toggle switch and lock it up manually. I’m not a diesel guy, but you’d need vacuum to operate the factory style lockup circuit, which diesels have very little of if any. I don’t know if they had something figured out for that or what the deal is. @Blue Ox

That rear end gearing is going to hurt on those long drives. Something more conservative would need to go in along with the transmission for it all to be worth your while. Just the transmission won’t make more than a slight gain in fuel economy.

 

[82Diesel]

The only thing I know is different is that the 6.2 700r4s have a diesel governor & tv cable? something like that, make sure the TV cable is adjusted properly or you'll blow up that trans like nothing.

P.s 4WD trans will not work in a 2wd truck that runs 2-Piece drive shafts... or you will have to change out the yoke to 2wd.

Vice Versa on the trans.

 

[Blue Ox]

The diesel uses a different torque converter and governor in the transmission. There may be valving differences too, but that's above my pay grade. The TV cable is critical on any 700R4.

@1987 GMC Jimmy , most automotive diesels have an engine driven vacuum pump. On these trucks it's enough for the HVAC and modulator, but not a brake booster which is why these trucks have hydroboost. My VW, OTOH has a vacuum booster. Juice brakes are probably a bit much for a car.

I had a 700R4 in a suburban with a 6.2 and it is better than having the engine screaming at 65 MPH. We ended up putting a Gear Vendors in the pickup with the THM400 and 4.10s. In a perfect world that worked better than the 700, but either is viable.

 

[Rickf]

If the th400 is in good shape, a gear vendors od will be the easiest way to improve mileage. They can be pricey but not too difficult to install and only need to have the driveshaft shortened.

 

[marks86]

The 6.2 has a vacuum pump where a 350 has the distributor. They made plenty of 6.2 700r trucks just find all the tv brackets and you should be good to go

 

[82Diesel]

The diesel uses a different torque converter and governor in the transmission. There may be valving differences too, but that's above my pay grade. The TV cable is critical on any 700R4.

@1987 GMC Jimmy , most automotive diesels have an engine driven vacuum pump. On these trucks it's enough for the HVAC and modulator, but not a brake booster which is why these trucks have hydroboost. My VW, OTOH has a vacuum booster. Juice brakes are probably a bit much for a car.

I had a 700R4 in a suburban with a 6.2 and it is better than having the engine screaming at 65 MPH. We ended up putting a Gear Vendors in the pickup with the THM400 and 4.10s. In a perfect world that worked better than the 700, but either is viable.

Ah Yes Tq Converter I forgot about that. Haha Long night.

 

[HotRodPC]

Governor has different springs and the torque converter is different. Get 6.2 Gov and Converter, should work fine.