lockup converter

[marvxyz1]

I have a 1980 GMC, six auto 350 trans. and I don't believe I have a lockup converter on my truck, my question is, would there be any benefit in having one? Obviously, I don't race or anythin. I would only be looking for improved gas mileage. thanks for any possible useful info. on this...marvxyz1

[Slonaker]

The lockup converter allows you to turn a few RPM less at cruising speed. It removes the slippage that is built into automatic transmissions that allows you to stay in gear when stopped. It saves gas rather than being a performance thing.

I have no idea if it was offered in 1980 or on 6 cylinder trucks. You can tell if you have one by looking at the transmission. If it has the lockup torque converter, there will be an extra electrical connector on the transmission. It is square, maybe a little over an inch on each side, and has spots on it for a 4 wire connection, one of which is unused.

I can't remember which side it is on (I haven't looked at mine in years), but it plugs in low on the transmission, and comes straight down into the connector.

Slonaker

[gchemist]

A lockup will save you 200-300 RPMs. That's a lot of RPMs. The lockup is known as poor man's overdrive. So yes, a lock converter will increase MPG.

The plug is on the driverside.

[piecesparts]

The 350s with the lockup converters were listed as 350C trannys. There were a lot of them in the mid eighties, but I don't think they went back to 1980. They are a fairly good tranny, but many were taken out of the trucks and pitched, since the output shaft on them were of a smaller design. If you are going that route, I would look for a later model 700R4 and get the fourth gear Overdrive as well as the lock up and not to mention the lower ratioed first gear.

[D13]

It will help only if you drive hghway a lot. Assuming this is a 1/2 ton w/250, the axle ratio won't let you drive lin lockup below 50mph or so. [I]f you have a 292 you probably can get away with it. But finding one is hard, finding someone to properly rebuild one is harder, and finding a good converter is $$$. You'd be better off swapping in a 200-4R out of a V-8 car. But the key is to remember your cruising RPM needs to be around 1600-2000 or else it'll start bucking under load.

[gchemist]

You don't need an electrical connection for a lockup. Aftermarket torque converters will lock up. I ran the previous 700R4 rebuild and the current rebuild without electrical lockup. The previous convert locked up at 1800 RPMs. I'm not sure so on the current one. The stall is 2500 but I'm almost sure at low cruise speeds the stall is lower.