The Stovebolt Site Forums The Parking Lot Big Bolts 6500 transmission question

I saw a 1957 6500 truck for sale. It has a 283 and overdrive transmission. Does anyone know if these came with the R-11 overdrive?

Being such a large truck it's not likely a BW overdrive unit like used on the small trucks and cars.

Could be a Clark 5 speed overdrive, or possibly a Spicer. Or could be an auxiliary transmission with overdrive after the usual 4 or 5 speed, If so likely a Spicer 3 speed, possibly 4.

It could be a NP-540 series, 4 shift rails, Al top cover, or Clark, 3 shift rails, Ci topcover with rounded corners.

Both of these trans.' have high(OD) gear to the right and forward, direct is right and back.

Both of these trans.' have a big gap in ratios where they got the OD position from(3rd), which is really awkward with a load unless a two speed rear end is there.

Ed

Good info. Thanks gents.

IF you have a OD transmission, it's not a factory transmission. Chevrolet never put a OD trans in a 1957 big truck (only the 3100 & 3200 had a optional OD transmission). The 6000 Series Trucks were standard with the SM-420 4-speed with an optional New Process 5-speed (direct drive). This 5-speed has a shifting pattern that looks like this;

1...2...4...R
....3...5

Mike B