New Process 5 spd.

[R.Smith]

I have the chance to get a new process 5 spd tranny that's currently attached to a 70's 390. I'm thinking I'll get it and swap it for the c6 in my 70 CS in order to get better mpg. Anybody ever done this and will it help?

[70_F100]

If it's an older tranny, there's a good chance it's an NP540. That's nothing more than a NP435 with 4 synchronized forward gears and a granny gear.

If that's the case, there won't be any overdrive.

I changed my 70 F100 from a C6 to a T19 a while back. I haven't driven it much since the swap, but with what little I've driven it, it seems to have lots more power and possibly a little better gas mileage.

Those C6's take a lot of HP to turn!!!

Hope this helps!!

[averagef250]

The 540 and 435 are pretty much the same darn thing. The guts interchange. The 540 was made in dozens of configurations with some OD versions, but the OD ones were a poor design and broke 30+ years ago.

I like the NP435 over the BW transmissions. No real advantage, just like the way all 435's shift. Their synchro design is pretty cool, kind of a "last forever" sorta design if you treat it right.

[70_F100]

The 540 and 435 are pretty much the same darn thing. The guts interchange. The 540 was made in dozens of configurations with some OD versions, but the OD ones were a poor design and broke 30+ years ago.

I like the NP435 over the BW transmissions. No real advantage, just like the way all 435's shift. Their synchro design is pretty cool, kind of a "last forever" sorta design if you treat it right.

Don't disagree on the 540 and 435 being the same, except that the 540 is a 5-speed. Like you said, a lot of the guts interchange. Worked on many of them when I was with GMC in the early 70's.

As for the BW, I'd definitely choose the NP435 over the T18, but I really like my T19 (also had one in a Scout, years ago). The close ratio with the synchronized 1st gear really works well in my truck.

[averagef250]

I guess I didn't say that very well, but you're right, they are not exactly the same, but 435 guts do fit in a 540 and vise versa.