School me on transmission shift adjustments

[dremu]

I've got two TH400's -- though I imagine the basic idea is common to the rest of 'em -- that I don't like the shifting on. One's waaay too soft, the other I gotta wind up the motor way high (which, it being a diesel, is hard.)

So, I'd like to understand it. The modulator adjusts the stiffness of the shift, and the governor changes at what RPM the shift occurs? Other?

I know about the electric downshift if I bang the pedal to the floor, but I would assume that vacuum would also downshift the thing if I get on the skinny pedal halfway or so, yeah?

-- A

 

[lochenjons]

I'm curious too as my th350 lets the motor rev way high before shifting under WOT. Too much really, like the truck seems faster to be 3/4 on the gas instead of WOT

 

[dyeager535]

Your shift kits are going to be what control how hard it shifts. You've got it right on the modulator/governor, however, an adjustable modulator MIGHT change your shift RPM/MPH. I tried this on my TH400, and I seemed to get about 5MPH extreme spread by changing the modulator adjustment to either extreme of it's adjustment.

 

[4X4HIGH]

I know about the electric downshift if I bang the pedal to the floor, but I would assume that vacuum would also downshift the thing if I get on the skinny pedal halfway or so, yeah?

The only thing that allows a TH400 to downshift is the electric switch.

 

[dyeager535]

I know this was brought up before, but is this for 2-1 as well as the 3-2 shift?

My other question is, how does a TH400 downshift to 1st then without a switch hooked up? (In normal driving, like up to a light) Wondering what condition needs to be met for that to occur as opposed to say a 3-2 downshift under throttle? Is it fluid pressure due to engine speed? Low pressure=downshift?

I drove my 400 around without a switch for the entire time I owned it, and I can certainly vouch for the no 3-2 downshift under throttle.