2WD TH400's have speedo gear?

[dremu]

Swapped out the TH400 (ca. 1974) in my tow rig with a newer one, from a diesel, so ca. '85.

The speedo now reads ~25% too fast, and makes a terrible racket at low speed, bounces up and down.

Did it just magically happen that my speedo is on its way out, or is there some difference between these era trannies? I still have the old one, so I can swap parts, but I didn't know they were different. Neither had boxes on the speedo output like I've seen on transfer cases, fwiw.

-- A

 

[JDNobodi]

I'm not 100% sure, but I think you can change speedometer gears in the transmission to change the speed ratio. I have to look into it and by then somebody else would post the right information.

 

[dremu]

I'm not 100% sure, but I think you can change speedometer gears in the transmission to change the speed ratio. I have to look into it and by then somebody else would post the right information.

Well, that would 'splain it. Guess I'll hafta tear into the old tranny, see what's easily removed.

-- A

 

[dremu]

Just occurred to me that OF COURSE they have gears, to account for the rear end ratio ... this truck has a 4.10:1, the donor musta had like a 4.56:1 or something.

-- A

 

[broncoman6524]

Exactly, my speedo does this too...except i went from 3.08s to 3.73s

 

[dremu]

Well, it's stupidly easy to replace; didn't even need to drop the pan as it's above the fluid line.

Just like the 4WD ones for t-cases I'm sure they come in a bazillion sizes; I note that the holders I have are marked "40-41-42-43" and "36-37-38-39." The holder must be switched with the gear, inasmuch as the gears don't fit the other holder.

Anyway, it's one bolt that holds the thing into the side of the tranny, and voila, green one out, orange one in.

-- A

 

[DesertDueler2]

Dont forget to swap the govner as well. the diesel one will make it shift too low.

Dan

 

[dremu]

Dont forget to swap the govner as well. the diesel one will make it shift too low.

Dan

Ya know, I forgot about that...

-- A