Derek Edgar

1993 D350, think it has the 518A. Is this a 3 speed? Has O/D button, overdrive? If it has OD, I don't think it's shifting into OD. Just picked this truck up about a month ago. Trying to get some links out of it.
Thanks

AlpineRAM

Hi Derek,

I think this should go into 1st gen.

If it has a button- does it say OD or O/D or does it say OD off or O/D off?

I do not know the first gens, so I can't really help..

Derek Edgar

Thought I was in 1st gen.
Has a button with O/D OFF.

eljefedavies

Go into the stickies and look up Crank sensors and Throttle position sensors (TPS). Common problem with these trucks and a very easy fix. Usually!

Derek Edgar

Both are brand new.
Stickies?

oliver foster

Brand new does not guarantee they are good.... or installed properly.

The sticky is the list of posts that are particularly helpful at the top of the list page of this 1st gen forum.

NJTman

If the OD light isn't on, then in theory, you should have 4th gear engaging when you hit 35 mph or so. It's an electronically activated 4th gear.

There are several ways to determine if you have an electrical issue, or if it's mechanical. I just went through all of this, followed Angry Johnny's advice, and tested the circuit at the transmission, bypassed the circuit, and the transmission still never shifted into 4th. I even tried replacing the 4th gear solenoid in the pan, to no avail.

There was an internal breakage in my transmission. Maybe you'll get lucky and it will simply be an electrical connection or lead.

Angry Johnny

You need to determine if it's working or not first. The shift into overdrive can be pretty seamless in that you may not really feel it but you should hear a change in engine RPM. How many times does it shift? 1st to 2nd is one shift, 2nd to 3rd is the second shift and 3rd to 4th is is the third shift.

cougar

You need to find a place where you can hold the throttle at least half way down. That will spread out the shift points and make them easier to detect.

NJTman

If you dont have 4th,gear, at 65mph, your engine rpms will be over 2000. When my 4th didn't function, going over 55 was annoying, as the engine sweet spot has passed, and the noise was noticeable .

I hated not having 4th

KRB

Ditto that. When I hit 4th at a steady throttle it drops around 150 rpm.