Lost reverse in an automatic '93 b2600i

I've tried changing the filter, pan gasket and adding new atf. Didn't seem to phase it, although it does shift smoother in drive. No reverse whatsoever, just revs as if in neutral. Not totally sure what all the previous owner has done, except for it almost overheating once (I fixed that issue). Were the transmissions in these cooled by the radiator or something? The vacuum modulator does leak a little fluid and the shift linkage is loose, but still engages.

do you have low gear? I believe reverse and 1st are on the same band.

Stupid idea, try adjusting either the transmission position sensor or the shifter linkage. I know that in some autos, the shifter can physically be in the reverse position, but the linkage be a little off causing the transmission to not actually be in reverse.

Also, did you clear the transmission cooler? Torque converter? I'd also try replacing the modulator, since it is leaking.

Thanks for the ideas.

Chaser,

Yeah, I'm almost positive it has the low/reverse band.

emjay,

I took apart the linkage going to the inhibitor, added some rubber bushings that looked to be missing and then began adjusting from the floor of the cab with the adjustment nuts. The best I did was get it to not engage in park, so I quickly adjusted it the hell back, lol. I'm thinking I'll have to go with 100% accurate spec on something like that, but I'm definitely not ruling out that as the issue, especially since the shifter was loose. I'm suspicious that someone worked on it before not knowing what they were doing and threw it out of whack.

Haven't messed with a trans cooler if there is one. I let the old fluid gravity bleed (with the pan back in place) over night when I changed it with new stuff recently. I'd say the torque converter probably still held in some fluid. Agreed on the modulator. No smoke from the tailpipe from the intake yet, but it'd probably only be a matter of time with that starting to go bad.

emjay, one quick last question. Where is the transmission position sensor? I do have a shop manual for a '92 b2600i, but this is a '93. The one for the 92 model showed two different transmissions, one as a 4x4 that is electronically controlled and the other which looks more akin to mine that is hydraulically controlled.

They should be the same gearbox, so they should be in the same location 92-93. There **should** be a lever on the side of the gearbox that you can manually control from under the hood or trunk. I would have a helper remain in the truck with his/her foot ON the brake and go through the gears on the transmission itself, with the shifter DISCONNECTED. It will be easy to do from underneath. Also don't forget to use wheel chocks. At this point, we are just trying to see if you can get it into reverse at all.

Sorry, I don't have any pics of an auto trans to show this to you, but this is a technique I've used before with success.

Thanks for the help. I've heard of that before but never tried it. Seems like a good idea, just need to find some time to get under there and do it. I've been working a lot and fixing my girlfriend's Celica, but I definitely want to get the truck going. When I finally remove the linkage and test I'll post back. Thanks again.

Ok, got under the truck this afternoon and disconnected the linkage, chocked the wheels, had someone sit in the cab and hold the brake while I manually turned the inhibitor switch into each gear. Still got the same response unfortunately when reverse range was engaged. On my phone at the moment, but I have pics of the switch and some solenoids/vacuum modulator I will upload when I get home.

Inhibitor switch




Vacuum modulator.


This truck is pretty dirty underneath, so I've been slowly scraping all of it off of the components.

check the vacuum line, does transmission fluid come out?

emjay,

Ran the truck today after putting in a new air filter (never had one from the previous owner). Then I got underneath after shifting gears back and forth and putting in park and disconnected the vacuum modulator vacuum line while the truck was running. All it did was suck in air, no leaks. I also checked some vacuum lines on the intake side of the engine and found this vacuum port busted at the nipple. Disregard the larger vacuum section, I just put that over it in an attempt to temporarily connect it to the busted port.

It's a line that goes to the charcoal canister. Doubt it has anything to do with the reverse, but I'd still like to fix it.