Auto OD issues

[RSchwarzli]

Hey guys

I have a Ontario member that is having issues with his rebuilt auto transmission. I recall there being issues like this before woth the early OD trucks but I cannot recall what the solution was. Never played with autos too much. Normally swap to a stick at that point. Lol

Anyways, Steve stated the following:

91 w250 4 wheel drive: it wont go into overdrive. Was in transmission shop for 5 weeks, got a rebuilt transmission, rebuilt o/d section, and still nothing. Any ideas? They figure its something simple they are missing. Also got brand new TPS and wire.



Thoughts guys?

Thanks!

Robert

 

[TAchterberg]

I've read that a faulty brake light switch will prevent OD engagement as well.

 

[DVolk]

Id take it back to the transmission shop and tell them to fix it and if they dont call the bank and have payment reversed/ stopped .

 

[mweiman]

Isn't overdrive engagement controlled by the pcm and crankshaft position sensor? I guess if a/c and alternator are working(if still the factory wiring) that would tell you the pcm is getting crankshaft signal.

 

[PMould]

I have a 91.5 w250.speedo sender drive pin was slipping,no od.no speedo I drove a toothpick in the gap,been working about 4 years.:-laf someday I might need another toothpick. pete.

 

[Philip]

Robert have the owner check the two wire plug at the trans for 12 volt power. If it has power to the plug. Hook a wire to the other wire on that plug. Take that wire to a switch. From that toggle switch go to a good known ground. Test drive the truck. When you flip the toggle switch it should go into OD. If it doesn't tell the trans shop to repair the trans they didn't fix properly.

If it does go into OD then that gives an idea where to start checking.

 

[Andy314]

Hey guys

I have a Ontario member that is having issues with his rebuilt auto transmission. I recall there being issues like this before woth the early OD trucks but I cannot recall what the solution was. Never played with autos too much. Normally swap to a stick at that point. Lol

Anyways, Steve stated the following:

91 w250 4 wheel drive: it wont go into overdrive. Was in transmission shop for 5 weeks, got a rebuilt transmission, rebuilt o/d section, and still nothing. Any ideas? They figure its something simple they are missing. Also got brand new TPS and wire.



Thoughts guys?

Thanks!

Robert

If you are looking for something simple that gets over looked? Try the kick down cable~! My Dads 92 D350 was in and out of the shop multiple times, then when I got it I trouble shot it for almost a year. Finally put on a new kick down cable, it's as good as new.

Andy

 

[DVolk]

really it should be the transmission shops problem but i agre a mis adjust kick down will cause havoc

 

[Andy314]

really it should be the transmission shops problem but i agre a mis adjust kick down will cause havoc

Yes they should have caught this, but if you go to a shop that isn't familiar with these first gens.. Well you know, and I've owned one of every model year from 1885-1992.. But my Dad's D350 was the first diesel I had the pleasure of playing with! The kick down cable set up is drastically different! So I would not be surprised if it was over looked!

 

[Andy314]

OOPS! Should have prove read better That 1985-1992!!

 

[Waynes]

Check the electical

The O/D requires several switches to be made before it will upshift. Not sure if I'll get them all but: Switch on the dash for turning it off, temp switch for when the engine is too cold, temp switch for transmission too hot (I think, can't quite remember), and the TPS. And the computer has to work (and speed sensor feed to computer).

There is a two wire plug, one wire is hot any time the key is on, the other is grounded through the above switches before the transmission will shift up. As my computer partially fried a few months back, I added a wire to the Non Hot wire, going to a switch, with the other wire to the switch going to ground. Once you get to third gear, select the switch, and it will upshift in about 3-4 seconds. My switch is lit, but I still forget to turn it off. The transmission will downshift once you stop, but pretty much goes to O/D from when shifting to 3rd. If you just slow down, acceleration will be slugish.

Wayne

PS - I tried a '95 computer on mine - it wouldn't shift the O/D (but it didn't in the donor truck either, so it is possible that part had failed), gave a water in fuel light anytime the accelerator was pressed part way, but it did allow the cruise control to work. My 91.5 computer had failed on the cruise, O/D and intake grid heaters, the latter two of which are easily bypassed.

 

[RSchwarzli]

These are all great ideas guys! Thanks so much!

He is going to do some diagnosing off of these ideas and will let us know (and I will post on his behalf when I find out what the issue was).

 

[DVolk]

I think a better choice would be a manual valve body transmission

 

[RSchwarzli]

I think a better choice would be a manual period and call it a day but....

 

[Philip]

Robert tell him to do the switch to ground test first. If that company couldn't fix the no OD problem in 5 weeks. Did they rebuild the trans correctly? He needs to determine if the trans does have a working OD first.


Any other testing is a waste of time till the trans condition is a known factor.

 

[Philip]

Any updates Robert?

 

[RSchwarzli]

Robert tell him to do the switch to ground test first. If that company couldn't fix the no OD problem in 5 weeks. Did they rebuild the trans correctly? He needs to determine if the trans does have a working OD first.


Any other testing is a waste of time till the trans condition is a known factor.

Very valid point.

Any updates Robert?

I sent an email with a nudge to see. He has been quiet for a week.