Hello, I'm new to the forums and just became a proud owner of a 91 12valve and just had a quick question. Is it alright for me to drive in town with my O/D off. Fastest speed is 50mph in town. The transmission feels good and has a receipt from bein rebuilt 7/2012, but it seems when i'm going 45mph-53ish that she's getting a lil confused on whether to be in O/D or 3rd. I turned the O/D button off and didnt have a problem. Was mainly wondering if O/D is mainly meant for the highway with these trucks or if I should be takin my truck in to have the tranny looked at Either way, I finally got a 12valve and I'm the 2nd owner. Thanks for the help guys!

 

I don't see any issues leaving it out but I had a 1993 with O/D and it shifted so smooth I could not tell when it went into OD... I wasn't sure if it was!! I paid attention and it seemed to go in OD at about 45. If yours is shifting rough maybe a good transmission shop should look at it... or maybe it's the TPS out of adjustment???

 

Yeah, I just got her and everything a couple days ago so I should probably take her to a shop anyways. She was still doin it in town today too. Probably get all new fluids put into her just to be safe then have the guys start letting me know what all i'll need to get back to how she was in 91.. Thx for the help

 

I would try making sure the TPS is adjusted first? If you have a multimeter it will be a free fix.

 

There is one at my work I can get to tomorrow.. Diesel is a whole new world to me, so i guess i'll start googling on how to adjust a TPS if thats what the problem is

 

Throttle position sensor. And I'm not sure if that's what it is, I could be wrong. I just know I had a 1993 with overdrive and when I bought it the previous owner, who lived on a dirt road (maybe it got out of adjustment easier going over bumps), went on and on about the TPS always going out of adjustment and playing havoc with the overdrive and shifting of gears, and until he figured that out, he'd have to pay $150 or so for someone to adjust it for him every few months. I never had to mess with it myself and sold the truck and bought my current truck that doesn't have overdrive.

I don't know if you're willing to fix things mechanical or not but a few benefits of owning an old vehicle is that 1) the 1st gen is a simple diesel motor that is "mechanically controlled" vs electrically controlled so it's easier to fix, 2) parts should be cheaper compared to a newer vehicle, 3) it's more likely to break down vs. a new car but if you're good at fixing things, it's cheaper in the long run to own one of these if you fix things yourself 4) if you have a mechanic fix things whenever there's something wrong you take away the first 3 advantages and may wind up with a money pit that way, 5) parts are harder to come by and it's not just a matter of going to your local Auto Zone, 6) 1st Gens have their quirks (like driver's door not wanting to close), and 7) I think most people who own a 1st Gen these days think very highly of them (Including me who is an old Ford gas motor truck convert who can't imagine owning any truck other than a 1989-93 Cummins from here on out).

All I can tell you is I've been working on cars all my life, 36 now, raced qnd worked on my own dirt track stock cars for about 7 years, rebuilt engines, etc, but new to diesels over the last year, can get into trouble with them, there are things that are different about them compared to gas engines, they take different tools, but there are people on here that know a lot and should be able to answer about most of your questions (surprised nobody else responded to your post), you can make your old truck an old low cost vehicle that can haul some serious loads when you need it to, instead of your local mechanic's favorite old truck that pays bills. Of course I don't know your background and all or what your goal is with this 1991 Dodge, wish to do your own maintenance/repairs, or if you are trying to save money and DIY, I'm just throwing this out there. Dieselbombers.com is a pretty useful resource.

 

Yeah, I found a post about it previously today after work. Probably why there aren't many replies. Thank you none the less for all the help haha, I found the TPS and everything and turning it CLOCKWISE just a smidge should decrease the voltage which will cause the shift to happen sooner.. Along with freezing rain and everything else bad luck today, the multimeter at my work was broke so go f***** figure. Im thinking if I just (barely) turn her clockwise then road test after I should be able to make adjustments just fine. Even on the highway with O/D on its like I have to get my RPM's to go so high for it to kick in and or stay.. Staying in O/D means accelerating. So I'm hoping this will fix it without having to spend money. Have a receipt from 7/2012 showing it was rebuilt.. So I'm sure this is all it is. Thanks again for all the help and knowledge. I'm 25 and got her this month as a birthday present to myself coming up on the 21st.. I pretty much want her to be a highway cruiser, but I also don't want to be the guy that holds everybody up on the exit ramp . I don't plan on ever getting rid of this truck, so as poor as I am. No money is to much to go into a truck like this in my opinion.

 

Update, its the TPS. Seems to be gettin worn. Just gonna install a TPS delete kit from DNR and have it to where i can set it for in-town towing.. Cheap fix instead of a $300 TPS sensor. Have read ALOT of good things about a Potentiometer so I'm going to that for now to atleast take care of it for the winter. Glad ya had me check the TPS. Seems just about everything on these are wrench capable which is amazing.. Now all I need to do is homework on how to adjust all this stuff to give her a lil more power.

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Update** So I found a local diesel mechanic, sadly he was out of town but was more than happy to also help on this subject. He mentioned I might want to check the VSS. He said sometimes they can get moisture in them and a notice is your speedo bein dead.. I've had it die on me twice in a week but only for a sec and when going under 15mph. My question is where is the VSS and if someone could link it to me.. I tried browsing that awesome sticky of all the 1st gen stuff but didnt see it.

 

I think the VSS is on the transfer case or tail shaft but I can't remember.. Either there or the rear end.. It's been a long time since I've been around my truck.