1. Home
  2. Automotive Technologies
  3. 90 Dakota Transmission

90 Dakota Transmission

I had the overdrive section of my auto transmission in this truck turn into a nice soupy mixture of metal shavings awhile back. Since the truck had about 130K on it and the engine was getting tired, I ordered up a rebuilt V6 and tranny from aftermarket sources. The tranny I received was date stamped as an 89 model, but except for different sized fittings for the cooling lines, everything appeared to fit the same and it went back together just fine and is running.

I've rebuilt many engines, but I've never really gotten into auto transmissions before, but here are the symptoms of a problem that has come up. The truck holds a lower gear for way too long. When in drive, the rpms go to near red-line without shifting. To force a shift it is necessary to get the speed up, then let off the gas pedal a bit. At highway speeds, it runs just fine, so this issue only appears at low speeds. The second part of this problem is that the speedo now reads low. Before the transmission change, my GPS showed a perfect match to the speedometer, now it is reading about 5mph slow at highway speeds. If it were a standard tranny I would say that it is geared taller than the stock one was.

Any tranny guys out there who can provide some pointers on where to start with correcting this problem? I'm hoping it is some simple tuning stuff so that I don't have to take her to a tranny shop to do it. Hate to pay other people money to take care of mechanical stuff ya' know. It was quite a bear to get that tranny in there in the first place...

TIA, Scott

Reply to
Scott Aleckson
Loading thread data ...

speedo drive gear is wrong

Reply to
TransSurgeon

Hi Scott,

I don't have an answer, but feel your pain. I had a '95 2500 with the same shifting symptoms. I lived with it for 4 years since no one could find an answer other than replace the tranny. Letting off the gas to shift to second was a small price to pay as opposed to a new transmission. I wound up trading it in with that problem for an '03.

--Mike

Reply to
Michael Greenwood

Reply to
Scott Aleckson

The selectable speedo drive pinion gear matches the speed sensor output to the combination of rear axle gear ratio and tire diameter. It has nothing to do with shift points. The shift points are controlled, in part, by the throttle valve. The throttle valve is connected to the throttle by a cable or linkage that is adjustable. Adjusting the throttle valve linkage/cable so that the lever on the transmission is further forward for any given throttle setting will cause the transmission to shift earlier. John

Reply to
John Kunkel

IS the carburetor-to-transmission (or throttle body-to-transmission) rod or cable connected to the accelerator linkage? If not, the transmission has no throttle position reference and "thinks" you have the gas floored all the time (or somewhere near floored). That would have nothing to do with the speedometer not reading correctly- that would be an incorrect or incorrectly installed speedometer pinion in the transmission tailshaft.

Reply to
Steve

Torqueflites of that vintage don't sense road speed off the speedometer pinion. Road speed is determined by a mechanical governor on the output shaft inside the tail-housing. My guess is that you have two un-related problems. Check the kickdown/throttle position liknage as I mentioned in the previous post. A stuck governor *could* cause the same problem *if* it were stuck in the "stopped" position, but they usually stick in the high speed position if they're going to stick (not impossible though). If the throttle linkage is OK, then go after the governor. Requires transmission disassembly, though, so I'd actually "go after" the place you bought the trans.

Reply to
Steve

Why can't I ever find a truck like that to buy for pennies on the dollar? And do *all* transmission shops think T-flites work like TH350s and get stumped over stuck governors and mis-adjusted kickdown linkages? I gotta get out more :-)

Reply to
Steve

Yes this linkage is present and adjusted. I adjusted it exactly by the book when I installed it (yes, I have the shop manual). I did notice that there is a lot of lateral play in this linkage. When installing it, I was thinking they would have been better off using a flexible cable linkage instead of the bent steel bar. I will double check this linkage, and maybe try sliding it a bit one way or the other to see what effect that has on the shifting. Thanks.

Reply to
Scott Aleckson

MotorsForum website is not affiliated with any of the manufacturers or service providers discussed here. All logos and trade names are the property of their respective owners.