I just bought a 1996 Ram 3500 Cummins. Truck has just over 100,000.
The original window sticker says the truck has the HD 4speed option but
the sticker on the hood says std so not sure about that. The truck
goes in forward and reverse smooth and shifts smooth. The problem I
noticed is that right around 55 to 60mph (which also happens to be
regulated commercial truck speed) the truck seems to hunt or slip in
and out of what I think is OD with about a 300rpm change. I turned od
off to see if it would stop in it drops about 700rpm but is steady but
if you continue to slow down to say 30 or 40mph with the OD off it
hunts and slips the same so that is why I don't know if its actually OD
or not. But like I said at around 55 60mph with OD on it feels like
the OD is slipping in and out. Any speed above that it doesn't seem to
have a problem.
I checked the fluid level which was good but fluid smelt little burnt
so I changed it. That leads into a whole world that I have never
experienced. I have always had Fords and this is my first Dodge so I
don't know anything about the fluids. The dipstick says ATF 3 or
Dexron II. Everybody I talk to says never to use Dexron. The manual
says ATF 3 for 2000 and older and 4 for newer. So I went to Napa and
they told me to use the Valvoline ATF 4. Right on the bottle it says
it replaces ATF 3, so thats what I bought and a filter. So I really
don't know if that is the right fluid or not. Some websites say that
ATF 4 in older trans causes seal leaks but is better fluid. I changed
the filter and fluid (most fluid, just pulled pan) and did the
recommended band adjustment which was quite interesting. They put that
nice square adjuster on there so I had to make a tool to fit so I could
use my torque wrench. I followed the service manual and did the 72
inch pounds then back off 2 7/8 turns for forward and 2 turns for
reverse. So checked level and took truck for drive and it did the
exact same thing, no change.
I'm sure my next step will have to be take to a shop but was wondering
if this sounds familiar to anyone. It would be nice that by some slim
chance it was something simple to fix but I know with most trans
problems there usually not. Thanks for your time.
What you're experiencing is the torque converter clutch engaging and
disengaging - not the transmission slipping or hunting between gears. This
is almost always an electrical problem. As Roy said, your Throttle Position
Sensor could be going bad, sending a false signal to the PCM that thinks
you've floored the accelerator pedal, causing the PCM to unlock the
converter clutch. A shop manual or even a Haynes manual, and an analog
multimeter can determine whether or not the TPS is at fault.
However, there may be a simpler fix. As posted on the Turbo Diesel
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Lock Up Complaint: Issue 52, page 39, offered an in-depth look at torque
converter lock-up. Although the author was specifically talking about the
'98.5 and newer trucks, this tip applies to torque converter lock-up on
Turbo Diesels '94 and later.
As documented, many people have replaced the TPS or APPS, transmission
temperature sensor and numerous other parts trying to correct the ongoing
converter clutch problem with varying degrees of success.
Well, for all of the shadetree mechanics in Turbo Diesel land, before
replacing any parts or wasting time connecting a scan tool or voltmeter to
the electrical circuit, start with the easiest step first.
I have found the cause of the lock-unlock problem to be a frequency-induced
electrical noise into the ground circuit of the battery which causes a
fluctuating voltage signal from the TPS to the PCM.
The Solution: Locate the 10-gauge ground wire that runs from the negative
post of the passenger battery to the back of the alternator. This wire is
often tan with a black stripe.
Starting at the back of the alternator loom where the tan/black striped wire
heads for the battery, wrap the wire with a piece of tin foil about 4" - 6"
in length. Wrap the tin foil with black electrical tape to secure it in
Road test the vehicle. If the problem is corrected, smile.
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Thanks, this is good info. I cleaned all my electrical connections and
did the aluminum foil trick but that didn't help. I found an article
on-line with the specs for diagnosing the TPS so I checked mine and it
was way out of spec. I tried adjusting it and cleaning it but nothing
helped so I replaced it. After replacing the TPS I checked the idle
voltage and it was still out of spec so not sure what the problem is
yet. My reference voltage is 5.11 so that is good and I used the
ground wire going to the TPS to check the reference so I assume the
ground is good. I am still searching for the answer. Thanks for your
Finally fixed my overdrive/ converter issue. I have been on the TPS
warpath througout this problem because mine was out of spec. TPS
voltage should be around 1 volt at idle position plus or minus .2
volts. My old one was .33. I cleaned and adjusted and the best I
could get out of it was .59 so I bought a new one. I rechecked the
idle postition voltage which was still only .66 on the new TPS. I
drilled out the mounting holes a little and got it in spec with .81.
Thinking it should be fixed I test drove it and to my suprise
absolutely no change, still same problem. You can only imagine the
veins in my head. So after alot of thinking the one thing that I had
forgotten about was the fact that the cruise control didn't work
anymore. The power light would come on but would not operate. It was
at that point something clicked and I relized the trans and cruise both
have the brake switch in common. I replaced it and fixed the problem.
I blew alot of money on the TPS but like I said it was out of spec so I
got stuck in that rut and didn't think of anything else other than the
TPS and circuit being the cause. I will do alittle more diagnosis next
time even if something is questionable. Thanks for everyones help.
What a relief to have this fixed without replacing the trans. Thanks
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