Well I have found an ASE Certified Mechanic that will plug in his tester into my truck and go with me on a test drive and see what his computers shows during the test drive he said it does a lot more than just read codes. He only charges 40$ for that, I thought for that price it’s worth seeing what it comes up with.<br><br> Subford: Do you think that is worth it? And do you know if that will test the PCM/computer?

 

Not sure what he has but if it is the Ford Rotunda Transmission Tester 007-00085 then it should tell if the computer is shifting the transmission or it is shifting on its own. If the computer is not reading what gear you are in then it will shift hard on its own.

The tester should also give what the computer is telling the EPC & TC Clutch to do if anything.

 

ok cool. i will let you know what he comes up with on friday.

- Joshua

 

Well I took my truck to a mechanic and he found a code that said there was a short in the VSS so he looked up the wiring diagram and it looks like the VSS goes to the speedometer then back out to everything else. So on a whim I decided to go to the junk yard and pick up a new speedometer cluster and replaced the speedometer and bam the problem was gone. I have test drove the truck all weekend now and still no hard shift.



But I am having problems with the a vibration comeing from what feels like the back end and I found that the rear end was a quart low on gear oil new thread at : Losing gear oil out of rear end. - Ford Truck Enthusiasts Forums


SUBFORD: could you take a look at the new post? Thanks you have been a huge help and saved me lots of time and $$.

 

Hi all, I'm new to this forum and to diesel in general.. I'm experiencing a similar problem to the transmission shifting discussed in this thread. I recently inherited my father's 1994 f350 7.3 turbo diesel auto trans crew cab. It has right at 180k miles. From what I understand the trans has been rebuilt not too long ago. I've experienced random hard shift here and there from 1-2 and 2-3. Some have hit hard even going into overdrive. Yesterday cruising about 70 it felt as if it clutched itself then slammed back together multiple times, every shift after that (yesterday) was pretty hard. So..... This morning I drove it to work, all shifting was harsh but not as bad as yesterday. Shifted harder at slower take off's, then cruising 50-55 I noticed it had the same symptoms clutching itself. I also noticed the mph needle jumping a little bit. On the way home today I paid more attention. It shifted as smooth as I ever felt until about 20 min into my 45 min drive home. As soon as I started reaching the 45-50 mph mark needle started bouncing a bit then the same symptom started. I took the next turn and getting up to 30-35 it acted up bad clutching itself with mph needle bouncing bad, I shifted to neutral then back to drive and it was fine. The rest of the way home it shifted fairly nice with a couple small hard shifts. I did notice that my temp gauge never changed and my oil pressure gauge is stuck. Any thoughts??

 

VSS (vehicle speed sensor) most likely.
you should consider buying an OBD1 code scanner.they're like 20-30 bucks and sold most everywhere.
if you need to replace the VSS tell the auto counter person to look it up under ABS sensor.they'll find it.
it's located in the top of the rear axle,held in by a bolt with two wires going to it.simple to replace.
if the trans can't see your vehicle speed,it acts up because it doesn't know your speed,if your speeding up,going steady or slowing down.with an electronically controlled transmission relying on this info,it doesn't stand a chance without it.

 

Thanks for the quick reply. Would you recommend that I purchase the code scanner and use that before purchasing and replacing the VSS? Also what do you think is up with the Temp and Oil Pressure gauges?

 

It sounds more like you have a cluster problem then a sensor problem.
The code scanner will not help you much as the code you will get will say you are getting a bad signal from the PSOM to the transmission module.

Come to think of it I do not think the code scanner will even work on your truck.

 

So you think I should replace the entire cluster with a new one or is there a way to trouble shoot wiring going to it? Wish I new more and electrical is my Achilles heel.

 

how can you tell if a jumping speedometer is due to a bad vss or the psom sub? what in the descriptions of his symptoms points more towards a failing psom?

MS,in '94 they offered two diesel engines.you didn't call yours the power stroke diesel.was this on purpose to imply it was the earlier idi engine? i shouldn't assume things.
(iirc in '94,the first/mid year for the power stroke,you very oddly couldn't get the auto trans anyway,but i can't remember all this crap lmao.plus who knows if she was a special order etc.etc.etc.best to double check and just ask.)

 

Not a PowerStroke. It's the 7.3idi turbo if I'm correct.

 

The two wires at the test plug are ground (sig rtn) and the MIL wire.

No I am not saying replace the cluster but you have a wiring problem or a ground problem. The first thing to look at is to see if you have a good body ground at the batteries. There should be at least a 10GA wire going from the NEG post to the sheet metal. This may solver your problem as it sounds like the body is not grounded.

Give me a few minutes to get back with you as I want to look up your cluster and I will post back.

 

Deleted deleted, wrong information.

 

sub,we don't have a computer controlled engine (7.3l idi) however the older OBD1 code reader pulls the codes from our devoted E40D ECM.
all idi owners with the E40D should start with making sure they have this low cost device in the tool chest anyway.regardless if the OD light is even blinking yet.so even if he buys the 20-30 scanner and it doesn't give him a VSS code,well he's not out anything.he's got it for next time lol.

 

Thanks for helping out. I'm very grateful. With my Fathers unexpected passing I want nothing more than to make sure his truck is in good running order. Thank you both!