[acfortier]

Hey all,

I recently had my '94 Mustang GT with a busted tranny replaced with a unit from an '00 4R70W V6 Mustang, but with all electronics from the '94. That has been great, shifting has been fine and smooth. But, not my speedometer is off, and I've tried different "toothed" gears but to no avail. Any ideas how I can get it to show the correct speed?

Also, I know that the oil pressure gauge on the cluster is supposed to just read smack-dab in the middle after the car has hit a certain PSI, but recently, at least after the tranny was replaced (can't remember before), it has been reading sporadically. Sometimes it pegs all the way to the black bar above the H and sometimes it reads 3/4 of the way. Never really seen it at the half way mark. Any idea?

And to continue the cluster problem, the temperature gauge has been sporadic too. Sometimes it will peg all the way to and past the red bar above the H, but nothing ever happens to the car. Usually when this happens, the pressure gauge is also reading as high as possible. But most importantly, I have noticed it fluctuate whenever I would accelerate in the car, or even turn on the blower motor from low to high. I'm thinking it's some type of electrical problem but wanted to get an idea.

The gas gauge and voltmeter seems to be reading fine, as does the tach.

If you can give any help, it'd be greatly appreciated. Thank you!

[Bullitt95]

Sounds like you have a grounding issue. An extra ground cable from the upper intake manifold to the firewall should fix it.

[furreal302]

Originally Posted by Bullitt95 Sounds like you have a grounding issue. An extra ground cable from the upper intake manifold to the firewall should fix it.

Agreed. The coolant temperature sender and the oil pressure switch both ground through the engine. Your speedometer I would suggest different gears but you already covered that so

[acfortier]

Ah, I will have to check the ground for that. Never knew. Thanks!

What would you normally have to do for a 2000 Mustang to change speedometer gears? I think it was electronic that year, so I am not really sure...

If it is reading HIGHER than it should be, does that mean I should get a gear with MORE teeth? Maybe I just haven't found the right one...

[acfortier]

Did as you said, fixed nothing. Oil pressure and temp. are still reading high.

Also, I put an ohmmeter on the sensor when it was at normal operating temperature and got a reading of ~ 31 ohms. Then measured voltage from the lead that goes to the top of the sensor to ground and I was getting about 5 V.

Any other ideas? I'm thinking the cluster is bad.

[Bullitt95]

Originally Posted by acfortier Did as you said, fixed nothing. Oil pressure and temp. are still reading high.

Do they still fluctuate when you apply an electrical load?

[acfortier]

Yes, still fluctuating quite a bit.