I'm not sure where you get your information about Ford SHO's and the Yamaha racing motor in it, but I will scan the service manual pages and post them up here to show that yes, my fuel guage is set 4.3 gallons lower than what is in the tank to keep my high flow racing fuel pump submerged. I expressly said I didn't know if that was the case with this truck, but I know for a "way" FACT that is the case with my SHO. Please, stick to what you know. I've never told you that you were "way wrong" for ordering people to put tranny fluid in their engine. Thank you.

 

Originally it was more of a gut feeling that I wasn't traveling as fast as speedo indicated, but then I've run past a couple of the police radar wagons (you know, the trailers with the radar and the speed display) and they consistently show that I'm traveling 3mph slower than what my speedo indicates. Obviously it isn't a precise estimate, and I know all about the inaccuracies of radar "guns" in measuring speed of travel, but it's pretty decent empirical evidence that suggests an inaccuracy with my speedometer.

As for the ultragauge, I've looked at it a couple of times but I'm not sure I see how that will correct the problem I'm having with the incorrect speedo. The ultragauge is still going to rely upon the information being sent from the sending unit and if that isn't correct, the ultragauge is going to be incorrect as well. The only thing I can see the ultragauge doing is allowing me to "adjust" the display to account for the speedo inaccuracy which isn't really a good solution.

 

I see your point. I assumed the inaccuracy was not with the ECU or sending unit (and I'm not exactly sure how the car measures speed), but with actual speedo display itself. The computer might be reading the correct speed of the car, but because the speedo display itself is analogue (i.e. not an exact digital display) the inaccuracy probably lies with that. I guess there is no way to tell for sure without hooking up an ultragauge and finding out. But it sure beats the price of a buying a new speedo or sending unit and having it installed. For what its worth, both my tach and speedo are off slightly to what my ultraguage tells me. By about 100 rpm and 2 mph.

 

Good point. I've been thinking about getting an ultragauge anyway just because I wanted to have some accurate mpg readings and temp data, so maybe this will kill two birds with one stone.

It'll be interesting to see whether the computer data tracks with what the speedo is displaying and with what the fuel gauge is showing.

 

My ultragauge reads my fuel level correctly (within .2-.3 gallons, as judged by the meter at the gas station), even tho on fillup, my fuel gauge never reads above 3/5 full, and hits empty when I still have 10 gallons left. If you're really that concerned about the fuel gauge, pick up a new pump and install it. There is a write-up somewhere on the internet on how to replace it. I did one in my friends 01 Disco, it really wasn't hard. It just takes a while to pull all the trim off the back and pull the carpet back. It's basically just a drop in after that. You have to determine which pump you have tho, there are some for an EVAP system and some without. If you call AB and give them your VIN, they will tell you whcih one you need.

 

Also, when we did it, we cut a hole in the sound proofing and then another in the carpet where the access door is, then neatly screwed a piece of black square plastic over the hole, so the next time it happens, we wouldn't have to go through the process of removing it again. Sure, you can see the piece of plastic, but you would never know it wasn't supposed to be there.

 

I think I'll go the route of the ultragauge first and see where that gets me. The gas gauge is only an 1/8th of a tank off so it isn't a HUGE issue and the speedo inaccuracy just means that I won't get a ticket (who gets a ticket for speeding in a Rover!?!).

If the ultragauge (that I was planning on getting anyway) reports the same inaccurate data, then I can look at replacing some of the other items.

 

You are new on this forum so I am going to let that reply slide.
I have seem a few of your posts, and for someone who know's little about Rovers, you have a lot of learning to do before you start giving too much information.
Take it for what it is worth and sit back and learn.