Hi guy's, I got a question for younz. A few years ago we swaped out the 7.5 rear with 2:73's for an 8.8 rear with 3:55's from a turbo coupe with around 200,000 miles on it. Right away I noticed something wasn't right, when I get it up to a certain speed it acts like it has a speed govener on it. It feels like it wants to go but at the same time it feels like something is holding it back. I know the trac-loc needs rebuilt but I wouldn't think it would hold the speed down, or could it? Last summer when I had it dynoed we found out it tops out at 90mph. The guy running it thought it had a speed limiter but it makes no sence because I once had it up to 130mph on a long straight away with the old rear, the way I know the speed is because I had a friend in an iroc Z28 running beside me that told me how fast we where going. So if it had a limiter it should've stopped it from going that fast back then. A couple other friends think it could be the fuel pump so I bought a BBK 255lph fuel pump for it. It's going to get put on this spring when it warms up.
I wanted to get some of your thoughts and opinions on what you guys think it could be and if you agree it could be the fuel pump. And if there's something else that could be wrong.
Thanks in advance for your help.
88's computers did have speed limiters.
lol. Are you sure about that????
Could it be the VSS signal is thrown off due to the now lower geared/numerically higher rear-end?
Was the transmission speedo gear swapped with the proper color/# of teeth?
Ryan
It might be true but I'm having a hard time believing that it has a speed limiter, only because it never held it back before. I don't know if you've seen in my sig. but it's a 5.0 car, if that makes a difference. The speedo gear was changed but it's still reading at least 10mph off, so something's not right there either.
The fuel filter will defenately be changed when the pump is. It is the original pump so it could be getting weak. 22 years is a long time even though it only sees daylight during the car show season.
Absolutely, and is likely the problem... With the 3.73 you need as many teeth as possible on the speedo gear... Fords longest gear has 21 teeth and that may not correct it on a 8 tooth output shaft tranny(which is what the car should have)...
If it accelerates without issue to the indicated 90mph, the fuel pump isn't the cause...
The '88s computers have a speed sensor input('87s do not) so I'm reasonably sure they do have a speed limiter, the '88 LSC does limit speed to around 105-110 mph and that's for sure(know someone that was using a LSC computer and he stated at 106 it stopped pulling, a SD 'Stang puter fixed it)... Guessing this may only apply to a 5.0 Bird/Coug as the 3.8 probably doesn't make enough HP to break 110mph, unless maybe going down hill... (http://antiqueradios.com/forums/images/smiles/icon_wink.gif)
I hope you guys will be patient with me, I've always been more of a detailer than a mechanic. I can do smaller things but when something big goes wrong I usually take it to a shop or have a buddy come over and help me out, which I'll still probably have him come over.
I had to look up what the VSS was, I honestly didn't think these cars had a speed sensor. The rear actually has 3.55 gears and the speedo gear was changed to a 20 tooth, but like I mentioned it's still off. Maybe I should also mention the car's a base 5.0 with the digi speedo. I don't know if that makes a difference or not.
So if I understand correctly, the speedo is reading fast which is making the VSS stop it at actual speed 90mph because it thinks it's going faster, 105-110. Is that correct? So how do I fix the problem? Do I need to get a 21 tooth speedo gear and hope it makes it read correctly? Or do I need to replace the sensor or both. Or is there something else I need to do.
Thanks again for helping guys! I do appreciate it! I'm just trying to figure it out so when spring gets here I'll know what needs done.
my v6 can go 110 mph in a straight line and down hill.
Your car does have a speed limiter, trust me. Mine did and when it would hit about 110 or so it would just stop. There are wires from the VSS to the computer. The nice thing about this is if you do a MAF swap (like I have) you don't have to run those wires;)
If you have 3.55s and an eight tooth speedo drive gear you probably need a 21 tooth gear (purple). With the 3.73s I have now (and the 8 tooth drive gear) I'm running an aftermarket 23 tooth speedo driven gear. I'm having the trans rebuilt in the spring at which time a 7 tooth speedo drive gear will be put in so I can run a 21 tooth speedo driven gear. This will make the speedo much more accurate.
Cool thanks, I'll get a 21 tooth gear for it and get it in. Hopefully that'll take care of it. I keep thinking of switching it to mass air, I have a set up from a 92 T-Bird. I got a great deal on it, $50 for everything, the harness, computer, the air meter, and air tube. I just keep thinking I'm going to wait until I either have the engine rebuilt or replaced then do it.
you do not want to use a 92 bird setup. Any 89 to 93 mustang computer plugs right in, the tbird one does not.
So I guess with the Mustang computer I won't have to change the harness? That would make things alot easier.
Me and Softtouch found a discrepancy between the EVTM and a wiring diagram concerning that with regards to the VSS in the 5.0 Cougarbirds.....
http://www.foxtbirdcougarforums.com/showthread.php?t=26707
VSS info
(http://www.transmissioncenter.org/classi1.gif)
(http://351winsor.com/joel/EEC-IV/Neutral-Extract.jpg)