A friend of mine has restored a 1968 Ford Mustang GT500 from the junkyard, he started when he was 13, and is now 18. He knows the car in and out, as he pretty much brought it back to life-its in everyday driver condition...Now to the point. Upon reaching 95 to 100 mph, which is around 3500 in 4th gear, (4spd auto) the car simply wont accelerate. It feels like he is bouncing off of a rev limiter, or some sort of governer. We thought it was a coil at first, which was replaced-then we thought it was the distributer-adjusted and the problem is still there. The car will accelerate over 4,000 in the first three gears. Oil is changed, as will transmission fluid. Engine is a 302 bored 40mm over. Before we take it to a shop or do an engine pull, does anyone have a solution?

 

Fuel, Air, or electrical. Check your fuel lines/flow. Check your timing(vacumn advance?). Check fuel line placement if its at a place that gets too hot could be boiling the gas.

You have to make a list of what causes this and then cross them off.


paul

 

Called a mechanic and the mechanic said to check the transmission, which is vacuum operated. It hasnt been checked in a while, so hopefully this is the problem. We had checked the timing, and it was fine. Like I said, neuteral-fine,1 fine, 2 fine 3 fine 4th 3,500 goes to 3,600 then lurches back down again. Thanks for the advice, we will check.

 

Auto transmission? Could be the torque converter. Also check the fluid level again.

Paul

 

So what was it? ANy new info?


PAul

 

He called around at the time I was posting; and he had already come to the conclusion that it was torque converter, or the whole transmission. We took it in, got the torque converter flushed, (the main point), and other such things as fuel lines re-routed and covered and timing checked. When we drove it, it was an improvement to find the car did accelerate 85-90, but only on certain occasions. ( which erked us), and then on new years eve, the car just stopped in the middle of the road ( !) due to the fuel lines. The only improvement on the car that I noticed was that everynow and then it would go past the mark. Dont know if the mechanic service really helped. Do you know the problem-is it time for a new transmission?
(although the towing/pushing of the car was sort of a "mini adventure")

 

Confusing picture you have here. Could also be sediment in the gas tank.

Is the engine running fine? What exactly does it do at the non-accelerating times?

I'd personally take it to a tranny guy. Have them check it out. I had a Chrysler van and the torque converter died similiar symptoms, also had low ATF fluid gave similiar symptoms.

Time to call in an expert, bite the bullet and get some real help.
And post a pic


Paul

 

The engine is fine, idles fine, everything is normal. Timing is right, no white smoke or anything when the car is stationary. Well accelerate fine, to any RPM in any gear until 4th, when at around 85-90, or around 3500-3700, the car just wont accelerate any more. just wont. it then lurches back down a couple or hundred rpms, and reapeats the process. If you shift into 3rd, the rpm shoot down until your at 85-90. Just wont accelrate past that certain speed. Stock transmission, if thats what the problem is. Ill post pics sometime soon. Just annoying when you have a beast that wont go....

 

Sound's like a tranny problem. What tranny is it? I think Iwould also check the vacumn lines. But get the tranny model and I'll ask my dad a hot rodder late 50's, Mechanic etc. He helped me cut my teeth as back yardmechanic.


Paul

 

transmission is stock 4spd auto, not sure of the type and designation number, but what leads me to believe that the problem maybe in the transmission is because although it has been serviced, it is (i think) the same one that came with the car in 1968. But I just can see how a transmission can prevent a car from accelerating-like I said, it doesnt feel like the power isnt there, it feels like it bounces off a virtual (and mildly violent) rev limiter.

 

JUst got off the line with my with my dad, He said tranny problems would be all the time. He said if it can burn out no problems to 80-90mph, he said sounds like a fuel problem.


I have a kawasaki 550 motorcycle that had a similiar prob. It was the gas tank rotted out and pieces of rust clogging everything. Plenty of gas around town but as soon as we hit it lose power as the float bowls tried to fill. Check your fuel filter, carb, fuel pump and check your gas tank.


Paul

 

Problem is im stuck here at school, but the weekend of the 21st Ill get my hands on the car. (and on a camera). Like I said, the car is fine, no rough idle, backfire, just the mysterious in ability to go past 80.
the owner (patrick) said he 68 falcon with a manually transmision, which will probably be the next project-a manual conversion. maybe that will solve the problem..

 

Cool. Just post back what ever you find out. Curiosity is one of my stronger suits.


Paul

 

Try the Muffeler. Take it off and see what happends to the performance. If that's it ,I wouldn't waste time trying to clean it out. Go w/ a flow master or another performance unit. It will pay for itself in no time w/ gas savings.

 

The car is is being rebuilt now and is in peices. Disc brakes were added over the weekend, the car is being completely re-wired, and the engine is being rebuilt. The engine was finished last night and the car should be done in about a week. Will add an oil/transmission cooler, as the the transmission was getting a whole lot of unnessecary heat.

 

That would probably be a C4 tranny.

(Qualifications here: 428 CJ/Ram Air/4sp/3.91 TL Cougar, 68 1/2)

If it was bad gas or sentiment in the fuel, that would be all the time.
If it were exhaust, same thing.
Same with spark.

I vote for gearing/tranny problems, because it only happens at a range of speed and RPMs. Of course, with additional speed and RPMs you also get (as someone previous mentioned) higher temps in the engine...so vapor lock is a possibility. Unless there is some other variable that we are missing (additional vibration at the high speed?).

These cars are very simple to work on...like someone else said, spark, fuel and air...