Hello people,

I used the "search" feature, but after a couple of hours, I didn't find anything describing my problem. So I apologize in advance.

I just came back from California, and I towed my 1971 Acadian there and back from New Mexico.

The truck developed a vibration under load, but more pronounce around 60 - 65 MPH. I first noticed it, because of the high-pitch rattle it was causing on the exhaust hangars/heat shields.

When I took the overdrive out (by pressing the button on the column shifter), it would instantly go away and pull the load uphill no problem.

When at level ground, it would not vibrate. But under load it did, and it would get worse if I pressed the gas pedal.

It would also NOT vibrate on 3rd gear, of course. This problem has been a real head scratcher.

It did the same thing when I got home and removed the car off the trailer...and yet, it did the same thing when I drove the truck not towing anything.

Now, I am a big promoter of K.I.S.S.'ing the problem, but I think that I am able to rule-out U-joints on the drive shaft, tire balancing, and simple things like. And what has gotten into my brain, is the fear that the torque converter may be failing/not locking all the way.

Also, for about a year and half, when it goes into third gear on the freeway, it shifts, and hovers around 2k rpm (31 inch tires) for about a second or almost two seconds (but really it does seem more like a second), before the RPM drops to about 1,600 rpm.

I must admit that my Ford experience is very minimal, and I own GM cars, but I do love my Ford truck.

Does anyone ever faced this problem?

It makes for good motivation for purchasing an F-350, but I like no payments much more...

GerryLP

 

How did you rule out u-joints?

And yea I know the feeling, been thinking of a F-350 myself, nice no payments though........ on the other hand a nice new or near new F-350 would be nice!

 

Well Dan,

I did peek underneath, and I did not notice anything terribly wrong with the u-joints.

But besides that, even when the truck would maintain the cruise control speed pre-set, the vibration would instantly disappear when I took the over drive out.

I almost went for the ,"cash-for-clunkers", and bought an F-350, but I tend to drive my truck mostly in the Fall and the Winter, so when I parked it off the street, I would take it off the insurance, and that created a break on the requirement by the old CARS program, for my truck sat un-insured for about 5 - 6 months.

but not payments are nice too....

GerryLP

 

While I agree what you stated tends to rule out u-joints as the problem I'd still give them a good going over just to be sure.

Taking the shaft out to check them is the only sure way to know for sure if they are good.

Did you check for trouble codes? If its a converter clutch slippage for example or anything of that type problem it should give ya a code for it.

 

Not yet. We have been having some late monsoon rain the las few days. However, it will definitely be worth to find what is set. I'll take it to Autozone, and let them connect the code reader..

GerryLP

 

You can do it yourself without a code reader if you want to, might be best as you don't need to drive it anywhere to do so.

How to run a self test> http://www.fordfuelinjection.com/?p=13

 

Thanks for the link, Dan.

It is more simple than in the book (I had to read how to hook them up about 3 times... ) And using the digital multi-meter, was a pain, for the codes a flashed and the voltage read-out not as quick, so it was harder to keep count.

I will try the circuit tester light...

GerryLP

 

Dan,

On the way home on my commute today, I also noticed that the vibration goes away, if I momentarily back off on the throttle...

I will shoot the codes tomorrow as well.

GerryLP

 

Did you know NOVA stands fro "NO GO" in Spanish? What my neighbor told me about his 69. LOL

Lets see, 71 Acadian, Canadian Nova, What does that thing weigh? 3500 to 4000 pounds. Add the weight of the trailer.

New Mexico to California and back.....That would be what, 1600 miles with some pretty healthy grades to pull.

You are aware that you are supposed to turn Overdrive OFF while towing don't you? You may have damaged the tranny or converter. That is what your symptoms suggest. Shift out of OD and the vibration stops.

Just a guess and I hope I am wrong.

 

yeah, 3,200 pounds..., and you may be right, but I have towed with this truck similar weight within similar distances (upwards of 2,000 miles) in at least 7 occassions. Never a problem. And it has 157,000+ miles, so not bad. I'll double-check what the owner's manual says.

The New Mexico Rig Express




I will also check the u-joints tomorrow again, but I do suspect the tranny/converter

Maybe I should get a Monster Tranny as replacement...
http://racetransmissions.com/store/p...roducts_id/265

GerryLP