I've just purchased a used 95 Ranger 4 cyl, 5 speed and I'm getting a vibration around 40-45 mph when I let off the gas. It seems to be most pronounced in 4th gear, although it is noticable in 5th gear, leading me to beleive that the higher engine speed aggrivates the problem. I don't seem to be having any issues in 1st, 2nd and 3rd gear (nor would I expect to, since it seems to be more related to vehicle speed, not engine speed) If I disengage the clutch, the vibration goes away. I can rev the engine in neutral and there are no vibrations when I check it with an inductive tach at a similar RPM where the vibration would occur in gear. There is no vibration (apart from the typical rattles you'd expect in a truck with 128,000 miles) when I accelerate through the same range. There have been no suspension or drivetrain modifications to this truck, it is completely stock.

I'm thinking it might be one of two things, 1) The u-joints, driveshaft yoke, or center support bearing is worn or shot or 2) Bad bearings (although there is no whine, so I doubt this) or other problems with the ring and pinion gears.

Since I don't have much experience working on Rangers, I was just wondering if there is anything vehicle specific I need to look at. My experience working with and on other vehicles has pointed me to the above diagnosis, but I'd like any other pointers before I start pulling things apart.

Thanks!
Bart

 

Welcome to FTE Bart!

I'll try to let someone with more insight answer your question(s).

But FWIW, your thinking on it being driveshaft-related (u-joints?) sounds reasonable to me.

 

Well, looks like I might have found my problem...

I just climbed up under the truck and it looks like the passenger's side motor mount is bad. It looks a bit skewed compared to the driver's side one. It is still in one piece, hence why I'm not getting the tell-tale clunk associated with a busted mount, but it could very well be the source of my vibration nontheless.

I still welcome any other suggestions just in case this doesn't fix it though.

Bart

 

If you block all 4 tires with some "Big Lumber" or cinder blocks, etc, you can have someone engage the tranny and let the clutch out while you watch the engine mounts. Do it in forward and reverse. If a mount is bad, you will see the engine move quite a bit. If it is OK, the engine will move a little, but not much. Don't kill the engine. You can also use a pry bar on the mount to see if it will move while the engine is not running, or jack the engine up with a floor jack. It could also be the transmission mount. My guess is a u-joint, hanger bearing, or dirty slip joint. Keep us posted. BTW, if you do the running engine check, stand off to the side and not in front of the truck.

 

Bart.....I hope you keep us informed. I have a '95, XLT, with an auto tranny, that has the same problem. There seems to be a lot of us out there with this vibration problem. I had all my u-joints replaced and a new carrier bearing installed and still have this vibration around 43 mph when I cruise. I think my motor mounts are good and suspect the entire driveshaft assembly needs to be balanced as a unit. The reason I think this is because I removed the front driveshaft and rotated it 180º, keeping the orientation of the rear driveshaft positioned to the original paint marks on the differential. This reduced the vibration considerably. Wouldn't you think with your suspected motor mount problem it would show up even worse under acceleration when the motor is under torque? But if I understand you correctly, your problem is more pronounced when you let off the gas. Any chance you can talk to the former owner? Anyway, good luck and let us know what you find out.

 

In my experience, a motor mount may be guilty of a vibration under acceleration or deceleration, depending on which mount is bad, and the direction of the rotation of the engine itself. In my case, the driver's side mount seems to be OK, and I beleive that the crank in the 2.3L rotates clockwise (I might be thinking about 4.6L and 5.0L V8s, so correct me if I'm wrong); therefore under acceleration the driver's side mount (if I remember my physics correctly) would be put under more stress. Likewise, in deceleration, the passenger's side mount would be under the most load. My mount only looks damaged, not completely broken.

Also, the fact that the vibration/rattle occurs only when the engine is loaded would somewhat confirm my theory of it being the motor mount. My guess is that a driveshaft induced vibration would occur anytime the driveshaft reaches the critical speed needed to cause the vibration, regardless if the vehicle is in gear or not.

I did get underneath the truck and make a visual inspection of the u-joints and center bearing and they looked OK, as in there were no parts missing or lubricant leaking out of either. There was no excessive play in the yoke into the transmission, and I didn't notice any kind of binding of the u-joints so far as I could rotate the driveshaft with the rear wheels on the ground. I should have more time to look into this over the weekend, since I will have most of my school related responsibilities taken care of by tomorrow.

I'll update this thread when I find out more.

Bart