Just bought a 95 psd its a ex cab, auto, with a 4 inch lift and 275 tires (I know small). It has 189000 and runs great other than once I hit 72 mph there is a vibration throughout the entire cab alot more noticeable while towing and lasts tell 76 mph then tappers off any ideas? It has 4:10 gears and only does it at that speed. I can give it any amount of throttle at any speed up to 72 and nothing Anybody had this issue? doesn't feel like a tranny. Had a cummins auto so I know when its going out had it happen three times with that truck!

 

I had a center bearing cause the same symptoms. If you have a 2 piece drive shaft you might want to take a look at at it.

Was the center bearing shimmed when the lift was installed? If not it may wear out too soon again.

 

At that speed it's usually a tire balance problem. One good way to eliminate that would be to get on and off the throttle while it's doing it. If it comes and goes with throttle pressure, it's not tires. U joints and carriers are usually a low frequency vibration. Pinion bearing is a medium to high frequency normally. Look for oil leaking at the pinion seal on the rear end.

One other more common noise of this type is on 4x4 models with auto hubs. If they aren't disengaged after you use it, they make a pretty scary growling noise up around 60-70 mph. You almost always have to back up a little after putting it back into 2 wheel to disengage the hubs.

Also if some snot nose kid at a tire shop filled all your tires up to 80 psi because he doesn't know about the door stickers yet then that will cause it too. I really get ticked when people do that. Simple tire pressure has been the cause of probably 50 % of the alignment and vibration problems I have fixed.

 

U joints just replaced vibration comes and goes with throttle pressure how would I know if the drive shaft has been shimmed? Also any way to check the center bearing? Thanks for the input!

 

You can wiggle the shaft in the carrier bearing and if you see more then roughly 1/2'' in movement up/down, side/side then its more then likely gone to sea. As far as being able to tell if its been shimmed, you'll know cause there will be some spacers between the carrier bearing housing and the crossmember. Good luck

Cowboy Steve

 

Usually on that center bearing by the time most people complain about them the rubber has seperated form the mount. That's a pretty bad vibration.

I would look at the rear end if you don't find the problem there. Pinion bearings aren't very common on Ford rear ends, Especially this one. I do think it was a lot more common on 3.55 ratios than 4.10's but I'm only basing that on ones I worked on. Chevy 4.10's are terrible about eating pinion bearings.

If the rear has not been serviced lately you might want to pull the cover and check the spiders and then drop the drive shaft and pull the axles so you can turn the pinion by hand. You'll feel it right off if the bearing went bad. That's a relatively easy fix. Just keep the shims on the same side they came out of.
It comes and goes with throttle on the pinion because it's loading and unloading the two bearings on there. It's tendancy is to twist and put a lot of side force on the bearings, which causes the noise, when you are on it. Under no throttle it usually goes back to rest and the noise goes away. I've seen some though that sounded like a handfull of gravel was floating around in the oil though. If it get's to that point you will likely be replacing the ring and pinion too.

 

Well I checked the drive shaft and center bearing and there was minimal play in it. Also the housing was an aftermarket one that was installed with the lift it wasn't shimmed though just one solid pieace that is bigger than the one on my cousins stock truck. Guess it will be going to the shop for a rear end inspection!Anything else I should consider? Could it be the tranny? I would think it would act up other than just at 72 mph and above! Thanks for your input and help guys!!!

 

Most likely this is not tranny related. Have the rear end shooken down and go from there. Good Luck

Cowboy Steve

 

Does your truck have alum. rims if so get them balanced just had the same problem wieghts like to fly off after time.

 

I just had a crazy thought. The speed limit is only 70 mph. Since the vibration only happens at 72.........


It could be your driveline angles but I doubt it. Those vibrations usually happen at set frequencies too like a low moan at 30-40 mph and a nasty growl at 60-70 or so. Plus the frequency on a driveshaft not aligned right normally goes up and down as the shaft tries to straighten the ujoint out.

 

Speed limit on I 15 between SLC and Vegas is 75 Hate getting passed by big rigs! But can't stand the vibration! Get better milage though!

 

Make sure yor rim(s) are not bent. You can get a balance on a bent rim and have a distinct vibration, ask me how I know this. BTW I have a set of alum. rims 3 good, 1 bent with rubber make me an offer.

 

Sneal, I'll trade ya a TW chip......

Cowboy Steve