Vibration while accelerating in 2nd gear.

[Mike92STX]

I have a 04 FX4 and it just started vibrating in 2nd gear. I jacked it up and checked for loose wheels and extra play in drive shaft and rear end. There is a little slop in the drive train. I've only had the truck for a few years, and it seemed like it was pretty well maintained except for the cam chain tensioners. I had the rattle at cold startup. My sons made me a deal and said if I get a remanufactured motor, they could replace it in a weekend. long store shortened; I have a basically. a new motor.
The milage is 257000, and when I checked for what might be vibrating the drive train looks like it is in good condition. Any ideas on what could cause the vibration? The cover on the rear differential shows some leakage.

 

[rusty ol ranger]

I have a 04 FX4 and it just started vibrating in 2nd gear. I jacked it up and checked for loose wheels and extra play in drive shaft and rear end. There is a little slop in the drive train. I've only had the truck for a few years, and it seemed like it was pretty well maintained except for the cam chain tensioners. I had the rattle at cold startup. My sons made me a deal and said if I get a remanufactured motor, they could replace it in a weekend. long store shortened; I have a basically. a new motor.
The milage is 257000, and when I checked for what might be vibrating the drive train looks like it is in good condition. Any ideas on what could cause the vibration? The cover on the rear differential shows some leakage.

Only in 2nd?

Torque converter maybe?

 

[Mike92STX]

Sorry, I didn't specify, it's a stick shift. My thought is either u-joints or rear end. Maybe bearings in the rear end. What confuses me is it just started. I have a 7 mile commute each way, mostly in town. I think it happens around 50 too. It's hard to tell because I only get up to that speed for a short time, when I don't see any police I haven't checked the differential condition or fluid since I bought it about 3 years ago.

 

[Mike92STX]

Well, the last 2 days I didn't notice the vibration, maybe I lucked out and it was just the old Cooper Discovery tires. They were on the truck when I bought it and they were in pretty good shape. The first year the seemed OK but after that they are not any good it the snow. I just checked the manufactured date, and it is 1115 so that makes them 8 years old. Probable dried out. I'm going to change the diff fluid and inspect the gears and LS parts for any excessive wear or damage. I got 75-140 Valvoline and the additive for the ls. Does anybody have any other suggestions on what could have caused the vibrations?

 

[rubydist]

I would also take a look at the u-joints and make sure that one of them is not sticking.

 

[superj]

does your drive shaft have a center support bearing? they tend to allow movement when under heavier load, like first and second gear versus later gears.

usually, the rubber that keeps the bearing centered will become all cracked and break apart allowing the center bearing to flop around and make that vibration.

and sometimes, most times, there is also a noise. not always, but mostly

 

[Mike92STX]

I checked the universal joints, and they didn't appear to have any movement. I have a 1-piece drive shaft. I'm going out to change the lube in the rear end in a few minutes. If it looks OK, as in normal wear I'll take a closer look at the universal joints. I haven't noticed any vibration in the last few days so maybe just questionable tires, they are 8 years old, I saw someplace that Cooper tires dried out quick so it might be time for new tires.

 

[rubydist]

A sticking u-joint will not have movement - that is the issue. To test, you need to chock the front wheels and lift the rear wheels off the ground and rotate the driveshaft by hand to see if there are any places where it wants to bind. While you are doing that, you can see if the center hanger bearing is loose and floppy if you have a 2 piece driveshaft.

 

[Mike92STX]

When I did my first inspection checked the u-joints by spinning the drive shaft and trying to move the u-joints and didn't notice any unusual movement. Yesterday I changed the fluid in the rear end, I turned the whole drive train using the ring gear to inspect the gears in the rear end, didn't see any unusual wear on the gears and it looked like the washers and c-clips were still in place. While cleaning the cover I noticed some unusual brown lines on the inside of the cover and the outside was damp in one spot after spraying the whole thing with brake cleaner, took the air hose and blew air on the wet spot and there were spots on the inside where it was oozing right where the brown lines were. I had to take an extra hour to get a new cover and the silicon sealer, because mine had dried out. I took it for a 5 mile test this morning and there wasn't and vibration. I guess I need to update my account, I sold the 92 STX with the lift and 35s and show that I have a 2004 FX4.