1992 2.3 4x4 driveline noise when engine breaking

[murben]

I just acquired an incredibly clean 92 2.3 4x4 5 speed with 78k on it. Everything seems to run well and work as expected, but I've noticed an odd driveline noise and I'm not sure if it's anything I should be concerned about. When decelerating and using engine breaking, there seems to be a bit of a grinding noise coming from somewhere in the driveline. It happens regardless of the gear. If I'm in neutral and release the clutch pedal while coasting, there's no noise. If I push the clutch in, no noise. If I press and hold the gas pedal just a touch, the noise goes away, and if I'm just coasting in gear without any engine breaking, there's no noise.

Should this noise be concerning? Any ideas where I should start looking? Other than the noise, it seems to drive and shift perfectly. I do know that about 5000 miles ago the truck had a new clutch installed and the flywheel was resurfaced, along with a decent amount of other work.

Thanks in advance!

 

[scotts90ranger]

Not really pointing to anything to me unless there's a U joint mad but it would be mad the other direction too... It is pushing the transmission internals the other direction than on power but that isn't really pointing to anything I can think of either unless the pocket bearing between the input and output shaft is mad...

 

[sgtsandman]

While you are checking out the u-joints, look to see if you have a two piece driveshaft or not. The support bearing could be going bad if you have a two piece driveshaft.

 

[SenorNoob]

So the difference is whether the engine is driving the transmission or the other way around?

 

[murben]

I climbed under the truck and all u-joints seem to be good. No movement at all. Single piece driveshaft. I also checked the transmission and transfer case fluid, both good. The rear differential was about a half quart low so I topped that off. Yes, the noise only seems to be present when the transmission is driving the engine. The noise isn't extreme, just enough to notice it especially with the windows down and think "that doesn't seem right".

 

[sgtsandman]

I climbed under the truck and all u-joints seem to be good. No movement at all. Single piece driveshaft. I also checked the transmission and transfer case fluid, both good. The rear differential was about a half quart low so I topped that off. Yes, the noise only seems to be present when the transmission is driving the engine. The noise isn't extreme, just enough to notice it especially with the windows down and think "that doesn't seem right".

Tight u-joints is good but they could be still binding up if the grease in the bearings has dried up. The only way to tell is to drop the driveshaft and manipulate the joints. You can just do one end at a time, if you like. If they are overly stiff or notchy and grinding, that would more than likely be your issue.