1988 U-Joints?

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JudgeRusty

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For some time, I have had a concern about a sound (whine?) that comes and goes at highway speeds depending upon whether torque is applied to the drivetrain. When throttle is reduced to allow "coasting," the noise immediately stops.

Possibly related, when slowly going back and forward to hook up a trailer last week, I heard a noticeable clunk in the drivetrain.

I plan to check the u-joints as soon as I have time.

Online searches, and searches here, seem to indicate u-joints were same for '87 models and before and had the plastic injected u-joints from 1989 forward. I did not find anything specific to 1988.

Advice:
 

JudgeRusty

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Resolved (it seems). In the OP, I did not also mention a jingle at low speeds; it seemed to worsen lately, so I looked back into the driveline.
My initial mistake was thinking a tiny bit of play in the universals was OK; upon further reading I learned a little play is not acceptable.
Changed U-Joints and so far the noise is gone.
BTW, I did check the diff fluid level and it needed about 6 ounces.
 

movietvet

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But since the fluid was that low and you likely did not sample it, you now have no idea of the condition of the old fluid and the gears. Also, the fluid was low because of a leak. It does not evaporate. Axle seals, pinion seal or diff cover? You should pull that cover and inspect. You should remove drums and inspect.
 

JudgeRusty

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But since the fluid was that low and you likely did not sample it, you now have no idea of the condition of the old fluid and the gears. Also, the fluid was low because of a leak. It does not evaporate. Axle seals, pinion seal or diff cover? You should pull that cover and inspect. You should remove drums and inspect.
Agreed.

I purchased the gear oil and gasket intending to inspect the diff completely and change the gear oil, but decided to check U-joints again and was able to reproduce the offending noise.

With some confidence, I suspect Saturday was the first time the diff fluid was checked in 20 years. It does not leave a spot when parked, but the unit is dark near the lower cover indicating seepage at some time.
 

movietvet

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Agreed.

I purchased the gear oil and gasket intending to inspect the diff completely and change the gear oil, but decided to check U-joints again and was able to reproduce the offending noise.

With some confidence, I suspect Saturday was the first time the diff fluid was checked in 20 years. It does not leave a spot when parked, but the unit is dark near the lower cover indicating seepage at some time.
It is your truck. You are talking about 6 ounces. Unless you have no leak and was not filled properly the last time it was touched. That means the gears have not had the correct amount of "bath" to roll in. Did you pull the drums?
 

JudgeRusty

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It is your truck. You are talking about 6 ounces. Unless you have no leak and was not filled properly the last time it was touched. That means the gears have not had the correct amount of "bath" to roll in. Did you pull the drums?
Not yet, although has not been too long since brakes were gone through back there.
It's on my list.
This truck recently became my everyday driver again, so lots to catch up on.
I appreciate your encouragement and apologies for disappointing you. You and my father would have lots to agree upon.
I will return for updates and advice soon.
 
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