Bad DMF or something else?

[Coyote_Red]

Been a while since I posted here guys. I started following the Facebook page more and the forum less but still think this is the best place to get an answer to the question you ask and not storries about their cousin's friend's brother's ex-girlfriend's grandpa's truck.

I have a factory turbo engine with a 4x4 ZF-5 in my 88. I have noticed a weird rattle/dry gear/dry bearing/dry chain kind of noise when I would be in 4th cruising with a constant speed and throttle and stay even with the clutch in slightly. Now it has moved up to very faint in 5th as well and only those two gears. I still have a DMF and am NOT changing to a SMF right now. The springs were tight and showed no real wear when I put the flywheel in. I don't believe I have signs of a bad dmf, no shaking at shut down, no chatter letting off the clutch, no imbalance sound at idle. I haven't noticed and leaks coming from the transmission or transfer case. The noise is coming from the transmission area of the truck. Do any of you guys have an idea?

 

[hoodshauler]

Sounds like you may have a bearing going bad in the transmission!

 

[Coyote_Red]

Wouldn't that be something you would hear in all the gears though and wouldn't it still be there regardless of acceleration or not?

 

[hoodshauler]

it would all depend on what bearing it is. When you say you hear it in 4th and now starting to hear it in 5th is it and low speed, high speed or any speed? it could also be your throw out bearing rattling I had that happen to me, it drove me crazy till it finally went out.

 

[79jasper]

The way it was explained to me was since 4th being direct drive, that's typically a sign of failing bearings.


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[riotwarrior]

Dmf check is easy...pull inspection plate....wiggle dmf forth n back...if real tight not likely cause ...if sloppy could be and likely is dmf.

 

[IDIBRONCO]

From my experience, you hear the DMF rattle when you shut it off. Sometimes a bad DMF will also cause a slight vibration at start up because it's bouncing back and forth on what's left of the springs.

 

[Coyote_Red]

it would all depend on what bearing it is. When you say you hear it in 4th and now starting to hear it in 5th is it and low speed, high speed or any speed? it could also be your throw out bearing rattling I had that happen to me, it drove me crazy till it finally went out.

I forgot to mention that my throw out bearing was chirping like it wouldn't release completely from the fingers when I first got the truck on the road but now it seems that the noise from that is gone now.

So I did some testing on the drive home tonight. I don't have a tach but by the speedometer it is mostly around 40-45mph in both 4th and 5th. When the noise would appear if I pushed the clutch until it would slip the noise would go away. I got on a smooth section of road and could not get the noise to come back regardless of speed or rpm. holding the same speed I hit a bump and the noise came back and stayed until I clutched in. after that I could coast at 45 down to about 40 and oscillatethe rpm and it would be faint. sitting in the driveway I could not get the noise to come back regardless of rpm. this noise is an intermittent one and not always present or continuous. I may try some new ATF and adding a little extra. it is currently running dex/merc at the factory fill level.

I will check the DMF in the next day or two but don't hear anything that sounds excessive for clatter at shut down.

Thanks for the suggestions so far guys. I really don't want to pull the trans for a second time in three months.