Grinding in reverse when letting clutch out - zf5

[ComatoseLlama]

Hello,
I've noticed a new peoblem on my truck, I think it started after my clutch replacement. When I let out the clutch in reverse, with the back of the truck pointed up a hill, the truck makes a terrible grinding noise. It's not a synchro grind, it's a deeper sound than that. Once revs hit above 1000-1100 the grinding stops. It sounds like my trans is ready to crap itself.

Anyone else had this issue with their zf5?

Thanks, CL

 

[79jasper]

2 wd or 4x4?
You could be hearing the "normal" gear rollover from lugging.

Sent from my SM-N960U using Tapatalk

 

[Dane Rickford]

My new 3 inch down pipe contacts the firewall and makes a grinding/humming sound when I’m in the situation you described. Do you notice it when you do heavy engine braking down a hill?

 

[Garbage_Mechan]

I’ll second the downpipe (or something). My 91 does it in off road or heavy trailer backing. One day when I have it apart for something else I will make more room for the down pipe.

 

[ComatoseLlama]

My new 3 inch down pipe contacts the firewall and makes a grinding/humming sound when I’m in the situation you described. Do you notice it when you do heavy engine braking down a hill?

Yes this was an issue for a day or so! My downpipe was also a TERRIBLE time to bend around the top right bolt. This is probably it Thanks!

 

[IDIBRONCO]

You could be hearing the "normal" gear rollover from lugging

This would be my guess as well.

 

[aggiediesel01]

Double check your motor mounts. If they've never been replaced it's likely that the rubber bond to the metal plate has failed and allowing more movement than normal.

 

[IDIoit]

I had the same issue with my ZF5.
I cured it with a clutch rod heim mod and a firewall brace
brick nose firewalls crack

 

[ComatoseLlama]

I'm going to switch my truck back to ATF to see if it fixes it, I'm currently running straight 30-wt. Messing with my downpipe didn't help. Here's a video of the noise:

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[Garbage_Mechan]

Have an assistant apply torque to the engine in Fw and rev with the hood open and you standing to the side and observe if there is excess movement of the engine in the chassis. If so check motor mounts both the rubber for wear and the mounting to frame and engine.

 

[ComatoseLlama]

Have an assistant apply torque to the engine in Fw and rev with the hood open and you standing to the side and observe if there is excess movement of the engine in the chassis. If so check motor mounts both the rubber for wear and the mounting to frame and engine.

Will do.

New symptom:
Today I downshifted into third around 2200rpm and it made a similar noise when letting off the clutch, clutched in and went back into 4th instead and everything was happy.

 

[ComatoseLlama]

Just finished a road trip and the noise was much more noticeable when braking downhill in the Wyoming mountains. Engine braking makes the noise happen 100% of the time. Also grinds when I go over a big bump. It is much worse of a problem when facing downhill

I can’t see anywhere where it would be hitting the firewall but you can clearly feel it in your feet when you sit on the passenger side

Anyone had success fixing this issue?

 

[Philip1]

I had similar issues of grinding sounds in a cj5. It turned out to be failing internally which caused the transmission to lock up on me. So if you have eliminated all external issues (motor mounts, transmission mounts, exhaust pipes and other items smacking into things) i would look at the possibility of needing a rebuild especially if it happens at highway speeds where gear rollover noise is unlikely.

 

[franklin2]

What is the difference when going in reverse? What is the difference when engine braking? In both cases, the driveline is being torqued the opposite direction.

When you go forward, the engine and trans are twisting on the driveshaft, the driveshaft doesn't want to move at first, so the engine and trans mounted in rubber mounts torques the opposite direction. Till it runs out of motion and finally starts turning the driveshaft. When you are in reverse, it's trying to turn the driveshaft the other way. So the same thing happens, the engine and tranny try to turn the shaft the other direction and torque opposite of going forward. Decelerating is torquing the driveline the same as reverse.

So I think you have something rubbing or hitting, you just haven't found it yet.

 

[ComatoseLlama]

I had similar issues of grinding sounds in a cj5. It turned out to be failing internally which caused the transmission to lock up on me. So if you have eliminated all external issues (motor mounts, transmission mounts, exhaust pipes and other items smacking into things) i would look at the possibility of needing a rebuild especially if it happens at highway speeds where gear rollover noise is unlikely.

this is where I’m starting to think, the trans also slaps a bit when you let out the clutch sometimes. Started making a kind of bell noise when I accelerate at low speed. Anyone tried a rock auto rebuild trans?