Had the trans rebuilt about 1000 miles ago due to bad synchros and a missing tooth on the low/reverse gear. New clutch about 1500 miles ago, new master/slave about the same time. Last week I pulled my 35' 5th wheel camper on a 300 mile round trip. I noticed that when I was down shifting it would make a grinding noise, almost like when a brake pad goes metal to metal against the rotor but it was definitely coming from the front of the transmission area. It can be heard when not pulling the camper but it is much louder when pulling the camper, so loud that even my 6 year old daughter said what is that awful noise daddy! It does it the worst going from 3rd to 2nd, it does it a little going from 4th to 3rd, going from 5th to 4th it doesn't do it. I never down shift from 2nd to 1st to slow down so I don't know if it does it then. It only does this when downshifting to slow down. As soon as I downshift and let the clutch out it makes the noise. If I give it any throttle at all or push the clutch in the noise stops. It doesn't do it at up shifting or just driving in any of the gears. Any ideas?

I just got the camper and this was the first time towing anything that heavy with the truck. I had never noticed the noise before towing the camper on this trip. Trans shifts good through all the gears, clutch feels good. Nothing else seems out of the ordinary.

 

I would change your fluid and check it for debris but other than that I would take it back to where you had it rebuilt and let them know because that does not sound healthy and sounds like something is rubbing against something it shouldn't and it's only a matter of time before you find out what it is for sure.

 

I'll drain the fluid and check it out today. Seems strange to me that it only does it when downshifting and goes away as soon as I give it throttle or press the clutch.

 

Hi LSO1123,
I have the same problem with my 99 7.3 dually and I am very nervius obout it.I was thinking of changing my ATF with some heavy oil(75-90) and maybe adding some stabiliser as well and see what happens.Did you have yours fixed and if so,how did you fix it?Any info will be very helpfull.

 

Actually mine just stopped doing it on its own. I don't think the heavy oil is a good idea because I've read on here that the zf6 is only suppose to run on atf. Check with some others on here to be sure though.

 

Probably a few burrs on some gears. Glad yours 'fixed itself'.

I have a little over 25k miles on my Midwest Trans rebuilt/updated ZF6 and no problems whatsover. Maybe its because I painted it?

 

That looks good! I bet if I had painted mine Ford blue it would have never had any problems! Mine only did it when pulling my 35' fifth wheel camper.

 

Lol. I have a thing about paint... Painted calipers, rotors - mostly things that RUST. I may never clean these painted parts, but they don't turn brown!

I stuck this in, drove a couple hundred miles, then hooked it to the 5ver and drove 5-600 miles at 22-24k lbs GCVW. More than half the miles on it are towing at that weight.

The Southbend Con OFE absolutely rocks BTW. The LUK sucked.

I'm also running a real roller bearing for a pilot bearing. Stock is a totally useless POS and the kevlar bushing is no more than a bandaid for the real problem.