So yesterday was the day I finally put in my ZF. I bought it from an auto salvage yard and had it rebuilt. New clutch, pressure plate, flywheel with resurface, pilot bearing and transmission mount. Everything went very smooth with the install. Tomorrow i'll be getting a shop to custom fit the old drive shaft with a slip yoke for rear end travel.

So when I started the engine and was going through the gears (might be bad for it with no drive shaft but it was only for a minute or two) I noticed the transmission was making a clunking noise when engaged. In gear or neutral. the only thing that stopped it was pushing in the clutch. The rear seal was also leaking a little fluid. I added fluid until it poured out the fill hole so I know it's not over filled.

My questions are, Are ZF's naturally noisy like this? Is this common on a newly rebuilt transmission? Does it take some heat and time to seat everything properly? Was the noise contributed to not having a load(driveshaft)? Finally, will the rear seal need time to seat etc..?

Kind regards,
M_J

 

They are, generally, pretty noisy. Mine came from a junkyard truck with 200k on it...lots of gear noise at idle with clutch engaged (pedal not pushed in). Plus my third gear sounded like a chipmunk wanted to get out of the thing! put many thousands of miles on it like that before i scrapped that truck and the ZF is about the only piece I kept, going into my 96 once I rebuild it.

One thing: i don't know what fluid you used, and I know they recommend ATF, but I put 10W-30 motor oil in my beat-up ZF as an experiment and it was a lot quieter and shifted better

It also may need some road time to get the synchros and bearings lubricated.

Sorry, i just saw you say "had it rebuilt" ; in that case, it probably should NOT be making so much noise.

 

A constant clunking? It just might be lash in the gears with no load on it? (no driveshaft).

The seal will not need to be broke in. It should not leak no matter.

 

Gear roll over noise is quite common on this transmission. Clunking doesn't sound quite right Get it together and take it by the tranny shop that did the rebuild and see what they think.

 

I used valvoline synthetic ATF. I'll be returning the truck to the tranny shop to get the seal taken care of, and now that I have driven it for a day or two it seems to have reduced the clunking to almost non-existant. I'll chalk that up to being in need of break in or something of that nature. I still have the roll-over noise though but I know it's natural in a ZF. I kinda like it, actually.

 

I just did the same swap and before installing I found the synchros to be considerably under .024" clearance so i decided to break it apart and install new ones. Everything else in the trans was super clean, bearings and gears showed little wear and the magnet had little to nothing on it.

After carefully performing the syncro procedure: following the manual, etc. I get everything together. I did not install new bearings as I didn't have to damage the existing ones, and I didn't feel like having to dial in shims if everything looked good.

My 96 150 is up and running, I've put about 400 miles on it so far with the ZF and it drives well and shifts totally normal. I do find the detent to get into 1st to be a bit resistive, but I'm hoping this is just because it is a rather low gear and not to be entered on such a fly. Otherwise 1st operates nice and normal with no excessive noise or grinding in.

The one strange issue: Occasionally I get the strangest series of noises. They aren't "gear rollover" or "clunking" but a whack, clack, strip and clatter when I slow down hard from above around 40mph. (down a hwy ramp lets say) Doesn't matter the gear or N or whether my foot is in or out of the clutch. It's as if some of the rings are suddenly breaking away and spinning inside the trans on top of the hub. Not really possible I know, but this is the best description I can give. Its like they're chucking around in there. You can hear a whizz as if teeth are being contacted partially. These strange circumstances will sometimes affect whether it will grind when trying to enter 2nd from near a stop.

These noises I am hearing, (sometimes mild intermittent ones when in motion also) sound as if something is grossly wrong but I just can't figure what went so far off. Furthermore if this was a bearing or collar or spur grinding up, I would have already been towing it home, couldn't shift as smooth or heard things during acceleration or not in 4th, etc, etc... Every other motion of this trans seems tight like new so all i can say is "WTF????"

Maybe there is a break in period where the wear zone of the hub has to match the taper of the ring? The transfer case was another guess, but its the same case that was behind the M5OD. The weather has been pretty cold thru all this and despite the nice Mercon I filled it with, perhaps a lubrication/tolerance issue? Totally stumped here.