So I have recently finished up a C6-ZF5 swap on my '82, but I'm having an issue that my mechanic is having a hard time tracking down. Here's the scoop-

So I bought a used ZF5 with everything needed to swap, and put it in. Went to test drive it, and as you let off the gas or are on very light throttle there is a weird rattling/grinding aweful noise for a few seconds. When you're at highway speeds its horrendos and unbearable. Drove it for 200 miles or so, checked trans oil and it was black. Figured i had a burnt bearing, so I bought a new ZF5 using this one as a core (my plan all along), and installed it. Same problem. The T-Case looks good, but on top of that the noise is coming from the front of the cab, not behind it. This noise is new to the truck, as the C6 did not have it. Nothing from the old ZF was brought forward except the crossmemeber, t-case, flex plate and driveshafts.

After looking at the flexplate I realized it was for a 351, so I put one for a 302 on there. The truck has a 347 Stroker in it, and it REALLY did not like this flywheel, not to mention the noise is still there. The motor is not right to begin with, so its at a local Ford guys engine shop getting rebuilt after the 2000 miles that are on it since the stroker kit.

Anyone have something that pops out to them that my mechanic should take a look at? Thanks in advance for anything and everything!

Brendan

 

What fluid are you using in the ZF5?

Single-mass or dual-mass flywheel? (1982, I'm guessing it's a single-mass.)

 

I wanna say the trans has synthetic ATF in it, it was whatever the trans shop said to put in it. If so, its Amsoil. As for the flywheel, i'm not sure. is there something visually specific that the dual mass has? The trucks 1/2 way across the country so i can't go look either. I remember the 351 flywheel that I took off had slightly larger weights on it than the one for the '82 302, but they looked exactly alike aside from that

 

Ok here is my thinking on this after reading.

This all started after the stick swap right?
You still had this noise with a new/rebuild trany right?
Pull the front drive shaft and test drive it still have the noise?
Check the rear drive shaft ujoints and angle.
My thinking is either the ujoints flexed more when out than normal when in the truck and a Ujoint is making the noise.
If the joints check ok then drive shaft angles might be off fromwhentheauto was installed.
Dave ----

 

I thought about that too, and the noise is constant in both 2H and 4H. The front shaft is also the same shaft as i had before, just lengthened. The rear shaft is the same as before as well, except I added a double cardan joint to help with that angle. Its definitely within acceptable angles now. I suppose I could pull the rear shaft next time I'm home, but I'm pretty certain that the noise is coming from much further forward than the rear shaft

 

Pilot bearing or throwout bearing? Flywheel rubbing on something (block spacer plate)? Driveshaft rubbing on something? Does it make the noise when revving in neutral or with T-case in neutral? Does it make the noise when coasting in neutral? I find it is best to try every combination of stopped/driving/coasting to try to determine what part of the vehicle/drivetrain it is coming from. Can you put the truck up on stands and try to listen/see where the noise is coming from if it only happens when the transmission is in gear? Troubleshooting noises can be a real pain.

When you mention it happens when accel/decel it makes me think of the engine torquing over causing a rub somewhere, I've had the problem with loose or worn out transmission mounts causing the driveshaft to hit and rattle on the muffler heat shield when turning. Also worn out engine mounts can cause the exhaust to hit things when the engine torques over. Not necessarily related but maybe it will give you some things to look at. Good luck.

 

Just a thought, what type of balance does the 347 crankshaft have?

Internal or external?

If external, does it have 28 or 50oz balance?

 

Any problems with the engine should show up while you rev it in the driveway. The pilot bushing only does it's job when the clutch is pushed in.

I like the driveshaft theory. My 89 has had this problem ever since I have had it. I know what it is, I just can't seem to get it solved. My problem is my front driveshaft. It only happens in 4x4 or when the hubs are locked in. Since you did not mention 4x4, make sure your hubs are unlocking, they may not be. Get someone to ease the truck forward in 2wd and see if the front shaft turns.

If it's not the front shaft, suspect the rear shaft. Mine won't do it if I am in 4x4 and are pushing on the pedal. It's when I let off the pedal it has this vibration it goes through and then it's ok as long as I am decelerating. Once I push on the throttle again, it will "pass through" the noise again and then it will go away as long as I have a load on the drivetrain.

I am pretty sure my problem is the incorrect angles between the front diff and the transfer case. I have just bought a double cardan driveshaft for the front and am going to try that. It's difficult to mess with the frontend without messing up the wheel alignment in the process.

 

Dave
Why a double cardan joint in the front?
The front angle is almost horizontal....
It's the rear that needed a double in the short-wheelbase configurations because to the extreme driveshaft angles.......

 

My truck has a 4 inch lift. The front shaft has a more severe angle to it than the rear shaft on my truck, it has a one piece rear shaft and a 8ft bed.

The 85.5-up f350's with the dana 60 came standard with a double cardan front shaft. That's the shaft I am going to try and swap into my truck. The front yoke on the transfer case may be a problem though fitting it up.

 

Just checking...thanks Dave

 

You will need a yoke for a double Cardan U-joint, you can't put a double joint on a single yoke (the holes on the single yoke are tight against the bearing cap for U-bolts to fit tight against the cap, the holes on doubles are spaced out from the cap to give room for some wall thickness for the threads in the U-joint that the bolts screw into).

You should be able to get a yoke for an F-350 transfer case (or get an entire F-350 transfer case).

 

So a little update, and some more info:

my mechanic had a similar situation 15 years ago with another zf, and remembered that he put a different fluid in it and it fixed the problem. He's going to put that fluid in it and check it out as a last ditch effort

I'll verify with him that the front shaft isn't the problem. its the same shaft that was in it with the C6 though, and the angle is acceptable, so I'm not hopeful. Not to mention that it doesn't matter if its in 2H or 4H, it still does it. Pilot bearing and thowout bearing are both new also.

The ford motor guy that will be rebuilding the motor balanced the flexplate to the motor, and it is as smooth as silk now. Unfortunately the motor still runs like crap. it runs crappy in the driveway too, so its for sure got its own issues. This 347 should be upwards of 400 hp, so the fact that it has a hard time getting out of its own way on the highway isn't comforting. Motor man wants to hear it run in the truck before my mech takes it out though, which makes me happy that he's thinking that way.

 

let us know what fluid he will use..