I have a 95 F350 7.3 dually 5 speed that just recently developed what I would call a "chatter" in the transmission. The odd thing is it does NOT do it at all in 4th gear. 5th and 3rd are the worst. It is louder when you are slowing down and still have it in gear. All the gears go in and out smoothly and it performs well even with the chatter. It also seems to chatter at around 2,000 rpm then start to fade away as you raise speed and rpm and then if you lift the accelerator it comes back. I have had someone suggest that it may be the synchronizers but I wonder why 4th gear would have NO PROBLEM whatsoever. The clutch is getting old but still performs well and doesn't slip. If anybody has experienced anything like this could you please advise. I changed the transmission fluid today just because I felt like it needed it and there was no change. Thanks

 

It is NOT a synchronizer.

Have you checked you oil level and condition?

It uses ATF, I recommend changing it

 

German engineering at it's finest.


The fact that it only chatters when there's no load on it makes me think bearing but x2 on checking your oil level.

 

I drained and changed trans oil and no change. Which bearing are you referring to?

 

Can you post a video of this noise?

If the truly stops in 4th then I would say your pocket bearing is going, this is a bearing the supports the front end of the output shaft and the race is part of your input shaft, when you go to 4th these two parts get locked together (hence 1:1 ratio) and the pocket bearing doesn't move at all.

To fix or even check this bearing your pulling the trans and taking it apart. Another clue if it's bearing issues is the input shaft will be loose but you will have to at least pull the trans back to check that.

 

It is $250 for ALL the bearings, Seals and Syncros.

If you have it apart, you do them ALL

 

Any of them. Now that I re-read the post I agree on the pocket bearing but generally speaking a bearing that's a little too loose will be fine under load but will move around and create noise/vibration when not under load.

 

I just took the truck to my mechanic who works only on 7.3 diesel Ford and knows them like the back of his hand matter fact this was his personal truck for 14 years before I bought it . He seems to think it's something he called I believe the blocking rings in the synchro's. at first he was thinking the same thing either the pocket bearing or the pilot bearing but after driving it he said he didn't think it was noisy enough for those two things to be the problem . He is also thinking that it has probably been doing it the whole time and I'm just noticing it now because my boot around the shifter is cracked and leaking where I don't think it was before when you cover up the boot you really can't hear it anymore so his theory could be correct . He seems to think at this point anyway it's nothing to be worried about so I hope he's all right

 

How did the fluid look when you drained it?

Are you using SYNTHETIC ATF (required by ZF)?

 

it actually looked pretty rough very dark almost didn't look like ATF but it smelled like it and it was somewhat burnt. I replaced it my understanding is this transmission did not require synthetic I put regular dexMerc in it

 

Wrong. That trans DOES require synthetic

 

Yup. You can pour in dino but it won't like it and it will tell you fiarly quickly. It's German engineering at its finest.

I really would like to hear from someone who was in the room when that went down. I assume it went something like this.

"Hey Ernst, I know we said we'd design for normal ATF but I can save a few marks per unit, reduce drag by some barely measurable amount and allow us to run tighter clearances and spec smaller bearings that wouldn't otherwise survive if we spec it for synthetic ATF"

"Sure thing Heinrich, that sounds like a totally reasonable trade-off. The tiny improvement is totally worth frying a few hundred transmissions over. We should definitely be running the components of this transmission so close their limit that the performance difference between the two fluids is important."

If you're building a farm truck transmission that's so fine tuned that the difference in performance between dino an synthetic lubricant is meaningful you really need to evaluate your design decisions.

 

The very same transmission behind a 460 (well, same innards, different gear ratios, differemt case drilling) does NOT require synthetic. They obviously didn't re-engineer anything internally for spec behind a diesel. Whether that's ZF's fault for not doing so, or Ford's fault for not requesting it to be, is the real question. It may be more a case of:

"Hey Hans, y'know that 5-speed we've been shipping to those American Ford dudes to go behind their bigeffin' V8 460? Well they also want to put it behind an IH diesel they're shoehorning into the same truck."

"So did they provide any different internal component specs, Franz? Sounds like this one's expected to see more severe duty."

"Nope, they just said to drill the case for the bolt pattern of the IH engine (those silly Americans; they can't standardize on anything...). Fahh, let's just tell 'em to load it with synthetic lube; that should do it."

 

My 460 Zf came with a factory fill tag "only use Mercon Type H".... which (of course) was superceded soon after by Mercon V.
I'm running RP Syncromax, and I like it.


You don't hear anything in 4th, because 4th is 1:1.
All the other gears are indirect drive.
Is it hard to get into/pop out of reverse?

 

You guys done with the hyperbole?

Gears are gears, and likely don't really care too much about what kind of oil is used, as long as the viscosity is right. Synthetic fluid is almost certainly spec'd for the synchros to meet shifting performance targets and to increase overall durability of the transmission behind a diesel engine.

There are many people with tuned 7.3s that put a lot of power through ZF5s and ZF6 without issue, so clearly the parts are not "close to the limits".

Is it really worth crying about the extra $10 it cost to change your transmission oil?