.

Man that statement just sent a shiver down my backbone Kris!

Like a bad case of De Ja Vu - all over again!

I'm constantly wirrying how my 4R100 aoto tranny will hold up to towing - but had in the back of my mind considered maybe if it failed somewhere down the track - rather than rebuilding it - I might buy ibn a new manual 6 speed and convert her..

Now with hearing about needle roller bearings again - I'm having second thoughts already, having walked this towing in overdrive rice paper trail once before as a younger towing ninja!

Cheers!

 

Well, what I found was 8 teeth broken on the overdrive gear. All of the bearings are intact and fine. Unlike the gearbox you mention, the ZF does not have an adjustment, per say. What you have is a spacer that you can change, to affect the relative position. I could not find where anything was running where it shouldn't, but having only parts of 5 teeth in one spot, and missing parts of 3 others a quarter way around would certainly explain the strange noises I have been hearing.

It is true that the far end of the countershaft, where the overdrive gear resides, is supported by a needle bearing (next to the reverse idler gear), and there is one inside the gear itself, the actual support for the shaft is in a tapered bearing situated in the spacer piece between the main box and tailbox, with another tapered bearing on end after third and fourth gears.

Why I have broken teeth is another question. I can't remember anything that could have caused this, so I guess I'll attribute it to stress. Maybe the extra torque from having a clutch that didn't slip pushed it over the top. That, and looking at the teeth, the overdrive gear has the smallest teeth, by far, of all the gears in the box. Maybe this is necessary due to the larger diameter of the gear, but they just seem less meaty.

Anyway, tomorrow I'm off to order a new gear, and then reassemble when it gets here. The only thing puzzling me is how to get the reverse and low gears off the mainshaft. The diagrams show a snap ring holding the ball bearing on the end of the main shaft (the driveshaft hub pushes right up against the race), but I can't find an end to grab. It looks like a continuous ring, so how do you get it out? It probably takes a special tool, which I will ask Ford about tomorrow.

I asked the mechanic to look at the pilot bearing marks, and of course, he said they were normal, just that the new bearing may not be riding in exactly the same place as the old. He even gave me another bearing if I wanted to change it again.

I'll post as soon as I get everything back together.

 

Get yourself a Kevlar pilot bushing and don't use the factory roller pilot bearing. The Kevlar units hold up great. I have over 100,000 hard miles on mine. And by hard I mean full throttle, smoke the tires, launches. Lots of em!

 

Thank you for getting back to us raduenz.
I'm going to see if I can get a look inside of my transmission somehow, perhaps through the PTO panel and then use a gooseneck light and a mirror.
With Christmas coming up, it won't be for a while I'm thinking, but I will definately return and report on what I found in mine as well.
Going on how you are describing it, I am guessing that you twist wrenches for a living.

 

When I replaced my tranny and clutch, I found little pieces of pilot bearing all over the bellhousing. Evidently, it had been washed in diesel fuel too many times... The truck had always had a... vibration? for lack of a better word. The shifter would rock back and forth at idle. Since replacement, it is smooth as silk. Clutch pedal is much better as well, due to the LUK upgrade. I wish, however, I had gone with the kevlar bushing. Oh, well.

 

No, I make my living as an engineer, but I have done my own work for the last 35 years, except twice (other than warranty stuff). I know, an engineer that can work on something mechanical!!! I have been through multiple complete rebuilds of engines and various trannys (auto and standard), and worked in a body shop to pay my way through college. I have a brother and an uncle that were mechanics their entire lives, so I can usually get good free advice. As long as I have a diagram to go by, I'll try anything.

The perfect example this summer was paying to have my clutch replaced. I should have done it myself, but just ran out of time preparing to go on vacation. Work has been extremely busy since we went through Hurricane Rita last year, and this spring and summer were even worse. And that was on top of doing repairs around the house (I live in Lake Charles, LA).

The irony was that when I talked to the mechanic yesterday, he told me that he was doing me a favor, because he knew we were leaving on vacation. That, and the fact that they got the wrong clutch the first time, and then had to scramble to get another one, pull the ttranny again and reinstall, so he said he wasn't surprised they left a few bolts loose. I guess it's alright to leave someone stranded on the highway, as long as you get their vehicle back on time. In my opinion, he just lost any credibility as a mechanic. Loose bolts are wrong, no matter what.

That just clinched that I won't put another vehicle in the shop. Then to top it off, my wife brought her Avalon to the dealership to get her first oil change last Thursday, and they forgot to tighten the plug that drains the oil filter housing. When she returned from a 150 mile roundtrip, she had 3 quarts left. Then they had the nerve to call for a customer satisfaction survey yesterday. You can't even trust people to do simple things anymore. I guess I'll be doing every oil change like her last car (95 Camry with 150K), that my daughter now drives.

 

Now I'm worried about my 6 speed. I have 155K miles on it and have developed a whine in OD. While I don't use ATF for a lubricant, maybe then 70w synthetic is masking a noise that would be much greater had I had ATF in there.

I think I'll follow Kwiks advice and pull the PTO cover.

 

why would you use 70w synthetic gear oil in a transmission that your supposed to use atf in?

 

Yes,

I too lost teeth on one occasion on a cog. 3rd gear from memory.
The thing is, when these parts fail, it's usually for a reason.
The reasons can be many - abuse, faulty manufacture or installation or even 'poor / bad' design at the outset! (Engineers never make mistakes?).

How do you know - that the stresses which destroyed the cog (in more than one place) didn't also overstress and bend out of thru the shafts - or overstress the bearings or their housing and so on!

What about the bits of metal that went thru the box, where did they go and what possible damage did they do to other components on the way thru?

Are you equipped to test every single component to know it is still within manufacturers tolerances?

IMHO - the broken cog is the end result of a problem - what you need to eliminate first is the cause of the problem.

You say that the needle roller bearings are fine and thats well & good, but do you know for 100% sure that the alloy housing hasn't stretched? Has the machined out bearing carrier become elongated and allowed the cogs to mis mesh at the wrong angle and hence destroy / break the weaker teeth?

Being an engineer, maybe you can measure - determine these things!

I would heartily recommend that you do, find that causal factor before investing a lot of $ into rebuilding that same transmission.

I'm not an engineer, but I did work for an engineering department for 10 years building and maintaining steel railway line, and in that time saw many many metal fatigue broken rails, some of substantial proportions - some that the ensuing train derailement accidents cost human lives even!

Maybe you can do some ultrasonic flaw detection on the remaining cogs & shafts etc, check them all for runout from true and so on!

That or start with a brand spanking new transmission from the ZF Factory....because somewhere in the one you have on your hands at present is a causal factor...that so far you don't appear to have identified!

Maybe even cast your eye over the engineering design - you've already alluded to the fact the teeth are very small in comparison to all the others!

Ask yourself the question...would the cog have lost it's teeth, if for example you always towed any trailers in direct drive (4th?) gear in the transmissions past history?

It'll be interesting - when you've had good time and opportunity to examine this from all angles, to hear what thoughts you eventually come up with for causal factor.

I for one look forward to your ongoing feedback - maybe we can all learn something vicariously from this!

For what little it's worth - I feel your pain!

Cheers!

 

After thinking about the procedure for an evening, the first thing that I am going to do is to remove the shift handle on the top of the transmission and try there first. It's more toward the rear of the transmission and would IMO provide a better chance of getting a direct view of the OD cluster.

 

I should have said 75w-90 Syn. instead of 70w. IMO it is a much better gear lubricant than ATF. The factory specs ATF to increase fuel mileage W/O concern of bearing/gear life. Sort of built in obsolesence.

Merry Christmas to All!

 

I don't think you will have much of a view there. I just went and looked at my old tranny (I kept it for a spare), and the cover where the shifter goes in is only about 3 inches across. If I remember correctly, it is just a ball below that cover. I will try to go do some postmortem on it, without splitting it, to see where the best access to view is.

on edit:
maybe you will e able to get a mirror into that hole. just about 1 inch on either side of the shift slide.

 

This thread has prompted me to go online and try to find a repair manual for this and I have found some interesting info. This same transmission is used in the corvette, BMW and Chebby (cough-cough) duromax. The BMW specs synthetic 40w-60 oil. The corvette listed 30wt oil too. But the GM vehicles do not use a transmission cooler as Ford does. This unit is used on many vehicles all over the world and is manufactured in Germany.

 

Hmmmm, I didn't know about all of that, but I did know that ZF built the Hindenburg. Yet another reason to get the automatic, IMO.

 

I think our ZF 6 is bigger than a vette.