The inner workings of a 6R140 transmission

[456heinbach]

Sent you a private message.

Thanks

 

[Harusch]

Hi Matt. I found this excellent thread of yours while searching the web for information about a potential problem I might have with my truck’s 6R140 transmission. I know I am reviving an old thread but I am hoping you might be able to answer a few questions. I am working on my 2012 F450 which like the one in your thread was an ambulance. It has just over 90,000 miles and is the original transmission with no transmission service having been done previously. It is rear-wheel drive only with the fixed flange yoke on the output shaft, not the slip yoke. The problem is there is an occasional vibration that you can feel in the floor of the cab, and sometimes even an audible clunking that seems to come from the driveshaft or the rear of the transmission at speeds between 40 to 60 mph. Suspecting the driveshaft was the source of the problem I investigated that first. There is no dents in the shafts and all the U-joints are in good working order. The truck has a three-piece drive shaft with two carrier bearings. The rear carrier was a little worn and sloppy so I replaced it, but that did not eliminate the noise. The front carrier is in good shape and has no slop. But when manipulating the front-most driveshaft I can feel and see movement of the flange yoke on the transmission output shaft, along with a soft clunking noise that might be the louder noise heard at speed when amplified by the rotating energy of the driveshaft. So my question is, how much slop/movement is acceptable for the output shaft? The vehicle service manual does not provide such a spec. From the service manual I see that there is actually two output shaft bearings, an inner and outer. The procedure to replace them calls for the removal of the transmission from the truck and complete disassembly. The seal is not leaking at the output shaft, so if the bearings are going bad they have not caused the seal to wear yet. But if they are going bad, can the rear or outer output shaft bearing be replaced without removing the transmission from the truck? Would I be able to remove the yoke, remove the special spanner nut, and use an internal bearing puller to remove the outer bearing? Your knowledge and help is most appreciated.

 

[clinebarger]

No way to replace the output/case bearing assemblies without first disassembling the unit & removing the output shaft. Does the vibration go away when shifted into Neutral?

 

[Harusch]

Hi Clinebarger. Thanks, I plan to try what you suggest tomorrow. I'll get the truck up to speed and when it starts making the noise shift it into neutral and listen/feel for any change. Another thought I had was to put the rear up on jack stands and then fire it up, put it in gear, and carefully bring it up to "speed" while having my brother observe the output shaft yoke and drive shaft and listen for the noise. I'll also measure exactly how much movement there is with a dial indicator.

 

[Harusch]

Quick update, last weekend was a washout with the remnants of hurricane Ian soaking us here, so I did not do any further road-test investigation. But I did measure the transmission output shaft side-play with my dial indicator. In the east-west orientation I measured .0235". Later on in the week in hindsight I realized I should have also measured the movement north to south for comparison, so I'll redo the measurements tomorrow. Can someone tell me if this spec is published in any of the rebuilding manuals? I have searched the interwebs all week and have not found it. This is my first truck with a "newer" transmission like the 6R140, and all of my other vehicles have output shaft extension housings with bushings for slip-yokes so I have no basis of comparison to know what is normal for these Torrington needle bearings.
Also upon taking off the front driveshaft segment I found that the front carrier bearing was a little dry and crunchy, so I ordered a new replacement and will put that on tomorrow as well. After it is all reassembled I will take the truck on a drive to try and narrow down the conditions that make the clunking noise occur.

 

[Dave Hess]

Worn down to the metal zero friction material left on half of the friction plates in that set. Forward, direct, and low/reverse were worn beyond maximum limits and the overdrive was worn 5 times max limit. I am very impressed how well the TCM adapted to the wear. This particular clutch (overdrive) has too little surface area compared the others in the transmission. There is an aftemarket clutch drum that has 50% more holding power from increased clutch count but requires a billet intermediate shaft and billet input shaft (which also acts as overdrive drum) to a tune of 1500$. Not a reasonable cost for a municipality. This truck is a F450 rescue with a 6.7 powerstroke. Just over 100k miles. It's gstting a full overhaul. There are several updated hard parts too ford has made over the years.

This transmission is not bad to rebuild. Some special tools are required specific to this unit. They are also heavy 325lbs dry. The input assembly alone all together weighs 80 lbs . Its 4 pic up from bottom on the left.

Nice photos. How much does it cost to rebuild this trans for customer ?