m35 transmission noise..

[OkieM1008morrison]

My latest project thanks to the Oklahoma forestry department is a 71 M35 that has 29,354 miles runs great and I got it for almost nothing in my book. the problem is a small knock that gets worse with speed, but it only does it in 1st gear in high and low side of the transfer case. as soon as I put it through the other gears it makes no knocking noise whatsoever, and acts normal. I checked both fluid levels on the tranny and transfer case, they are good. pulled the access panels so I could drive and listen and feel where the knock mite be coming from. after driving it a few feet I could hear it clearly coming from the transmission. but only in first gear, as soon as I shift into 2nd no noise at all, or any of the other gears. the transmission is tight and does not move excessively when driving. I decided to pull the top of the transmission to see if there was anything that was obviously out of place or broken, nothing seemed obviously wrong, any ideas? suggestions?

 

[cattlerepairman]

Have you checked the jack shaft bolts (short drive shaft between tranny and transfer case)? They have a tendency to come loose and make all sorts of strange noise at lower shaft rpm.

 

[gringeltaube]

When starting from a full stop with engine below idle speed, does it knock say 6-7 times per second, or just 1-2 /sec.?

Did you get to inspect this one, the 1st counter-gear? It only has 13 teeth (from factory at least...)



G.

 

[OkieM1008morrison]

I did check the jack shaft bolts, one was just a tad loose. the U joints are tight also, when starting from a full stop, it does not knock or make any noise until you start moving it starts knocking 1-2 times per second and gets worse and knocks harder with the increase in rpm's, as soon as I shift into second it immediately stops and sounds as it should. I still have the truck opened up in the driveway I will check the 1st counter gear, I hope it has 13 teeth...

 

[gringeltaube]

Put in 1st gear, with clutch fully engaged and engine pulling @ say 600 rpm, it should be 2 knocks per second but only if... the large sliding gear (45T) had one (or more) teeth missing. Or perhaps something embedded in between two teeth? But you said you checked already and didn't see anything abnormal, there?

Really the most frequent case is that you find the much smaller (13T) counter-gear with its teeth severely chipped to half the original width or worse, and/or completely missing some. But then the knocking would be much faster, 7-8 times/second.


Tell us what you found and shoot some close-ups.


G.

 

[OkieM1008morrison]

when I opened up the transmission I turned the closest gear on the top towards the rear of the truck, as I rotated it I found a tooth completely gone, and the rest of the teeth on that gear were very worn as well. the corresponding gears below [the gear that has 13 teeth ] was very worn as well but not missing any teeth. not shure what my plan of action is yet, I have a parts truck handy that has a good transmission so that is an option. this would be my first tranny swap, I guess I need to do some research on here. I have a forklift standing by if need be.

 

[gimpyrobb]

Shift trans so the stub shaft out the back "sucks in".
Pull top off trans.
Loosen all bolts holding it in place.
Bolt a chain across the top of trans.
Put bar from front window to the back of the cab.
Run a come a long from bar to chain on trans.
Take weight off trans bolts and pull bolts.
Pull trans from motor and lower to ground.

Install replacement.

 

[frodobaggins]

Thanks gimp, got to do this myself soon.

Shift trans so the stub shaft out the back "sucks in".
Pull top off trans.
Loosen all bolts holding it in place.
Bolt a chain across the top of trans.
Put bar from front window to the back of the cab.
Run a come a long from bar to chain on trans.
Take weight off trans bolts and pull bolts.
Pull trans from motor and lower to ground.

Install replacement.

 

[jetman10]

I don't know if this is the correct place for this, but I have a problem with my deuce not having any high range . All 5 gears are quiet in low range, trans shifts good but nothing in high range . I bought it like this but never had it on the road while bobbing it and adding a bed . No noises like chipped teeth or anything . I haven't checked it out fully but the lever clicks good going from low to high . I'm going to check the linkage first . Is it possible that a shift fork broke and just fell to the bottom ? Plus, Can I take the floor panel up and get access to the top cover if there is one ? Maybe I should drain the oil and see what falls out ? I have 2 thick TM books I had made, but they don't cover the T-case . I've read 100s of threads in here and learned a lot so far. Thanks .

 

[gimpyrobb]

I'd pull the sheet metal on the floor and check the linkage first.
You will then have access to all that stuff if it isn't the linkage. If you have all gears in low range, I'd suspect the T-case before the transmission.

No mention of any reverse issues?

 

[JDToumanian]

Shift trans so the stub shaft out the back "sucks in".
Pull top off trans.
Loosen all bolts holding it in place.
Bolt a chain across the top of trans.
Put bar from front window to the back of the cab.
Run a come a long from bar to chain on trans.
Take weight off trans bolts and pull bolts.
Pull trans from motor and lower to ground.

Install replacement.

Instead of the come-along, I use one of the cute little chain hoists for changing tires that come with the 900 series 5-tons...

 

[Jeepsinker]

Agree with the chain hoist! Definitely the transfer case, unless you have a Sprague case, then it could be a linkage adjustment issue. Does your truck have an air shift front axle engagement?