Just pulled M47; It had a weird noise, a grinding in first and second. Thought it was a throwout bearing but it but it was good. . Backing up here.

I repaired (M47) reverse gear about a month ago. After I repaired it (replaced the small reverse gear), I reinstalled it and it performed great but developed and grinding noise going down the road. Just in first 2 gears; at a certain RPM. The tranny shifts great. I popped the cover off of it tonight but all seems good. Now Im stumped. Pilot bearing good. Carrier bearing good. Really need some help. I have an auto but hate to install it. But might be forced to.

 

normally something like that would be shim related or possibly gearing direction. Some gears only go in one way.

Tear down and re do, try again I guess

Any metal in the oil?

 

If it was a gear noise it would only do it in that gear. My first instinct is to see if the 1 and 2 gears are on the same shaft. That would lead me to believe it is on of the bearings on either end of the shaft that supports it in the case. Maybe a shim got left behind when the gear was replaced?

 

no metal in the oil. I pulled the tranny and popped the cover off. Everything looks good. Im gonna replace the carrier bearing. Its seems a little rough but have a had time believing that is it. Im gonna pull tranny apart in couple of days. It has me stumped.
The noise is briefly in 1st gear and pretty frequent in 2nd gear. Sound like a grinding noise. Only does it at a certain rpm. If I let off the gas, it goes away.If I dont find anything in the tranny and it still does it, Ill record the noise and try and post it. Thanks

 

all the gears are always engaged, its just the gear thats selected is 'locked' to its shaft via the synchro, the others are free spinning.

 

Yes that's true but when they are loaded is when you are getting the noise. If it is louder in 2nd gear then it's possibly the bearing closer to that gear set.

 

I replace ujoints and carrier bearing. They needed replaced was hoping that would fix it but knew it probably would not. Just drove it, no change. So, which bearing is closest to 2nd gear? It does it worse when I am in 2nd and have a medium load or accelerating going down hill. My only other thought or quesiton is? Could the guibo be installed wrong?I have bolts facing the right way according to the arrows. But, could I have the wrong with the driveshaft/transmission cordination?

 

did you seperate the two halves of the drive shaft at the spline, and if so, did you mark them so you reassembled them aligned the same way? I ask, because that assembly is balanced in the factory.

what condition is the driveshaft support bearing and the rubber carrier it sits in ?

 

yes i did mark them and also found the factory markings. I replaced the driveshaft support bearing and the rubber carrier and the spring today. With no results. I really appreciate you guys helping me, which I could have you drive it.

 

I don't know the specifics on that trans. I'm just doing a general diagnosis. I wish I could drive it too then I'm sure i'd know the problem but so hard to tell like this.

 

Maybe I can have my son record it and put it on youtube. Then I will post the link. Thanks for help. The trans shifts great. just makes a rattle off and on in mainly second. I figured I would find metal shaving on drain plug. But it looked good. Its got me stumped.

 

I pulled the trans. I do see the input shaft looks bent. When I spin the tranny by hand I can see a wobble to it. I dont have a dial indicator but plan to get one and check the run out. Thinking back when I replace my pilot bearing I thought it looked shot but it had 180000 miles on it?

 

only way I know for an input shaft to bend is if it was bent during installation or removal

 

yes, i did have a heck of a time getting it in. So, man up, I probably bent it some how. Learned my lesson to take my time and get the car up high enough to move around. Guess I will go lookin for an input shaft. I installed another m47 that was sold to me cheap but they said it made some noise. I replaced input shaft bearing on it and its doing fine. Thanks for the help.

 

finally got a m47 that is quiet and operates properly. Thanks for all the help. Wife is gonna let me keep it. I think m47 are getting harder to find in good shape.