Posted by Keith in Washington on Wednesday, August 15, 2001 at 4:42PM :
Dave or anyone else. The transmission in my Carryall developed some bearing?? noises on a 200 mile trip. This is an SM420 transmission with PTO. It has 4000 mile on it since all gears, bearings, shafts i.e. everything was replaced with new.
Here are the symptoms. Can you give me a clue as to what is happening and am I thinking correctly.
1) With the engine running, trans is in neutral and the clutch depressed there are no noises. Truck is not moving.
2) Engine running, transmission in neutral and clutch engaged there is a rumbling sound.
3) Driving down the road in any gear. Slight rumble to whining sound. Noise lease noticeable in 4th gear. With the other noises in the truck it is hard to hear the noise in 4 gear. Noise is more noticeable in lower gears. You have to listen to hear the noise above the normal truck noise.
4) Coasting down road with transmission in gear and clutch depressed. 2nd gear very loud bearing noise. 3rd gear loud bearing noise less than that if truck was in 2nd gear. 4th gear slight bearing noise. Noise in 2nd gear is very loud and sound like something should fall out at any time.You could hear it with ear plugs on. I do not even need to get it in gear before the noises start. All I have to do is move the shifter far enough so that the synchros are engaged and get the input shaft/ lower gear cluster spinning.
My guess is that the bearing on the input shaft is gone or the bearings that carry the counter shaft (lower gear cluster) have gone out. Or possibly the needle bearings between the input and output shafts. It also seems to be related to the amount of torque that the shafts are under. Ie the most noise occurrs in lower gears which would put the most torque between the lower cluster and the input shaft.
I will be taking the trans out tonight and would like to get it back to the place that put it together by Friday.
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