Sunday, May 30, 2010

Saab V4 Transmission Rebuild - Got Mud?

A customer shipped us a Saab V4 transmission for a rebuild, so I dug into last week, It looked straightforward enough, but when I drained what laughingly passed for oil in the unit, the picture changed. “Swamp Mud” was a charitable description of the stuff, a thick, brown ooze that really didn’t even want to run out the drain hole. The oily yuk suggested that the ‘box’ had been “under water” for a while. It’s consistency was that of a mix of 140 weight hypoid differential oil and water.

I was thinking, as I took the unit apart, about the several needle bearings between shafts and gears in this transmission, and how thick, heavy oil [never mind swamp mud] just cannot lube these little buggers right. It takes 75 or 80 weight high pressure gear oil to keep the needles alive, and a smart owner will use a high quality SYNTHETIC gear oil.

Things began to “fall apart” when I pressed the shafts out of the gear case. Needle bearings fell apart, and the main and counter shafts were scored and burned, indicating a lack of lubricant. The fourth speed gear on the main shaft had deep grooves cut across its bearing surface, indicating that the needle bearings that live there had been deprived of oil for some time.

Second gear on the countershaft had significant RUST PITTING on about a quarter of adjacent teeth, indicating that those teeth had indeed been immersed in water. Several other gears, including the big, spendy ones on the pinion shaft, had suffered similar rust pitting.

Notice the case hardening wearing off this main shaft

Significant lack of lubrication led to heat related wear

Needle bearing lacking several needles

Deep grooves cut across the bearing face on this 4th gear

Extreme amounts of rust on this 2nd gear

A little late to blame anyone, I suppose, but one way or the other, about 90% of THIS Saab V4 transmission was junk.


No comments:

Post a Comment

Note: Only a member of this blog may post a comment.