HELP--Driveshaft auto-brake area throbbing vibration
1996 P30 chassis - 36 ft 1 slide - ~17k chassis rating - 70k miles
I went to Oregon last yr from mid Calif (SJ area), U-joint was bad, did not know it, finally heard a clunking when going into gear - found out that a sign of bad u-joint (and it was bad).
Replaced it, making sure to keep drive shafts 'in sync' (same orientation as orig - hard to mess up except can be out 180 degrees), seemed ok while in oregon, did not go far between campgrounds but full speed, all was ok, 4 trips of ~60 mi.
Coming down from oregon in Dec to N. calif, all seemed ok too, but when going from Alexander valley (wine country lovely area) area south to 100mi S of San Jose, 200mi trip i noticed a smell-like burning brake going ~100+ mile into trip, stopped to check out, did not find anything, kept going.
Once at destination, I worked on the auto brake (thinking not fully releasing?), thinking that was what caused smell, seemed ok. Ordered new brake and cable - oregon humidity makes everything rust eventually.
Went ~50mi to new campground, had to leave after 3 days due to flooding, still no throbbing issues - ~50mi.
(btw the auto brake is like a drum on back of trans connected via a spline shaft, actual brake sys mounted to plate on back of trans, cable activates the drum brake to squeeze the brake into spinning drum/drive shaft used only for parking-this is the P30 auto brake pump/solenoid leak issue - made it purely manual brake).
Got parts and played around with new brake, old cable too short (had shortened ~1" it get tighter/stronger manual park brake) for new brake so put old back on.
Went to alternate campground, ~10mi, and a strange throbbing (FIRST occurrence) was coming from the park brake area (just behind transmission connected to drive shaft), so had to slow to ~35mph !!! Much like a wheel severely out of balance but sound/throbbing not from a wheel area - from behind 'dog house' - tire pressure was good too.
when I went back to campground ~10mi same throbbing, I thought the park brake the issue so removed it completely (just used drum to connect the driveshaft - a necessity!), same throbbing next trip.
So I just replaced the u-joint again w/ a better quality spicer (2x price) and will see but suspect throbbing will not be gone.
Before replacing u-joint, ran engine in gear w/o driveshaft, to different speeds/gears (up to 70mph or so!!), no real unexpected vibrations (throbbing always only starts after a ~3-4mi miles (thermal issue?) - so not a good test really - may need loading/heat buildup)
My fear is that somehow the splined shaft from transmission that connects auto brake drum to drive shaft may be bent?, but how, seems ONLY an issue once I messed with things, it only makes sense that the bad u-joint caused it but then why not show up until now - 800+ mi later ?
But I really do not think this, have carefully checked things, made sure all drive shaft parts in line looking from trans and in sync, drive shaft has little angle, greatest is from trans to #2 joint/mount area - ~1 degree maybe less.
Drive shaft has 3 parts, 4 u-joints, 1 keyed splined joint, 2 mid mounts w/ non rubber mount u-joint bearings.
If still throbbing on next short 10mi trip, will disconnect driveshaft again, run engine/trans in gear, set the cruise control to 40mph in high gear, crawl under and look to see if any shaking of auto brake drum - need some ideas and maybe more info too.
Will also crawl under when getting to new destination to check thermal issues.
If I can't fix I can't leave here (time to go North again) OR will have to resort to pro work & huge inconvenience - which may not be any better than MY unprofessional DIY skills but lots of $$ !!
HELP ! ANY ideas ?
PS: fully greased new and all 4 other u-joints/spline joints.
I went to Oregon last yr from mid Calif (SJ area), U-joint was bad, did not know it, finally heard a clunking when going into gear - found out that a sign of bad u-joint (and it was bad).
Replaced it, making sure to keep drive shafts 'in sync' (same orientation as orig - hard to mess up except can be out 180 degrees), seemed ok while in oregon, did not go far between campgrounds but full speed, all was ok, 4 trips of ~60 mi.
Coming down from oregon in Dec to N. calif, all seemed ok too, but when going from Alexander valley (wine country lovely area) area south to 100mi S of San Jose, 200mi trip i noticed a smell-like burning brake going ~100+ mile into trip, stopped to check out, did not find anything, kept going.
Once at destination, I worked on the auto brake (thinking not fully releasing?), thinking that was what caused smell, seemed ok. Ordered new brake and cable - oregon humidity makes everything rust eventually.
Went ~50mi to new campground, had to leave after 3 days due to flooding, still no throbbing issues - ~50mi.
(btw the auto brake is like a drum on back of trans connected via a spline shaft, actual brake sys mounted to plate on back of trans, cable activates the drum brake to squeeze the brake into spinning drum/drive shaft used only for parking-this is the P30 auto brake pump/solenoid leak issue - made it purely manual brake).
Got parts and played around with new brake, old cable too short (had shortened ~1" it get tighter/stronger manual park brake) for new brake so put old back on.
Went to alternate campground, ~10mi, and a strange throbbing (FIRST occurrence) was coming from the park brake area (just behind transmission connected to drive shaft), so had to slow to ~35mph !!! Much like a wheel severely out of balance but sound/throbbing not from a wheel area - from behind 'dog house' - tire pressure was good too.
when I went back to campground ~10mi same throbbing, I thought the park brake the issue so removed it completely (just used drum to connect the driveshaft - a necessity!), same throbbing next trip.
So I just replaced the u-joint again w/ a better quality spicer (2x price) and will see but suspect throbbing will not be gone.
Before replacing u-joint, ran engine in gear w/o driveshaft, to different speeds/gears (up to 70mph or so!!), no real unexpected vibrations (throbbing always only starts after a ~3-4mi miles (thermal issue?) - so not a good test really - may need loading/heat buildup)
My fear is that somehow the splined shaft from transmission that connects auto brake drum to drive shaft may be bent?, but how, seems ONLY an issue once I messed with things, it only makes sense that the bad u-joint caused it but then why not show up until now - 800+ mi later ?
But I really do not think this, have carefully checked things, made sure all drive shaft parts in line looking from trans and in sync, drive shaft has little angle, greatest is from trans to #2 joint/mount area - ~1 degree maybe less.
Drive shaft has 3 parts, 4 u-joints, 1 keyed splined joint, 2 mid mounts w/ non rubber mount u-joint bearings.
If still throbbing on next short 10mi trip, will disconnect driveshaft again, run engine/trans in gear, set the cruise control to 40mph in high gear, crawl under and look to see if any shaking of auto brake drum - need some ideas and maybe more info too.
Will also crawl under when getting to new destination to check thermal issues.
If I can't fix I can't leave here (time to go North again) OR will have to resort to pro work & huge inconvenience - which may not be any better than MY unprofessional DIY skills but lots of $$ !!
HELP ! ANY ideas ?
PS: fully greased new and all 4 other u-joints/spline joints.
