TheSamba.com :: View topic

Sat Apr 11, 2009 1:59 pm

Occasionally when I come off the gas in 2nd or 3rd gear or when I downshift and haven't rev matched perfectly there is a loud *POP* noise that emminates from the rear of the Bus. No, it's not backfiring. Sounds like it's coming from the transmission/nosecone area.

Any ideas?

Sat Apr 11, 2009 4:22 pm

How are your axle fulcrum plates? I had bad axles and plates. When I drove around town, if I let off the gas from cruising so the transaxle would slow down the bus, it would make a popping sound. Too much play in the side gears where the axles and fulcrum plates were mushroomed out. Also check transaxle mounts. If those mounts are bad and separated that could cause transaxle movement. Not sure if that would cause popping sounds.

Sat Apr 11, 2009 4:42 pm

Could be a lot of stuff back there. Axle nut torque, mounts, tranny side plates (as mentioned), springplate bushings, springplate bolts loose...

Sat Apr 11, 2009 5:40 pm

Had a similar noise once. After a lot of looking found it was the center of the clutch plate just about to let go.

Sat Apr 11, 2009 10:46 pm

If the fulcrum plates and/or shovel end of the axle(s) were bad (too much play), you would hear a clanking sound when first accelerating in first and second gears. Is that the case?

Sun Apr 12, 2009 12:31 am

No clanking noise. I'm thinking it might be tranny mounts, the fulcrum plates or the axle nuts. Hell, even all of the above.
The rear end does make clunking noise when going over bumps. Anything I should be looking for when examining the tranny mounts and fulcrum plates?

Sun Apr 12, 2009 1:25 am

blitzkrieg59 wrote: No clanking noise. I'm thinking it might be tranny mounts, the fulcrum plates or the axle nuts. Hell, even all of the above.
The rear end does make clunking noise when going over bumps. Anything I should be looking for when examining the tranny mounts and fulcrum plates?

Nah! Drive it 'till it falls apart, then fix it!

Sun Apr 12, 2009 11:24 am

The "normal" things that you would suspect would cause a noise upon acceleration, i.e., worn thrust side of the fulcrum plates and/or shovel end of the axles. Has the front shifting shaft and shift lever been moving up and down? If so, the rubber in the nosecone mount would have split, The first thing that you want to do is examine the three rubber mounts, then see if the bolts for the mounts, carrier, and spring plates are tight. As long as you are looking, see if the coupler is in good shape.
The RGBs/axle tubes and axles have to be removed in order to check out the axles, fulcrum plates, and side gears. A side gear that I removed from two different bus transaxles each had a crack in it, so if you ever remove the side gears, check for cracks and wear on the inside after the fulcrum plates have been removed.

Sun Apr 12, 2009 1:37 pm

Well I could manipulate the popping noise by gassing it then letting off, making the axles twist back and forth between the "speeding the bus up" mode, to "slowing the bus down mode". It ddrove me nuts. When I learned that the axle fulcrum plates and axles were mushroomed out and allowing too much axle movement in the side gears, I replaced them. It wasnt ear deafening loud but oh boy did town driving suck. 1st and second produce the most popping due to the torque. 3rd and 4th have less of the popping cause the engine has less leverage on the axles I think.....not sure but its the same as the jerky affect you have when you are on and off the gas in the lower gears in manual transmission vehicles. The taller 3rd, 4th and 5th if you have that, wont have the sudden lurching. Mine was so bad that people would look at me if I made it pop when driving by them.
If you want a quick check of your axles and plates, try jacking up one of the rear tires and rotating the tire and see how much play is in there. You should have some, but not more than an inch or 2. Ive heard some people tell me they just drove them that way, they didnt care about the popping. Im the kinda guy that thinks to much and this would bother me. Maybe possable chunks of plate, axle going through my transaxle and taking it out? Many things can pop. Loose shock absorbers or broken ones for that matter can pop or clunk.
Got a digital camera that takes video......record the sound...post the video. Sounds help diagnosis, especially when we arent there to hear it.

Sun Apr 12, 2009 3:04 pm

I don't see how it could be caused by worn axle/fulcrum plates if there is no clunking sound when first accelerating in first and second gears. When the bus has gone over a bump there was a clunking sound, which leads me to believe that the transaxle or a shock absorber is loose, at least regarding that sound.
The "popping" sound occurs when letting up on the gas in 2nd or 3rd gears and when downshifting if the layshaft and mainshaft are not synchronized makes me think that the problem could be in the transmission. With a bad synchronizer ring, though, there would be a grinding sound, and one gear not fitting properly into the other could cause it to pop out of gear. A good private dick is needed here.
Because of the "clunking" sound when having gone over bumps, make sure that everything is tight, back there.

Mon Apr 13, 2009 11:18 pm

Yes your right, I didnt have the popping noise when first accelerating in first.....unless I had backed up then put it in first and took off. Yep do check shocks out. I had my front making the popping noise over bumps. I thought it was the front beam making that noise. Well I was close. I just put bilstein shocks on and when I did........no more noise. Loose front shock. It was either loose or the fact that the rubber in one of the ends was degrading.