Only when cruising, an "on the gas", "off the gas", "on the gas" clunking from the DL
10-12-2012, 07:51 AM
#1
Only when cruising, an "on the gas", "off the gas", "on the gas" clunking from the DL When I am cruising at only higher speeds like on the interstate, I get some annoying clunks from underneath if you let off the gas, then tap the gas, let off the gas etc. It is also extremely noticable when on cruise control and you start to descend down a hill.
It seems to happen when the driveline goes "slack" meaning no accelarating force or decellarating force is being applied to the rear. Also seems to happen when you just begin to "coast" a bit.
It is absolutely smooth as silk anytime force is being applied to the drive line which means the relatively new PST DS should be balanced and the DL angles should set correctly. Also the 9" rear is set up properly and is dead quiet so there should not be any slack in the gears. Lastly the T56 has recently been rebuilt and its good and tight and all mounts are good too.
So what the Hell is doing this?
Could the slip yoke be a bit sloppy and be fluttering around when force is not being applied through it like when coasting? Sure acts like something is loose.
It seems to happen when the driveline goes "slack" meaning no accelarating force or decellarating force is being applied to the rear. Also seems to happen when you just begin to "coast" a bit.
It is absolutely smooth as silk anytime force is being applied to the drive line which means the relatively new PST DS should be balanced and the DL angles should set correctly. Also the 9" rear is set up properly and is dead quiet so there should not be any slack in the gears. Lastly the T56 has recently been rebuilt and its good and tight and all mounts are good too.
So what the Hell is doing this?
Could the slip yoke be a bit sloppy and be fluttering around when force is not being applied through it like when coasting? Sure acts like something is loose.
10-12-2012, 10:16 AM
#2
Staging Lane
Join Date: Mar 2011
Location: Warshington
Posts: 83
Likes: 0
Received 0 Likes
on
0 Posts
What kind of rear suspension do you have? Poly or rod ends? What kind of torque mount do you have? Chassis or tranny mounted? Blown torque bushing or lca bushings?
10-12-2012, 10:57 AM
#3
ANother symptom if you are going maybe 80MPH and simply push the clutch in, I get a small vibe. Let the clutch out, the vibe is gone. Just seems like something sloppy or slack in the driveline.
10-13-2012, 09:34 AM
#4
TECH Enthusiast
Join Date: Jul 2007
Location: Central,NJ
Posts: 563
Likes: 0
Received 0 Likes
on
0 Posts
It could be a u-joint cap getting tight, make sure the u-bolts are not overtightend on the pinion yoke.
More than likely though its a drivline angle issue. I had a similar issue, the total DL angle was a little excessive but would not present an issue untill the power flow went slack. The MWC TA is mounted in the second hole from the bottom because the ride height would not allow me to go to the third hole up, the trans was down 2.8* and the pinion was up 1.0* with the TA adjuster near fully bottomed out. I completly bottomed the TA adjuster and the pinion got to 1.5* up for a total DL angle of -1.3* I wanted it to be -.5* to -1.0* but cannot get it there with out shimming the trans up. That 1/2 degree of change made a huge difference though, the joint speed difference is much closer, the DL is much quiter and accel feels smoother/quicker.
More than likely though its a drivline angle issue. I had a similar issue, the total DL angle was a little excessive but would not present an issue untill the power flow went slack. The MWC TA is mounted in the second hole from the bottom because the ride height would not allow me to go to the third hole up, the trans was down 2.8* and the pinion was up 1.0* with the TA adjuster near fully bottomed out. I completly bottomed the TA adjuster and the pinion got to 1.5* up for a total DL angle of -1.3* I wanted it to be -.5* to -1.0* but cannot get it there with out shimming the trans up. That 1/2 degree of change made a huge difference though, the joint speed difference is much closer, the DL is much quiter and accel feels smoother/quicker.
