Transmission or rear end?

JasonNCJasonNC Posts: 880Expert Adviser
Took the 49 out for a test drive after making a few changes to the engine.  The car ran well except for when I either accelerated rapidly or let off the gas quickly, at which point it the car would lurch and make a loud bumping sound.  I can't tell if the "bump" sound is coming from the rear end or the transmission.  I wonder if the driveshaft is engaging the rear end too hard or if the clutch is slipping.  When decelerating quickly, when the hard thump sound occurred, the car would sway slightly.  Any ideas? 

Comments

  • boothguyboothguy Posts: 107Senior Contributor
    I would check the trans mount and the carrier bearing mount first
  • GlowplugGlowplug Posts: 1,813Expert Adviser
    edited November 3
    Did you look under the car?   The outcome of what you see may point to the problem quickest.  GUESS from afar....the center bearing has has come loose from the mounting insulators, one or both?   
  • JasonNCJasonNC Posts: 880Expert Adviser
    Thanks guys, I'll check it out Monday and let you know....

  • Ken U-TxKen U-Tx Posts: 3,706Senior Contributor
    Did the car veer to left or right when accelerating /decelerating? If so, in addition to the aforemented areas to check, check the rear spring shackles and where they go into the frame for looseness, breakage. Check the rubber front eye bushings of the rear springs, these can be gone. Also check the U-Bolts that hold the leaf spring to the spring pads on the axle, and the rubber isolators, they should be tight but can loosen if the rubber isolators are bad. Also check the Panhard rod (lateral stabilizer bar) rubber bushings. One other thing, check the leaf springs for broken leaves!
  • JasonNCJasonNC Posts: 880Expert Adviser
    Ok guys I have checked the center bearing and the mounting insulators and they are ok.  Ken I really can’t see if the front eye bushings are bad because the cover blocks my view, but my guess is they need to be replaced.   I assume by isolators you are referring to what Wildrick Rubber lists as spring mount bushings #103.  Correct me if I am wrong . Thanks.
  • GeoffGeoff Posts: 3,643Senior Contributor
    Check U-bolts holding the diff to the springs, universal joint nuts,  axle end nuts. 
  • Jon BJon B Posts: 6,952Administrator
    I don't know your level of mechanical expertise, so please don't take offense if you've already checked this, but have you rotated the drive shaft to see how much play there is back at the rear axle?  I am not sure what the acceptable play is, but I would think that if it's too much, you'd get a "thunk" back there when accelerating or decelerating .
  • JasonNCJasonNC Posts: 880Expert Adviser
    Jon B said:
    I don't know your level of mechanical expertise, so please don't take offense if you've already checked this, but have you rotated the drive shaft to see how much play there is back at the rear axle?  I am not sure what the acceptable play is, but I would think that if it's too much, you'd get a "thunk" back there when accelerating or decelerating .
    I have done this and there is quite a bit of play back there.  Is that going to be a problem down the road.  As far a mechanical expertise is concerned, I'm a lawyer by trade and a wanna be shade tree mechanic by night...

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