84 4x4, Drivetrain knock on acceleration

[jonlittleford]

Maybe someone can help me get to the bottom of this...

 

Car: 84 GL 4 spd 4x4 wagon with 140,000 miles, swapped 140,000 mile engine from 84 GL automatic.

 

Symptom: Acceleration knock, 4 CV axles & 2 rear axles in 1 1/2 year, 6500 miles.

 

History: I bought a nice car with a bad engine about 2 years ago. Had the good hydro lifter engine swapped in. Shortly after, when this knock first appeared, I had both CV axles replaced, along with the rear drive side axle. Drove to Austin & back on what turned out to be bad new-used tires. Replaced tires after trip (now I know). Replaced pass CV axle again 10 months later.

 

I have a repeating knock/grinding grumble coming from somewhere in the drivetrain. Its worse under heavy and/or uphill acceleration, and quieter but still present in 4wd. This (at least I think it's the same knock) was present after the engine swap and a local jobber replaced a cv axle, and then the cv axle on the other side. The sound was gone. Then less than a year later another cv axle was replaced for the same knock (barely still under warranty.) I know the aftermarket cv axles aren't what they used to be, but really? 4 new axles in a year and a half? 5000 of the 6500 miles was the road trip to Austin and back. Also, there isn't the characteristic knock on tight corners, only under acceleration. Although it eventually knocked on corners as well as under acceleration the first time around.

 

I can feel it through my seat and feet, so I'm pretty certain this is from the transaxle on out, and not the engine (which runs great: 30+ mpg hwy, 120psi compression on #2 and 150+ on the others).

 

Also, I felt about 10 degrees of play in the rear pass axle, and replaced it on Saturday, no relief- which makes sense since the back half is disengaged in 2wd.

 

Have I been really unlucky with CV axles (if so can somebody recommend a company or source?), or is there a different problem that's wearing them out so fast?

 

Any advice is appreciated!

[Petersubaru]

a lack of sufficient grease or play or both will cause the cv axle to knock under acceleration on the straight away..you could add some grease useing the needle attached to a grease gun...

[FlatFourFrenchy]

Believe it or not, my axle rebuilder always recommends checking and cleaning the body grounds. If they are not good system will use the engine ground via the axles causing arcing in the joints causing premature joint failure. just a thought.