knocking sound from tranny? (with video)

[Dr Vic]

Hi,

I know this is a very common problem posted on these forums and Ive seen many different answers. Basically there is a knocking sound on acceleration which is worse when turning. I also noticed that even when I put the car in neutral and just let it roll the knocking sound is still present but only softer. The sound also gets softer when the car gets past 3k rpm (seen in video)

This was apparently a newly rebuilt engine. The transmission was fine before the swap but mechanic who screwed me didn't finish the engine swap so I had to finish it myself. So there might have been things that he did wrong that caused all this. I have uploaded a two minute video of car driving around.

The cv shafts have been replaced. The tranny is filled with penzoil synchromesh.

I don't think its rod knock because it doesn't make the sound when i rev the engine in neutral. I have another video (uploading currently) which shows no knocking sound (i think) while revving in neutral.

I have thought of a worn center diff but there is no hesitation when turning (slow turning)
however the car does stall sometimes when backing up. Is there any way to test for a worn center diff?

What do you guys think the problem is?

YouTube - knocking sound while driving

 

[anteversion]

this knock sound in my opinion does not come from the tranny itself, or at least from all the internal components except the two roller bearings that are carrying the front diff. if the sound is not present while the car is not moving and while he is running in neutral, all the spinning components in the tranny are not suspectible to be the problem. Even if you are in neutral, main bearings of the tranny are spinning cause the clutch is engaged and the shafts are spinning.

I have some knocking sound from the tranny of my dsm but as soon as i push the clutch in, all disapeared, wich indicate a worn input shaft bearing.

Your knocking sound looks very similar as a worn cv shaft but by your description of the situation, it should not be the cause of the sound, but it's very knocking like this.

I suggest you to inspect the two front cv shafts for loose on the cv shaft themselves and mostly about if they seems to have some radial play at the section who is entering into the tranny. if it seems to be exagarated, or if the seals are leaking, it might indicate an exagerated bearings wear.

otherwise, look for something rubbing underside of the vehicule, or even the output shaft of the trannywich is entering in the transfer case, might be some very stripped out splines that are spinning on each others ( maybe exagerated but not impossible )

 

[Dr Vic]

so how do i do this? do I just rock the tulip as it enters the transmission? what about a worn center diff? does this sound like it?

 

[heckles]

make sure the small bolt (the one above the transfer case) on the tranny hasnt backed out, and the rest of the bolts. also check the bolts that hold the driver side cv axle to the block. what ever you do, do it soon. you dont want anything to shake loose. good luck

 

[Dr Vic]

Ive actually only used 4 bolts to hold the tranny and engine together. Some of the smaller bolts presumably holding the plate that mounts the starter I was missing. so I skipped out on some of them. do you guys think they're significant? Ok Ill look at that small bolt. I remember that bolt. I didnt understand why there were only those 4 bolts holding the tranny and motor together.

 

[ilco187]

what about the carrier bearing on the driver side bolted to the lower part of the block, by the AC pump it could have came loose, or the driveshaft is loose.

 

[Dr Vic]

I tightened the 2 bolts holding the carrier bearing when I replaced both driveshafts. the sound has not changed even after I changed both axles. so this thing doesnt sound like a worn center diff to any one huh?

 

[ilco187]

i would inspect the external drivetrain components cause i noticed when you turned it went away like something is loose or out of place, at the worst i would say a worn vc, or blown center diff, if it has the 2 spyder gears but i never have blown a diff, till recently and it was welded, but i hear no noise at all from my trans.

 

[Dr Vic]

so how would you test to see whether the vc or center diff is the problem?