knocking sound after engine swap (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

 

[jdodds]

Look at the drivers side axle and make sure its bolted to the engine. I didnt torque the bolts down and they came out and made a similar sound.

 

[Dr Vic]

I torqued them down tight with a 1/2 inch ratchet.

 

[Fast-Orange]

Crank walk? did you check for any play in the shaft?

 

[mindset]

Crank walk? did you check for any play in the shaft?

Ehh don't go there just yet.

How do you know it was rebuilt? Did he show you receipts? Did you torque all the main caps down properly?

Definitely sounds like a bad CV Shaft. Or something in the drivetrain because if it's not knocking while in neutral, there's a drive train problem.

And check tie rod ends and the ball joints.

 

[ilco187]

Crank walk? did you check for any play in the shaft?

crankwalk no its not, i said once on another thread its gotta be something loose,

you did say that when in neutral and you move it you can hear it, my guess is put it in neutral engine off and have a friend push while you check under the car at a slow speed. thats the only way to get a direct point of where its coming from.

 

[Dr Vic]

This is a 6 bolt engine so Im not sure how often crankwalk happens in these motors. I checked the tie rods and ball joints they are all ok. I didnt observe any play on the crank while I was turning manually. Is there another way to check play just by taking out the plastic timing belt cover?

Ill try pushing the car while its off. What else could be loose aside from that small bolt on top of the transfercase?

I torqued down the flywheel bolts to about 90-100 ft/lbs with loctite. I didnt grease the throw out bearing but I did grease the input shaft.

With regards to the engine rebuild. I didnt rebuild the engine myself. The guy that sold it to me said it was recently rebuilt. It had a new head gasket from just inspecting it.

How about a bad center diff or viscous coupling?

 

[tenn-gsx]

Check your driveshaft carrier bearings. The bolts could be loose letting the driveshaft flop arround.

 

[Dr Vic]

Do you mean the two bolts attached to the block? I believe I tightened those down already. How about the bearings in the transmission where the drive shafts go into?

I really think there is something loose in there.

Im gonna pull the transfer case out and check the bolts holding the trans to the engine.

Any more tips on what loose things I should look for?

 

[Burnett03]

It's not rod knock. Get under the car and listen for the noise to pinpoint.. You can use a screwdriver and press it to your ear and hold it against things to try to pick up the sound.

 

[BigSorn]

the bolts holding the driveshaft up.

 

[Dr Vic]

how would a worn front differential sound like? Im asking this because the sound is similar to a worn cv axle and the reason why I swapped the engine was because the front motor mount was broken from the block.

 

[tenn-gsx]

Get under the car and make sure your driveshaft is in good shape. Check the bolts that hold the driveshaft to the car. Check the rubber part of the carrier bearing . Check the U-joints. The fact that the knocking stops at a certain rpm tells me that either your geting enough torque to make things hold still or that the part is spinning fast enough to keep tention on the area that is knocking.


On a side note. You said that you bolted the mount for the axle to the block already. Is the A/C installed? If not then is the a/c compressor bracket still mounted to the car? If the a/c and the a/c mounting bracket are both removed then did you atleast shim the driveshaft mount so that your not puting extreme stress against the shaft?

 

[Dr Vic]

what do you mean shim the drive shaft mount? The a/c and a/c brackets have been installed. I just bolted them straight up. The axle carrier bolt that does not go through the block I put a few washers in because the bolt itself was getting extremely tight as I turned it.

would having the front motor mount not installed properly cause damage to the transmission somehow thats only now becoming apparent after I changed the motor with the front mount securely in place?

 

[tenn-gsx]

ok I was making sure that you didnt bind up the bearing by bolting the axle directly to the block.

 

[tenn-gsx]

You really should get the car on a lift or on 4 jackstands. Then start it up and put it in gear so that you can see and hear the moving parts more easily. If the noise stops when in the air then have someone apply a very small amount of brake so that there is a load on the drivetrain. Im 99% sure that you will be able to see or hear where this noise is coming from this way.

 

[ilco187]

^^^ that's a good idea, do that a report back with the results.

 

[Dr Vic]

yeah i will. so nobody is blaming the center diff, front diff, or viscous coupling?

interesting....

 

[mindset]

yeah i will. so nobody is blaming the center diff, front diff, or viscous coupling?

interesting....

No. I mean if the car is driving and going into gear ok, they why would it be a tranny problem?

 

[Dr Vic]

i dont think the gears are a problem. Ive been reading about stuff on the forums regarding bad center diffs presenting with sounds similar to bad cv axles

 

[lacroixdp]

i dont think the gears are a problem. Ive been reading about stuff on the forums regarding bad center diffs presenting with sounds similar to bad cv axles

My center diff sounded exactly like a bad CV Joint, but it was also accompanied by revving with little to no motion.

 

[Dr Vic]

so how could I tell if its really the center diff vs other things? By the way where do you get the repair kit and how much is it?