Hey folks,
Hope someone can help me diagnose what the problem is.
Here are the symptoms:
When accelerating (normally) I hear a knocking sound coming from what I believe to be the area of the transmission.
The rate of kocking increases with vehicle speed.
It happens in all gears under acceleration.
Note the rate of knocking does not change when I change gears (but knocking rate increases with speed)
No noise when coasting in gear
No noise when "engine braking"
No noise when revving engine in neutral or with clutch depressed (while moving or at a standstill)
The knocking starts off slowly at very low speed and increases in frequency
with speed until hat highway speed it is more of vibration than a knock.
The harder the acceleration the louder the knocking.

I have not made any changes to the car recently but I did lightly bump the bottom of the car a few times when driving VERY slowly on a rutted out gravel road (please don’t chastise me for abusing my baby!) I looked under the car and did not see anything out of the ordinary. Anyway I noticed new knocking after this incident


I put in new poly tranny mount about year ago (along with new engine mounts).
I put in a new clutch about 2-3 years ago SLP, with light weight flywheel (and yes I have the rattling when in Neutral everyone complains about)
Car has about 50K Miles on it.

Suspect:
something is out of alignment?
worn u joints (how much play is normal or ok?)
Transmission output shaft ?

Anyone have any thoughts about what this could be?

Thanks folks
Kris

 

Have you really ragged on the car hard recently? And is this a very distinct, metallic knocking sound? Almost turns into a "buzzing" sound once you're up to road speed??

Sounds like the exact same sound my car made about ~1 month ago when 2 teeth sheared off the pinion of my 4.10's. Maybe that's NOT what your car is doing, but a pretty quick and easy check is to jack up the back end, support the car from the frame (so the diff will hang down) and pop the cover off. If there are any teeth missing, they should be stuck to the magnet on the inside of the cover (mine were) but even if not, it won't be hard to spot a broken tooth (or 2, or 3).

For the sake of some lost gear oil, it's a pretty easy "check", and if the gears ARE in fact broken, you don't want to drive around like that too long.

Best of luck.

 

Hey Capn Pete,
When I first read your post I thought, naaaa that's not it, (as the sound really appeard to be coming from the tranny). Well to make a long story short. I had the same problme you did, some teeth were broken. Wierd thing was I had not be beating on her in a while. Anyway glad to know what it is (and thankfull it is not a tranny problem). Thanks for your input!
Kris

 

NOW, the million dollar question is.....

.....do you put back 3.42's (assuming gears were stock? ), or do you put in 4.10's???

 

You know there was a time when I wanted 3.73's but since I do mostly Track events (as in Road Racing circuits) 3.42 are actually fine. And with Gas prices the way they are.... well... I just went back to the 3.42's.
Not a 1/4 mile guy
Kris.

 

That makes sense. Have you raced up at Mosport before? That's where I blew my 4.10's last month (and as well, the 4L60E ). I wasn't on the big track though ... just the little DDT.