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Knocking sound front left in left turns

dutchjeep

NAXJA Forum User
Hi All,

Lately I noticed a knocking sound on the front left (my estimate in locating the sound) when taking a sharp left turn, in particular under power (but in 2WD). You also feel the knocking in the car (through the frame or steering wheel, not sure).

It is very clear for instance when accelerating onto a road while turning sharply to the left. Or accelerating out off of a sharp left turn (twisty road, not highway type curvature).

Since there is no power directly to the front wheels in 2wd, my first guess was that the fact that it's worse under power is due to the body lean. However, on the other hand, if I don't put power on, I don't hear anything. So then I thought perhaps loose motor mounts (I did replace broken motor mounts about 6 months ago and the noise started a few moths after that), but I've just tightened them and that didn't do much (they were not very loose either). So now I don't know anymore.

Any suggestions? Any thoughts appreciated!
 
Sounds like a bad/frozen ujoint on the left front axle.
 
Yes, that sounds like it may be it (didn't think of that). How do I test the U-joint for wear or damage? If bad, is that easy to fix myself? Thanks for the input!
 
I'd check transmission mounts. If it's only there under power (that will torque the driveline), that would be my best guess. I've also experienced some knocking under power...If I remember correctly...it was transmission mounts. It happened in 2wd, and was less in 4wd.
 
Will check the transmission mounts. Would that be consistent with that it starts knocking in left corners? I guess if it's loose it may be hard to tell when it starts to knock/vibrate. Anyway, I'll check it out tomorrow morning.

Can anyone tell me how I can best check the U-joints for functionality/play/wear/damage?

Thanks for the input!
 
When it knocks is it one knock then done for the episode or does it knock-knock-knock so long as you're in the turn?
 
Mine was making a popping/knocking sound during turns. I replaced all the control arm bushings and it fixed the problem.
 
I will listen to old_man:). That makes a lot of sense to me. Again, can anyone give me an idea on how I check on wear on the u-joints? My limited mechanical understanding derives from motorcycles so drive shafts and u-joints i know nothing about:). But i will give it a go and replace what is needed if worn. Just want to make sure I'm pulling out that what needs pulling out.

J_worth, the sound continues, so it is knock-knock-knock while on the throttle in a left turn (so it's more a rattle/knock, if that makes any sense). As soon as I come off the throttle, or go straight again, it stops. I noticed that the same sound/knock is sometimes there on a cold (rough) start. So I am not yet ruling out tranny mounts either, but haven't had time today to inspect (will have time tomorrow and report back).
 
A loose axle U joint is pretty easy to diagnose. Point the tires straight forward (or near that) and put the tranny or TC in neutral (tires chocked of course). Crawl under the front end with a rubber glove (optional) and try turning the axle shaft by hand. If there is ANY movement within the U joint, the rollers in the cap(s) are worn out. It is more difficult to diagnose a set of bound rollers within a cap. You can turn the wheel to the side where you hear the noise and try to rotate the shaft. You should be able to feel the bind as the axle tries to rotate the bound rollers and cap. Or, you can drive it another hundred miles and the bound rollers will become loose and fail the first test.
 
Ok, did the u-joint check as described by MoFo, but can't seem to find any play whatsoever (straight and with wheels turned). Not sure if that means they're ok or not. I still believe they would be very likely candidates for the sound. I've been driving around with this sound for about 1000 miles and although it seems to very slowly get progressively worse, it does not seem to get worse rapidly. How much of a job is it just to replace the u-joints, just to cross them out?

The tranny mount I can't really tell whether good or bad, but it's old (20 years) and has seen some miles, so I'll just replace that today to get that out of the equation.

Any thoughts on other tests on the u-joints I could do before pulling it apart?
 
Haha, yes and no. Yes, I did replace my steering shaft the other day (last week) with that massive piece of steel that Borgeson produces. But the issues where there before already (I'm glad:)). Also, I didn't really mess with the steering box, just replaced the shaft.

Just picked up the tranny mount, will go ahead and put that one in later today. Don't expect much of that operation, but it's good to do anyway and eliminate that one.
 
It turned out to be the tranny mount. Replaced that and sound is gone. The old one had gone all soft.

Of course, just before I replaced the mount, my exhaust manifold decided to crack (again). I had replaced the exhaust manifold last year (less than 10K miles ago). Can this cracking be due to the bad transmission mount (can that cause extra stresses on the exhaust?)? (the motor mounts were replaced when I put on the replacement exhaust manifold last year).

Anyway, just wanted to let you guys know what I found. Thanks for thinking along!
 
had the same issue in my wifes 98 classic. noise when turning ..been happening for a few months. well today i was making a run to the local autoparts store to get a caliper for my 2 door and BANG noise when turning..long story short...front spider gears busted in frt diff???
pulled the axles and front drive shaft and 2wd for now...
 
I'm assuming that when you say pulled the axles you mean that you broke them at the U-joints and put the stubs back in... yes...? otherwise my understanding is that the hubs/bearings are not long for this world
 
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