• Welcome to the new NAXJA Forum! If your password does not work, please use "Forgot your password?" link on the log-in page. Please feel free to reach out to [email protected] if we can provide any assistance.

Rattle under load?

M

MJCfromCT

NAXJA Forum User
Location
CT
I've been trying to pinpoint a longstanding issue I've had with my XJ, I tried searching but couldn't find much.

I have a 93 Sport 2DR 4WD, 4.0L, Automatic. Whenever it shifts into overdrive (right around 45mph it seems), I'll notice a rattle if I am driving under a load (attempting to maintain 50mph while going up a hill, for example). As best I can describe it, it sounds like a loose piece of metal rattling around. If I am driving on a flat, level surface, I can be going 60 or 65 and not notice it at all, but once a load is applied I can hear it. Sometimes its a slight rattle, other times it is very noticeable, it seems to depend on the both the speed and applied load. Sometimes it seems that the lower the RPM in OD and the higher the load, the higher the rattle sound.

Any ideas where I could start looking for the problem?

P.S.: One thing I have noticed is that one of the clamps on the driver side leaf spring set is loose and is can move around, but I wouldn't think that would cause the rattle I'm noticing, as I only notice it under load in OD.
 
Alright, I've got a trip coming up Saturday, I'll buy some premium gas and let you know how it goes. This'll be interesting, I've never bought anything but regular. :shocked:
 
it does sound like spark knock. the chambers might just be all carboned up, try seafoaming it real good. the mopar combustion chamber cleaner is good stuff too.
 
MJCfromCT said:
I've been trying to pinpoint a longstanding issue I've had with my XJ, I tried searching but couldn't find much.

I have a 93 Sport 2DR 4WD, 4.0L, Automatic. Whenever it shifts into overdrive (right around 45mph it seems), I'll notice a rattle if I am driving under a load (attempting to maintain 50mph while going up a hill, for example). As best I can describe it, it sounds like a loose piece of metal rattling around. If I am driving on a flat, level surface, I can be going 60 or 65 and not notice it at all, but once a load is applied I can hear it. Sometimes its a slight rattle, other times it is very noticeable, it seems to depend on the both the speed and applied load. Sometimes it seems that the lower the RPM in OD and the higher the load, the higher the rattle sound.

Any ideas where I could start looking for the problem?

P.S.: One thing I have noticed is that one of the clamps on the driver side leaf spring set is loose and is can move around, but I wouldn't think that would cause the rattle I'm noticing, as I only notice it under load in OD.
Click to expand...


is it coming form the underneath side of the rig or from the engine bay or? my 87 does the same thing and im betting that my rear driveshaft u joints are shot. let me ask you this: in neautral, dose it still rattle?
 
I get something like that, but I would describe it more like a tick than a rattle. I am assuming it is a lifter. It didn't go away using Marvelous Mystery Oil. So I ordered some auto-rx--I hear great things about it. I guess seafoam would be a quiker way to deal with it.

If this doesn't work, I might just live with it since I really don't feel any lack of power.
 
MJCfromCT said:
I dont think it does. As far as I know it only does it in OD under a load.
Click to expand...

that's what makes me lean towards u joints. If it was a motor problem it would do it all the time reagrdless of what gear. have the u joints inspected. I bet thats your problem and good luck. :)
 
So you would suspect a U-joint issue even if the rattle does not occur in any other gear other than OD, and in any other driving condition other than under a load in OD?

Is there a procedure to visually inspect U-joints? I don't have any experience doing so.
 
I doubt it's your U joints. They would be vibrating and grinding at all speeds. Most likely your engine, as when it's in OD it has a higher load. Have you checked your exhaust? Could be your cat.
 
Thanks for the reply,

I haven't checked the exhaust, should I just be looking for excessive play in any of the exhaust components?
 
Sounds just like the ping you get with bad gas or low octane gas Do this put good gas from cheverone in it take it for a drive the noise you hear will most likely go away. IF not suck seafoam through the intake after the TB a vacume line someware will do the trick. replace the spark plugs as this has a tendency to glaze them. and put mid grade in, you can try regular but the ping will probably come back. U joints will be an issue in all gears and will have a nast fibration when bad. If you must check them.Put blocks under the tires put the truck in nutral go unger the truck and move the driveline up and down and side to side if the u joint is moving on itself they are bad if they are tight no problems. in most cases the sound you have described is ping with gas prices on the rise it may be somthing you'll just want to life with.Hope that helps
 
jk333 said:
that's what makes me lean towards u joints. If it was a motor problem it would do it all the time reagrdless of what gear. have the u joints inspected. I bet thats your problem and good luck. :)
Click to expand...
I disagree. A combustion knock under load can not usually be duplicated at idle.
 
The first thing that comes to my mind whenever somebody uses the word "rattle" is the catalytic converter. Classic symptom really. I would perform a close inspection of your entire exhaust as already mentioned by mattbred. Another thing you can do which would be more conclusive is to disconnect the cat for a test run and see if that makes any difference. Simple stuff first. Let us know what you find...
 
A bit of an update:

I put some 89-octane in the tank, and didn't notice the rattle during ~150mi of driving this weekend. I might not have replicated the exact load conditions where I noticed the rattle originally, but I've still got more than a half left, so I will continue to monitor it.
 
You must log in or register to reply here.

Similar threads

T
Diagnose rattle under shift knob?
2
Replies
32
Views
5K
Anak
Anak
T
XJ shackle with custom springs question.
Replies
11
Views
206
XJlimitedx99
X
B
Jeep xj surging
Replies
11
Views
433
Bmfinney
B
A
Growling under load in 4th, AX15
Replies
3
Views
2K
RCP Phx
R
T
Oil In AIr Filter/Not Passing CA Smog
2
Replies
22
Views
4K
cruiser54
C
Back
Top