Throttle steers the truck

[Chuck Tribolet]

When I'm cruising down the freeway, get on the gas, the nose of the truck will twitch left and then back to a straight line.
If I lift quickly, it will twitch right, then back on a straight line. What''s up?

Some thoughts:
Motor mounts
Shocks
suspension bushings.

[Pathy415]

It doesn't look like you live in a salt belt so I'm with you on the possible worn suspension components. I'd check for possible stress cracks in addition to the mentioned items. The chassis sounds like it's flexing somewhere.

[fueler]

first thing id check all the 5-link rear suspension bushings (all you have is lower trailing arms, upper trailing arms, and panhard rod).... with the truck parked and e-brake yanked, get underneath and have a buddy rock the truck back and forth in several different directions and see if you can visually pinpoint any bushings that have excessive play....

[Chuck Tribolet]

I don't live in the salt belt, but my truck has launched my boat in the ocean about 70 days a year for almost ten years. But
my boat trailer has a really long tongue and the boat sits low, so I usually don't even get the tires wet.

Rear suspension bushings was what I was thinking. I'm open to other ideas.

[ARKQX33V6]

Chuck off the top of my head and since you are asking for ideas...
Throttle on then off suddenly torques the drive shaft one way while the motor itself is twisted the other way. Verify the motor mounts.

The rear end diff if a limited slip, with extreme torque applied by the drive shaft it may cause the wheels at the rear to lock one side then the other as torque changes even though your on non slip road way.

Front suspension and drive train, tire pressures.

Does your 4 wheel drive engage by a motor, could that motor have been energized and try to engage the front? Wild guess but who knows.

Just a bad section of road, similar experience on Ontario roads, heavy trucks putting grooves into the highway and your truck simply follows, like snakes repairs ( tar surfaces filling cracks) with a motorcycle. The tires track along these tracks. Your tires are real new? Too good traction or they are bald and can't track like they should.

I hope this helps out.

[Chuck Tribolet]

It is a limited slip. I wouldn't call it extreme torque, just lifting off and gassing it on the freeway in fifth gear at about 2800
RPM. It even does it engaging and disengaging the cruise control.

4x4 is engaged with a lever, so it's not that.

Tire pressures are OK, just checked them the other day.

Tires are not new. Will get replaced before the fall rains. BTW, bald tires have BETTER traction than new. The voice of
experience from my autocross days in my 240-Z.

I checked the rear bushings yesterday. I've got one upper trailing link bushing that's tired, but they were far worse that
that before and it didn't do this.

Motor mounts are the next to check when I have the pan off to change the oil next week.

[ARKQX33V6]

Very interesting! Yea I know about bald tire traction, bald or ribbed or lugs they all have their quirks. Even at engaging cruise, TORQUE CONVERTER anomalies, vanes distorted, even transmission problems with clutch band wear.

Are you in w WD or 2 WD or playing the middle in Auto?

[Chuck Tribolet]

2WD. It's a 4x4, but there's no automatic mode on an '01 PF. Just 2WD, 4WD High Range, and 4WD Low Range, all manually selected. This happens in 2WD mode.

[Chris.m]

but there's no automatic mode on an '01 PF.

My Pathfinder (manufactured in May of '00) has the automatic mode. I guess I'm lucky then,

[Chuck Tribolet]

Maybe that's an automatic transmission or LE option. I've got a stick shift SE, and it doesn't have an automatic 4WD, which
is fine with me. I only use 4WD on boat launch ramps and a little dirt roading to do maintenance on my bluebird house trail.

[Chuck Tribolet]

I did the 195,000 mile oil change tonight. I can really only see one motor mount (passenger's side), and I don't see any place
I'd want to jack that thin aluminum upper oil pan to see what moves. The FSM does not contain the phrase "motor mount".
Any thoughts?

I've left the pan off to make it easier to check anything that somebody comes up with.


Chuck

[ARKQX33V6]

Chuck with the pan off a bearing surface 4 x 4 lumber at the edges can be used to apply upward force and eyeball the mounts, but then again the mounts being loose may not affect the steering problems you experience.

In scanning the Service book to jog my memory and to help here are some thoughts:
Movement of steering gear when stopped on dry pavement to see if gear box is loose in its mounting.

Steering rack centered in movement on the flat does car go straight, when hands off the wheel.

Steering transfer gear, presets are critical and there may be wear in there causing the movement.

Tie rods and steering linkages becoming worn or over tight.

Brakes, front wheel drag, from side to side, there is a preload on the bearing, maybe a worn bearing playing with this preload with the brakes.

Just a few thoughts!

[Chuck Tribolet]

When I changed the oil on Monday, I also rotated the tires front to rear, and it's doing it quite a bit less.

Truck goes straight with hands off.

I'll still check the rest of the stuff that's suggested.

[ARKQX33V6]

Anything being resolved? Check those ex front tires for separations.

[Chuck Tribolet]

Nothing yet.

No obvious separations on the ex-front tires.

[UITexan]

Your rear trailing arm bushings are bad. Don't worry too much about the upper control arms. Replacing the lower ones will fix your problem. You have a couple of options:

Replace the entire control arm with bushing already installed (easiest, most expensive)
Replace only the bushings (requires a press if you use standard bushings)
Replace the bushings with poly bushings (expensive parts, but no press required)

I did the last one. You can buy the poly bushings from Automotive Customizers (http://www.4x4parts.com). I recommend the split design. Otherwise, you will need a press.

If you need a how to, let me know. There should be one somewhere on this site. Just do a search.

[Chuck Tribolet]

The problem came back this weekend.

I'll check them again, but the lower control arms seemed OK. One upper control arm bushing had a little wiggle in it.
I've done the uppers already twice (196K miles on the truck).

I'll have to wait for it to quit raining (It never rains in Northern California in June).


Chuck

[UITexan]

I have 228k on my '02 Pathy. Do the poly bushings on both the lowers and uppers and you will never have to replace the bushings again.

Trust me, the lower control arm bushings are the problem. If you are at 196k and have not replaced the lower control arm bushings, consider yourself lucky. I can almost guarantee you that the lower control arm bushings are the problem. You won't be able to wiggle it by hand because everything back there is so heavy, namely the differential, which is also held by the panhard rod. Mine was so bad, the car would shake uncontrollably when the throttle was released. When I took out the bushings, they "looked" fine, but were obviously worn. I replaced them with poly bushings and the car is ready for the next 100k miles!

Note: poly bushings are a bit harder to install due to the minimal flex and will also make your ride a little stiffer

[Chuck Tribolet]

I had another look at the lower bushings yesterday and they are a bit suspect, so I'll probably do those soon. I'm leaning towards the two piece bushings.