Truck pulls laterally under acceleration and braking

[lelandEOD]

So far, I've been unable to identify the cause for this behavior. It's unsettling to say the least. I had sort of learned to live with it until I recently found out [the hard way] that the lateral shift is proportionate to the amount of force input (meaning I can feel a stronger sideways tug the harder I hit the gas pedal). Acceleration isn't the big deal; braking is. I had to panic stop recently from about 70mph and the truck almost changed lanes on me.

Do the symptoms I'm describing sound familiar to anyone?

 

[roadstr6]

Do you have a rear locker? If so, is it a mechanincal locker (not an air or E-locker)? I have a Detroit locker and I have the same issue upon accelerating and decelerating. Braking is most likely a separate issue. If you don't have a locker and you are 100 percent sure of this, check your motor and trans mounts as well as your suspension mounting points (spring and shackle hangers). Also check for a broken leaf in the spring pack.

 

[unklwedy]

Once in a blue moon FJ40's develope some steering slop. There's over 400 pivot points.

 

[PabloCruise]

Drums on rear, or front & rear?

If yes, are they adjusted?

 

[sggoat]

This is a symptom my wife's 95 Camry has--if you accelerate, the car pulls to the right, if you let off the gas, the car drifts left---never seen anything like it--I've heard it described as "torque steer". I have no clue as to how this might relate to a 40

 

[yotafj]

Check you shocks, mine did that when I had my v8 installed in 72 when I hit the gas it pulled right. Put new shocks on and it went away for me. Hard to compare a front wheel drive car to a rear wheel drive one diffrent tq loads one pulls one pushes. Food for thought

 

[Wasim Mehdi]

Look for loose wheel bolts.

 

[chappohj47]

Torque steer does it or suspension centre pins loose my work ute does it

 

[roadstr6]

This is a symptom my wife's 95 Camry has--if you accelerate, the car pulls to the right, if you let off the gas, the car drifts left---never seen anything like it--I've heard it described as "torque steer". I have no clue as to how this might relate to a 40

Torque steer is caused by the transmission transferring torque through axle shafts of different lengths. The Camry transmission is most likely not in the exact center of the car and the driver and passenger CV axles are likely different lengths. Most front wheel drive cars are this way. Ever notice the diff is not centered on the rear axle of the 40? Same thing. Passenger side axle shaft is shorter than the drivers side. This sets up a perfect torque steer situation. Add a lift and a mechanical locker and the situation is more pronounced.

 

[Weber Sarge]

If it consistently goes the same direction it may be a problem with the differential or a broken axle . A locker can do strange things but they usually change direction between acceleration and deceleration .
Sarge

 

[Living in the Past]

Ever notice the diff is not centered on the rear axle of the 40 (all except the last couple of years)?

The 98 100 series was the first time a rear centered diff Land Cruiser was imported to the US. Never seen a rear centered diff on any 4X series.

Before someone corrects me the early FJ40 until sometime in 63 had a centered diff. These was a carry over from the FJ25 that had a centered output from the transfer case. The output on the FJ40 was off set but diff centered for the first few years.

 

[roadstr6]

If it consistently goes the same direction it may be a problem with the differential or a broken axle . A locker can do strange things but they usually change direction between acceleration and deceleration .
Sarge

That's what mine does. Steers into the ditch when I jab the gas and steers into oncoming traffic when I slow down for sharp curves. Fun stuff!

 

[Diesel Cruiserman]

I had this problem once, loose ubolts

 

[Weber Sarge]

Broken spring center pins can do some interesting things too - look for metal marks around the u-bolts and spring plates .
Sarge

 

[lelandEOD]

You gentlemen are awesome. I had a buddy shove the truck sideways while I looked under the rear end. Sure enough, my right side axle U-bolts were loose enough to allow the axle to move around. YIKES!

Now, here's the next issue: This problem was likely created by the use of 4° caster shims that prevented the leaf spring centering pin from contacting the axle perch sufficiently. I have looked all over: Summit Racing, Man-a-fre, Marlin Crawler, 4Wheelparts, etc. and I can't find flippin' alignment pins with extended heads anywhere! I can't be the first person to have this issue... what gives? This is one of the only references I have been able to find: http://www.jalopyjournal.com/forum/...-i-found-on-the-net-i-cut-them-to-fit.452460/


Also, what size (length and diameter) are the factory center pins?

 

[lelandEOD]

New question:

Am I supposed to find center pins that have a longer head length to protrude through the caster shim or am I just supposed to buy center pins with a longer threaded length and bolt the caster shim to the spring pack?

 

[lcwizard]

Depending on whether your center pins are stock ( 8mm-5/16 ) or 3/8 you may need what spring shops call center pin spacers.
It's just a fancy name for a short piece of thin wall tubing with the same ID as the bolt diameter. they are usually about 3/8~1/2"
long. It stands the head up that distance
There is a Chrysler center pin in 5/16 diameter that has about a 5/8" tall head. When I used to build shackle reversals I would order
those by the hundred from Security Steel. Don't remember the part number. I just referred to them as the 5/16 Chrysler center pin with the tall head. They always new what I was talking about. I guess that's reasonable since their only business is suspension hardware

 

[lcwizard]

something like this...you can make your own if need be

 

[lcwizard]

chrysler tall head style and another set of pins commercial spacers

 

[lelandEOD]

Damn... so simple it didn't even dawn on me. Thanks! If someone can tell me the FJ40 center pin diameter, I'll get a set ordered right now!