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My 710M pulls to the right quite vigurously under braking when I am in 4wd, but keeps a straight line under braking in 2wd. Any ideas?

Keep it in two wheel drive? . Sorry. I could not resist, I also have no idea why,but with the great help on here. You will get an answer soon

When you say "in 4wd", what are you referring to? Having the 1st (leftmost) hydraulic locker engaged? Or something different?

Weird complaint...

Yes, 4wd means that you engage the left (green) locker. The Pinz then pulls to the right when braking. This, however does not happen when I am in 2wd (green locker disengaged).

This is unusual; without any levers pulled, each wheel brakes as it can (brake adjustment, dust, brake fluid contaminaiton, etc.). Pulling the green 4x4 lever links the front axle and rear axles together, so it is not easy to "lock up" the rear wheels under heavy braking, but the left and right wheels are still independent due to the differentials.

To further refine your problem, try this on a safe section of straight road: if it pulls decidedly with the green 4x4 lever pulled down, repeat the test with the center (rear diff lock) pulled also Does braking still pull the same way and amount? Then try releasing the center lever and repeat with the right most lever (front diff lock). Does the braking change? Which ever diff lever is down that stops the pulling, that is the axle that is having a brake problem. This is because locking the diff forces both left and right wheels to turn at the same speed, so if one side is doing more braking force than the other side the diff lock forces the left and right sides to brake the same. Releasing the diff lock will allow the one side that brakes the hardest to make the truck pull to that side.

A leaking brake wheel cylinder will allow the brake fluid to combine with dust to make the brake grab with much more force than normal; you would expect that oils will make the brake work less well, but that is not the case.

However, if your truck only pulls when the green 4x4 lever is pulled then I am stymied; this just doesn't make sense.

Best of luck,

Jim M.
712W and 710M

Thanks Jim, yes it only pulls when the green locker is engaged - weird :?: I will run your suggested tests, clean, adjust and replace wear and tear – and report back next week.

New thought: are all your tires the same type, size, and approximate wear? If one is larger or smaller, engaging 4x4 would probably make braking worse. This is the only thing I have thought of that might match your symptoms.

Happy Holidays,

Jim M.

The Pinz has brand new BF Goodrich 235/85R16’s… I have done Jim’s suggested diff lock test – with the rear diff-lock engaged the Pinz continued to pull, but when I engaged the front diff-lock (rear disengaged or engaged) the Pinz keep straight as an arrow – so I assumed the problem to be with the front diff. I have cleaned, inspected, adjusted and bled the brakes – no visual problems (i.e. pads is only 50% worn, no intrusions or brake fluid - nothing. Upon testing with the centre diff engaged, the Pinz AGAIN pulled to the right (although to a lesser extent). Could it be that there is air trapped in left front brake line (although no bubbles came out when I have bled the lines (I followed a right front, left front, right rear and left rear sequence). Any suggestions? :?:

The Pinz has brand new BF Goodrich 235/85R16’s…

Ahh, new tires. That must be the problem -- Tell you what, if you bring your new tires over to me I'm willing to trade you my worn out BFGs that brake straight...

The only other thing I can think of would be mismatched shoes (old style asbestos on one side, newer non-asbsestos on the other side) or aging brake hoses that swell with pressure. However I'm not certain how the Pinz hydraulic system is designed: is it a dual diagonal system or front to back? Hopefully someone else out there knows; a diagonal system problem could be giving problems.

Anyway, bring those lousy new tires over and I'll be glad to help.

Best of luck,

Jim M.
712W and 710M

If locking your front diff cures the pull, it seems to indicate the problem to be in the front axle, as you observed.

I assume you are aware that the front two brakes adjust backwards of each other. IIRC, the Right Front is backwards from all the other wheels. Also, I assume that you've adjusted both adjusters in each wheel. (Sorry, I don't want to offend you, as I realize this is probably way basic stuff.)

To my knowledge, the furthest out wheel should be bled first, ending with the closest. So the order to bleed them should be Right Rear, Left Rear, Right Front, Left Front. If you've left air somewhere, that would explain the pull.

And lastly, did you try moving the tires around on the truck? Like move the fronts to the rear? It seems pretty unlikely that a funky tire would only show problems during braking, but it might be worth a try.

Another question, is this a problem on a truck you just acquired? Or is it a problem which just started to occur. Did the occurance of the problem coincide with the purchase of the new tires?

I bought the truck a month ago and identified the problem upon testing on our farm. I do not think tyres have anything to do with it and yes I adjusted both front calipers... By the way the manual stated very clearly one should start with the front right then front left then rear right and lastly the rear left. It also seemed odd to me, but hey if the manual says so it will not be without good reason?

Possibly a frozen front left break cylinder, or partially frozen. Lift front left wheel off ground, have one person stand on breaks and try to turn wheel by hand. also remove front left wheel reinstall atleast 3 lug nuts to secure drum, than rotate drum to various angles look thru adjustment hole, have second step on breaks and insure shoes are moving. May be easier to see movement if break adjusters are backed off slightly prior to viewing.

Ed

Hi Ed, nope, can't be the brake cylinder - it pulls only when the centre diff is locked...