Hi

I have problem with my 4WD turning on. I can turn it on but after driving less than 100m it switch of with noisy bang. And I do not know if I should buy new differential or try to repair old one. Any idea what could be damaged?

Cheers, Marcin

 

Most likely a fautly vacuum switch on the transfer case. Either that or a faulty vacuum actuator for the engagement of the front axle... Run as search on common 4wd or 4x4 problems.

*Moving to Steering, Suspension, & Drivetrain*

 

Any idea how to check it instead of buying diff first? And maybe important is that 4WD is turned on but for short time only.

MK

 

Are you absolutely sure that the 4wd has actually engaged and then is slipping out? Or is it more likely that it is taking quite awhile for the front axle to engage.

I highly doubt you need a new front diff. Most common problem areas in 4wd engagement are the vacuum switch on the transfer case (~$30 or so IIRC), or the vacuum actuator either leaking or the cable freezing up that runs to the front diff.

 

I am absolutely sure that 4WD has actually engaged and then is slipping out. I done some tests on sandy surface. After driving some meteres (50-100m) 4WD was disconected with strong bang. After turning of 4WD and turning again on the same has happened. I can repeat it any time I want.

Marcin

 

And one more information. I had some problems with switching on 4WD - it was looking as to low air pressure to turn 4WD on, but after some tests switch on/of many times it started to switch on every time.

Marcin

 

Sorry for so many post but I am still thinking about my car problem. And I have one (maybe stupid question) - how 4WD is being kept turning on? Is it only air pressure or any mechanical lock? If only air pressure it seems to be air problem (actuator or so on) if mechanical lock maybe the lock is broken?

Marcin

 

OK. I have discussion with my mechanic (it is second Blazer he ever saw, but he knows Jeep Cherokee). Whe I left my car at mornig he notices that this rubber ball (what was it - actuator?) tried to pull cord to turn 4WD on but not enough. He decided to move little this rubber ball and the it started to turn 4WD on but after short drive 4 WD turned off with strange noise/bang. And now I do not know if:
1) any air pipe, actuator or switch is bad and is not enough air pressure to turn 4WD on and keep it on?
2) any part of front diff is broken and 4WD can't be kept on

Any idea? Any advice? How to check? This rubber ball all the time tries to move cord to switch 4WD on but I do not know how to check if movement or strenght are proper. Please help!

Marcin

 

Check the vacuum hoses that are on top of the brake booster. They're about 3/16" in diameter. Often times those split or rot out and won't hold enough vacuum to keep it in 4wd.