Hi All,

I finally got the rusted out rear trailing arms replaced and my 99 Expy back on the road but now have another problem

When I put the dash selector in 4 Low the transfer case switches and it definitely goes into low range based on the speed.

But if I turn the wheels while it is in 4 Low there is a REALLY loud banging sound that seems to be coming from the center of the vehicle where the transfer case is. I mean it sounds like somebody is whacking the frame with a sledge hammer.

I was going pretty slow - like the speed you would pull into a parking space - and it seemed to be regular but random - happening about once per second.

I shifted out of 4 Low and the banging noise goes away and I have Googled the crap out of this symptom and best I can tell my transfer case may be toast.

Anybody else had this happen?

More importantly, anybody know how these transfer cases work to be able to tell me if this is something that will fail in a way that will leave me stranded if I pull fuse 104 to keep it from trying to engage anything?

I looked up what I could find online and it appears that with fuse 104 pulled the transfer case should drive straight through to the rear wheels like a 4x2 would which would be good enough to get me until the weather is warmer. But if there is some other failure mode I am not aware of I would like to know before I get stranded

Thanks in advance for any tips on these transfer cases.

RP

 

Were you on dry pavement?

 

You don't engage 4lo on dry surfaces turning the wheels. If it isn't dirt, grass, or gravel don't do it. Especially turning you'll risk breaking something in the driveline. Even a slight turn in 4lo on pavement will jerk and buck. Does it make the noise while going straight?

 

So I did this in a gravel driveway and after finding a parts diagram it looks like the transfer case has no center differential so the loud knocking makes sense.

It does not make the loud knocking sound when going straight but the reason I was even doing all of this was it was making a different and much less loud thump when accelerating going forward straight. I have had time to research that as well and when it warms up today I am going to test to see if pulling fuse 104 stops that

Thanks for the advice on 4lo - the freaking manual says nothing about that but oh well live and learn.

 

It isn’t just 4Lo, you shouldn’t engage 4Hi on dry surfaces either. The manual does say it, but not in a big flashy way. See the bottom of page 114.