Engine smokes when put in 4WD

[DerekTJeep]

One time when I was driving on highway and put my '89 GW into 4WD. However, the engine smoked. I had to pull over to let the smoke clear. I then drove the rest of way in 2 WD. What would the problem be? Powertrain? transfer case?

Derek

[gsmikie]

bad vac switch on transfer case ???

[davez26]

I'm thinking the vacuum switch has a bad diaphram,so when you swith to four wheel drive and apply vacuum, it sucks the fluid out and burns it in the motor. my .02.

[AJ Johnson]

yeah... on the automatic trannys with vacuum modulators, the same thing will happen if the vac. mod. leaks.. sucks that red stuff in and spews it out as white stuff!
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