1993 Other Toyota Models 4 wheel drive problem

POLARBEAR06

MEMBER
1993 TOYOTA
6 CYL
4WD
MANUAL
165,000 MILES

My truck is 1993 T100. It used to be easy to shift in and out of 4 wheel drive and the truck ran fine in 4 wheel up at normal speeds. Now it is very difficult to get out of 4 wheel drive, usually requiring me to stop and back up. It also causes a lot of vibration and the truck to handle terribly at any speed over 5-10 mph. I have already replaced both CV Axles and put a rebuilt front differential in without any change. Can you tell me where to go from here? It may be unrelated but in case it isn't. At about the same time as my 4-wheel drive problem began, my truck's gas mileage went from around 20 mpg to about 12-14 mpg. New plugs, plug wires, coil, distributor, fuel filter, oxygen sensor, and air filter have done nothing. Again. Any suggestions? Beside get a new truck that is. Thanks for the help.

2 Replies

MHPAUTOS

MECHANIC
31,938 POSTS

Hi there, first thing is to check the transfer oil level, are you driving on sealed surfaces in 4X4? What are the tyres like? Are the front worn more than the rear? With manual 4X4's there is no centre differential, (as constant 4X4 have) if driven on firm surfaces for to long, you get what is called transmission creep or bind up, the different dimensions of the wheels albeit minor, will cause the transfer to bind up, this is normally not a problem on dirt or loose surfaces as there is enough slip to keep drive line from binding, when you go into reverse the load is released and the selection can be made easier. If this is the case don't drive on hard surfaces in 4X4 they went really designed for it.

Mark(mhpautos)

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Tuesday, January 1st, 2008 AT 6:37 AM

POLARBEAR06

MEMBER
2 POSTS

OK. Thanks for the help. Here's an update. I have access to some pretty great tools (I'm an aircraft mechanic) and I borescoped my transfer case with this cool fiberoptic system we had. It was pretty ugly. I put in a rebuilt transfer case and things have gotten a little better. The truck handles ok up to about 25 mph now (that's as fast as I tried) but there is still some vibration especially when decellerating. I also still have to stop to get it out of 4 wheel drive. So.I'm left with 3 possibilities. The U-joints on the front driveshaft appear to be fine but the vibration feels similar to what I've felt when a U-joint went bad before. The getting out of 4 wheel drive problem could have something to do with the vacuum assist. Can someone tell me what provides the vacuum for this so I can see where to look? I haven't found any leaks in the lines. And then there's the tires. The front tires have just a bit more wear on them than the back tires. I need new ones anyway so we'll see what that does. If anyone has any other ideas I'l gladly listen. Thanks.

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Sunday, January 20th, 2008 AT 7:50 AM