Is my 4HI engaging?

KeithsHD · May 14, 2004

I just got a new (old) truck. It's a 93 Chevy 2500 reg cab long bed 6.5L turbo diesel. I downsized (pricewise at least!) from an 01 2500HD.

I'm concerned that my 4WD isn't engaging. I put it in 4 HI on gravel and can still spin the rear tires. And when I turn a tight circle it doesn't push like my 01 did. It just doesn't feel like it's in 4WD at all.

Years ago I had a 90 Blazer and I seem to recall that it was quite noticable when it was in 4HI.

My 93 does not seem to have a locking diff (G80 is not listed in the RPO codes).

I believe the truck has 4.10s (according to the RPO codes again).

Am I stupid? (I feel stupid!)

Thanks.

Keith

Shaners · May 14, 2004

It's very possible that the thermal actuators are bad on the front axle and therefore it isn't engaging. This is a fairly common problem on trucks from the 90's and late 80's

496 CUBIC INCHES · May 14, 2004

I think Shaners may have it right. My brothers 92 Z-71 had the same problem 2-3 times,it ended up costing him about $75 to fix IIRC.

496 CUBIC INCHES · May 14, 2004

If I'm in 4-HI on a flat gravel road my 01 HD with the BB won't spin the tires either. Between the torque nannie and the weight of the truck it just takes off like a rocket.

KeithsHD · May 14, 2004

I think Shaners may have it right. My brothers 92 Z-71 had the same problem 2-3 times,it ended up costing him about $75 to fix IIRC.

Any more details on what needs to be checked or replaced here? I'm fairly capable, just darn near clueless.

Thanks a lot!

Keith

citydriver · May 15, 2004

Try puttin the truck up on jack stands,turn the IGN. ON but DONT START IT....put the transfer case in 4HI then spin the front wheels by hand...this should tell you if the front axle is engaging at least...the front driveshaft should turn (tranny in NEUTRAL).....the rear tires most likely wont spin out at all when the trk is in 4WD...

but the fronts might if you have the wheels turned,however that diesel is kinda heavy,so it might take quite a bit to break traction....try some MUD

KeithsHD · May 15, 2004

I'll put it up on jack stands when I get a chance and see what happens.

Thanks

Keith

99-2door · May 15, 2004

If the light that shows the front wheels are engaged on the shifter plate comes on then the front is engaging. That light only comes on when the front diff is engaged.

Shaners · May 17, 2004

If the light that shows the front wheels are engaged on the shifter plate comes on then the front is engaging. That light only comes on when the front diff is engaged.

That is correct about the light (as long as it isn't burnt out).

My '88 S-10 had this problem with about 10K on the odometer. The truck would take longer and longer to engage in 4wd.

When I finally took it into the shop, it would take about 1/2 mile to get it to light the indicator and engage the front end. (That doesn't do you much good if you stuff your truck in a snow drift in 2wd)

KeithsHD · May 17, 2004

If the light that shows the front wheels are engaged on the shifter plate comes on then the front is engaging. That light only comes on when the front diff is engaged.

The light does not appear to come on in the indicator diagram.