Hello,

I just bought a GMC Jimmy 1979 in Saudi Arabia. Its equipped with 350 Cui Engine and a Automatic 4X4 Transmission.

Please help me understand as how the 4X4 transmission works as I can see 5 options as Lo LOC, Lo, N, Hi HI LOC. As this is my first experience with a 4X4 trans. What option should I use for a day to day driving with in the metro?

Second, is this truck an All time 4WD car? means the both front and rear differential work together all the time or there is a way engage and disengage the the front differential.

Third, When I shift the gears from Reverse to Drive or Drive to Reverse, a strange sounds comes from the front Axle Drive shaft as it sounds like its lose from the front differential part.

The Truck runs perfect, But I'm just scared with the front Differential noise as in running she makes no strange noises only in Shifting the gears.

Please tell me as what should I do, I replaced the Oil of the front Differential and unfortunately the Oil was very bad and it had some sand or solid tiny granules.

The problem is this there are no ppl hear who understands these kind of machines well.

Hope to hear from you ppl soon.

Regards,

 

Your truck has the NP203 full-time 4wd transfer case. HI is used for normal everyday driving. THIS POST should explain what's going on.

I can tell that your truck is not part-time converted as it still has the stock dust caps over the center of the hubs on the front axle. If you want to figure out how to do a part time conversion, just run a google search for "NP203 part time conversion" and you should find more than enough information.

As far as the noise when changing from forward to reverse or vice verse is likely from slop in the drivetrain. Worn u-joints or larger than typical clearances between the ring & pinion gears in the differentials.

 

Thanks buddy for the response, Yesterday I figured it out with the help of a mechanic that the front differential is connected to the wheel and in between them there is an axle cross (the locals call it front-axle-slip) but its a cross shaped joint and its making noise when shifting the gears as I think its been wearied out so I'll changing that out soon and hope that the noise goes away.

But any ways once again thanks a lot. I think I'll be needing some help as installing the np203 part time converting kit. Could suggest me any good part time conversion kit.

Regards,

 

Hello again,
My Jimmy gets very hot in the summer as now weather is cool but after few month it'll become very hot as Saudi Arabia is a very hot place to live, I have noticed as my Jimmy's motor starts getting hot she starts knocking(noise from the valves) and I can sense the Power lose and plus on long rides she becomes very hot with no power. For this I changed the Radiator and Fan Clutch and I saw a little improvement but not much. Could you please suggest me as how can I keep my motor cold as in cold state her power is at the peak or do I need to change my water pump.

Regards,