My transmision is slipping i can feel it try to engage in reverse but it won,t pull it up a slight hill , after it gets heated up it won,t start out in low gear , but after you get to 35 miles an hour it wil shift smoothly , it started this 2 days ago .

Make sure the 4wd shifter is in correct position and hasn't slipped out of correct spot to get you moving forward.

This sounds like your trans is slipping. If you wait, it can get very expensive.

Look at the transmission fluid on a level surface as the vehicle is running . Is the level correct? Now how about the color is it? Is it blackish ? Low level transmission fluid will not allow the vehicle to go in gears correctly. It will engage hard. Now the color dark is the clutch fiber the transmission is out of adjustment and will operate out of range. Now if it slip out going up a hill there is a great demand on the transmission . The band which is a clutch fiber must hold the drum in order to transfer power if it can't the transmission slips and a overhaul will be in order. Just dont overlook the probability,and the simple solution and yes you will definetly need to rebuild the transmission

it may be a bad transmission modulator valve located on the side of your transmission,vacum operated. a sudden downshift or forward shift when unexpected is sign of a bad modulator valve or a vacum leak to the transmission.best to shop around for a garage w/references when it comes to transmission work though. check all the vacum lines to your transmision,you need to look on the underneath side of your truck on the side of transmission for a loose or disconnected vacum line on the side of the transmission. when you feel the vacum line,follow it to the top of engine,the vacum line is about 3/8th line,and may be disconnected or losing air. to make this short,when you drive the car,start out in low gear and shift the transmission,manually from 1st to 2nd to 3rd does it do right with no slipping? if it does this right and shifts great manually,the modulator valve on the side of the transmissions bad,or a bad vacum leak in-between.thank you for choosing fixya.com

may be low on fluid or it is going bad, a good way to tell is try pulling something and see if it will.

Have you serviced the transmission latley? fluid, filter, band adjustment

Usually under heavy throttle causing the slip is caused by a seal in the pump leaking off hydraulic pressure letting the clutches slip.

Does it slip in all gears or just 1st.?
Does it slip in reverse?
The reason I ask this is because 1st and reverse use different fluid pathways,

also you can take it to a tranny shop and have them check the fluid pressure at the accumlator port to determine what the exact problem is,but my advice is to just drive it easy and make it last as long as you can,a new or rebuild tranny from a dealer would run 2500 or more.

there is a website www.car-part.com that you can use to find a replacement transmission

If its automatic, you need a new transmission. Manual transmission, keep trying to switch gears and maybe it will slip into reverse. Or you could do what I do, don't pull into anywhere unless it's a slight hill that you can coast in Neutral backwards or have someone push you in Neutral.

Change your gearbox oil, and clean out the oil strainer.
Should help.

( On some models, you have to remove the gearbox oil pan to clean the strainer )

Well, the best way is to place the vehicle on a hoist and raise all 4 wheels off the ground and put it in 4WD and see if all the wheels start turning.

Another way is to make a really sharp (slow) turn while the unit is in 4 wheel high or 4 wheel low on dry pavement. You should be able to feel the driveline wrap-up caused by the front wheels trying to grab during the hard turn.

4 Low should be easily distinguishable from 4 High as well as 2 Whl when you accelerate and it feels like the transmision is stuck in low gear and the engine starts screaming for mercy at high RPM and you are only doing 30 MPH.

yep, sounds like your transmissions on its last leg, mabye you can get by, by starting in 2nd, if you have the option lol, but auto tran's are pretty cheap on ebay or try www.supraforums.com seen one for 300$