What transmission is in my 1996 gmc 1500 with a 305 vortec? it is an automatic with overdrive. is it a 4l6e or a 700r?

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yes i imagine so. they are the same block but with different intakes.

SOURCE: transmission wont shift into any forward gears or

4WD! the transfer case is not stuck in neutral is it? Fluid levels are good? Have you noticed a decrease in mileage or power prior to this problem? If no then time to take it in for service it sounds like. Transmission fluid is not consummed, so if it leaked out then you may be able to fill it up and get the leak fixed, if too late then its a rebuild on the tranny.

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It is on the top backside of the engine block, behind the intake manifold mounted into the top of the block. You will have to lean up over the engine to see it.

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SOURCE: 1996 GMC Jimmy will not shift into overdrive.

4th gear failure is a common problem with this transmission, assuming it is an automatic. You should have the vehicle checked for codes by a qualified repair center with the proper scan tool. Also, check fluid level and condition. More often than not, the trans loses 3rd and 4th gear, as these are working off the same set of clutches. 3-4 clutches apply in 3rd, and when the 4th shift is made the 2-4 band applies giving you overdrive. If you have no engine braking in manual 3rd, you definitely have a mechanical failure, no 4th could be an electrical, or mechanical fault.

SOURCE: GMC 1500 Auto, will not shift back into park?

Climb under your pickup and look where the cable connects to the side of the transmission and make sure there is not any mud around the cable or around the shift linkage hookup. If so clean it off and see if it will shift. We have found many of these with mud caked around the shift linkage or a lot of ice buildup and wont allow it to shift into park.