83 c2500 auto hard shift P to D

[David Edgerton]

Truck has a hard shift from park to drive. Not the u joints or rear end. Where to investigate next?

 

[Matt69olds]

Idle speed? Engine/transmission mounts?

Is this a new problem? New to you truck? Recent transmission work? Does it bang going into drive, or reverse, or both? If it’s a hard engagement into every gear, check the TV cable adjustment (assuming it’s a 700) or the vacuum modulator line. If the cable is too tight, or the vacuum supply is weak to the modulator, that can raise line pressure higher than it should be.

If this is a new problem, chances are it’s TV cable or vacuum problems. If the trans has been overhauled, or you bought the truck with this problem, your options are to either live with it or be prepared for some “exploratory” surgery.

Do you have access to a pressure gauge that will read to 300psi? The line pressure tap is right above the linkage on the drivers side of the case. It’s 1/8 pipe thread. Connect the gauge, warm the engine, set the idle to 1000 rpm and record the pressure in each gear. If it’s much more than 90-100 in park (depends a lot on the specific model) then line pressure is most likely your problem

 

[David Edgerton]

Had the box off and looked again at the driveshaft. From park to reverse it rotated almost 1 revolution before engaging the wheels to move. In my opinion the rear end. From park to drive not so much and not a hard bang, but drive to reverse, BANG.

 

[Matt69olds]

With that much backlash, no wonder it bangs into gear.

Time to pull the diff cover and stare in awe at the carnage. With that much slop in the rear ended, it should be fairly easy to se what’s wrong.