tranny has reverse but no forward

[m.lander]

i have a 1972 c10 with a 350 motor and a 350 tranny. my problem is when i shift into reverse with the shifter on the column it goes into gear but when i shift into l1, l2 or d the truck wont move. if i try to shift the tranny with my hand on the linkage attached to the tranny it smoothly goes into reverse park and neutral but "slips past the drive gears. what could this be? thanks for the help

[JimKshortstep4x4]

Welcome to the board from West Michigan!

Sounds like a strange problem. Can you hear a definite click when you shift it either way? I would drop the pan and check out the internal shift linkage as it can come apart.

Jim

[bobthecop]

Welcome from Oklahoma

[BACKYARD88]

from South Texas. I'd drop the pan and inspect the manual valve and linkage. Maybe the teeth on the detent to see if they're worn.

[m.lander]

thanks for the help. sometimes it will grab the d gear but less than half the time. if i put it in low L1 then shift up to D it will usually work but seldom will it work by going from park straight to D. ?

[BACKYARD88]

Might want to check the linkage on the outside of the trans firts if you havent already. When I first got my truck it was worn so bad you had to play with it to get in gear. There's a U shaped piece on the trans and another one on the linkage and there was alot of slack in mine.

[mnunn454]

So I think you're saying sometimes it goes into drive and sometimes it doesn't.

Sounds like a shifter linkage problem to me, rather than an internal tranny problem.

Are all the linkages tight?

With the engine off, wheels chocked, put the shifter in low. Then under the hood, at the top end, disconnect the shift linkage at the point where it fits in the shift arm that extends out of the steering column. Then get under the vehicle and see if the shift rod linkage that you just disconnected can be moved any further down and back. (i.e. will the shift rod move further down and back toward the rear, causing in turn the the tranny bellcrank to rotate counterclockwise).

If it will rotate more and you can hear a noticeable click as you move it, , then your linkage isn't allowing the arm (bellcrank) on the tranny to reach the drive, 2nd or low positions and you'll need to adjust or replace your linkage parts.

If the tranny bellcrank is already going all the way into low then very likely you've got an internal problem with the trans.


Hope it helps. Good luck.

[m.lander]

If I disconnect the linkage on the outside of the tranny and try to turn the"u shaped peice" attached to the tranny by hand it still wont shift correctly so I know its not the linkage. Im thinking its the internal linkage as someone stated above. Im draining the pan right now so hopefully I will know soon. Any mor ideas are welcome and thanks again to everyone who is helping with this.

[m.lander]

what is the manual valve backyard88 is talking about? is the internal parts that need to be checked visible with only droping the pan?

[JimKshortstep4x4]

The manual valve is what shifts the transmission and is moved by the internal linkage. It is a spool valve which routes the fluid depending on its position. The internal linkage is moved by the external linkage since there is a connecting shaft that goes into the transmission.

When you get the pan off look up at the shifter side and you should be able to see the linkage. Move the external linkage and check to make sure the internal linkage moves the manual valve. If there is a problem it is usually readily apparent.

Here is the only picture of the internal shifting linkage that I could come up with.

Good luck!

Jim

[m.lander]

I hate to admit this but I, sometime back, put a fairly heavy magnet in the pan to catch debris. this magnet was ignorantly put in the pan. Guess where? Yes friends right under the internal linkage restricting its movement to some degree. Thanks everyone for all the help.

Mark