TH400 shift problems (At the column)

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Chaz

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Chaz
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1980
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V1500 Suburban
Engine Size
350 tbi/th400/np241c
Hoping you transmission guys can help out with this. Im having problems shifting my TH400 transmission from Park to Drive. To be clear the transmission operates perfectly when in Drive shifting through the gears normally and it drives fine. The problem im having is with the column shift. When shifting from Park to Drive it will go over Reverse and Neutral but it just jams and stops before engaging Drive. What I do then is back it up into Reverse and the transmission engages Reverse. Then from Reverse I can pull it out of Reverse, move the column shift to the right and it then engages Drive. I disassembled the linkage under the truck and I couldnt see any obvious damage or worn parts. I was able to rotate the shift (Pin?) which the linkage connects to bottom left side of the trans. It seemed to go through all the gears when i rotated it by hand. Not sure if its a linkage problem or if its actually something inside the trans thats going bad.

I normally shift by feel as the transmission indicator on the column (one with the wire) has been broke for a long time. The only other thing I can say is the only other time I have ever had trouble shifting the trans is when I was on a trail somewhere and the truck was articulated and it didnt want to shift due to linkage binding due to the articulation, similar to whats its doing now. So hoping its just linkage and not pins going bad inside the trans.

Any advice from you guys is greatly appreciated. Trying to keep the beast on the road....
 

Chaz

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Bump......
 

Dave M

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Hard to diagnose when you can't see it. Assuming it's mechanical linkage, get under the truck and remove the cross linkage from trans to chassis. Pivot the trans selector through the full range P to L make sure it moves and "clicks" as should. Grab the column shift and now see if that moves freely, feel for the notches in the selector. Now look at the cross bar, is it bent correctly. Put it back in place, (column arm still disconnected) and rotate the cross linkage, check the hook end is not binding in the 'slot' of the trans selector. Also check rear trans mount for movement
 

Chaz

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Chaz
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1980
Truck Model
V1500 Suburban
Engine Size
350 tbi/th400/np241c
Aw thanks for the reply. Turned out to be the steering column. Mechanic rebuilt the steering column for 420 bucks and now everything works great again. I dont know what he actually did inside that steering column but he completely removed the column and sent it to a shop.
 

shanegtr

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R2500 Suburban
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I've been having a similar issue lately with my burb. Very hard to shift from P through to D, cant really feel any of the gear detents. Cant get the trans into 2 or low with the shifter. I need to disconnect the shift mechanism and see where the issue lies - in the trans or shifter
 

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