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Discussion Starter #1
I have just swapped my PowerGlide for a 700R4, and after a week of work its done. But, it wont shift to 4th. It could be a stuck 3-4 shift valve, (tranny guy) but I dont know if I can fix it by dropping the valve body or not....Any ideas?
Its in a '69 Ragtop, with colum shift. 350-4bbl. Thanks, Mark
 

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If you are like me, the problem is the shifter can't stroke the distance to make all the gears. Crawl under and disconnect the linkage from the bellcrank on the transmission. Then turn the bellcrank to L1(can be done with your hand) and have your assistant put the shifter in L1. MAKE SURE IT WON'T ROLL OVER YOUR ASSISTANT. Chances are the cable doesn't line up with the hole.

The stock shifter strokes 2". In order to span park to L1 in 2", you'll have to shorten the bellcrank. I cut mine and welded it back together again.

It will work fine like this, but there is another step you can take. The detent plate in the shifter could stand to be modified slightly. There are a coulple of places you can grind off and get the correct detent operation out of your shifter.
 

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Discussion Starter #3
I cut the rod between the bellcrank and the shift lever when I put the 700 in. I dont need full stroke, as I just want P,R,N,D,3,2. I leave it in D, which is 4th or OD with a 700. I dont usually manually shift it, as it works fine in Drive. So, I dont think the problem is with the linkage.......its not a real big deal, as I dont drive a lot of freeway trips, but I know it should go into OD......Thanks for your help.
 

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I see your point. I'm going to have to defer to someone else until I can get my manual out and ponder.
 

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Discussion Starter #5
If it is the 3-4 shift valve, can I get to it from the valve body, and maybe just buy a new one or somehow get it unstuck? Just a thought. Any tranny guys out there?
 

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It could be the 3-4 upshift valve. This is in the valve body which would need to be dropped for access.

Sounds like you are sure that the shifter is in OD (4th) so no dwelling on that.

The first thing I would check is the TV cable geometry. This is the cable that attaches to the carb/TB throttle linkage. It controls transmission line pressure and part throttle shift points.

Bob.
 

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Discussion Starter #7
I have the TV cable set per the Bowtie Overdrives instructions. It shifts very nicely b/t first, second & third. But, it just wont upshift to OD. I am reluctant to change the TV cable setting as it seems fine in first thru third. If I pull the VB off, is the 3-4 shift valve a replaceble item? Can I take it out of the VB and inspect it? Thanks, Mark
 

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Yes, the 3-4 valve is removable and replaceable. If you do this you may want to purchase the GM part #8673948. This kit includes a new 3-4 upshift valve/sleeve/spring and a larger boost valve (along with a pan gasket).

It is called the B body fix kit or such. This 3-4 upshift valve will prevent a high speed (> ca. 75 mph) WOT downshift to 3rd. The boost valve will increase line pressure for better holding of the clutches. **Note that this kit ONLY works on '87 & up 700R4/4L60's.**

While in there check the TV valve line up for sticking and/or broken/bent springs.

Bob.
 

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Originally posted by msw13:
How do I find the 3-4 valve in the VB? Is it easy to identify? Mark
Actually it is easy to identify. It is the only sleeve with a half moon on the exposed end. Once you get the kit check the sleeve and you will see what I mean.

Also note how the roll pin retains the sleeve through the slot in the side. It also lines up with the half moon.

RBob.
 

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Discussion Starter #11
RBob,
Thanks for the tip. Have you rebuilt a VB before?
It looks fairly straigtforward. Are there any things I need to know before I do it? Mark
 
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