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My 700R4 won't hold first (low) gear!

11K views 4 replies 3 participants last post by  Bayley 
#1 ·
Many years ago, I had a perfectly fine working 700R4 that performed exactly how I wanted it to. The B&M shift improvement kit gave me nice control over all my shifts at any RPM.

A few years back, I decided to have my trans "freshened up" by a local guy that does trans work out of his barn. Ever since I got the trans back him, I've never been able to "hold" the transmission in first gear. Even with the shifter in "1", the transmission will still shift into 2nd as if it was in "D" (or OD For that matter).

The shift point will change as I give more throttle (e.g. pull on the trottle valve) but still automatically shifts into second. The 1st to 2nd shift is nice and firm... I just wish I could control it manually like I once used to before this last rebuild.

Anybody have any ideas? I am totally stumped. The orignal trans guy is totally stumped (that doesn't say much). The "new" trans guy is also totally stumped (that says even less than the first guy).

The trans is out of 1987.5 Limited edition Z28 with a 350V8. It's right on the transition line of when they swapped everything over. I'm being told I have a late model valve body with an early model case. Maybe it's the other way around, but nobody is sure what I've got. Hopefully this problem is simple to fix.

HELP!!!
 
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#3 ·
Early design 700 tranny will upshift to 2nd gear while the shifter is in 1st.

You can do 1 of 2 things;

Install a larger low/reverse boost valve (.296 diameter)... or install a TransGo shift kit...

700- 2 & 3 kit , will over ride the command to upshift from 1st to 2nd gear while the shifter is in 1st gear.

IF you have a late 1987 & newer 700 tranny, perhaps the shifter adjustment is out or your tranny builder did something I am not thinking of at the moment. Could be mismatched parts
 
#4 ·
Crosley said:
Early design 700 tranny will upshift to 2nd gear while the shifter is in 1st.
Yes, but that is supposed to be at WOT. My situation has it where the transmisison will automatically shift into 2nd gear even if I'm idling down the driveway with the gear selector in 1st. This is not the normal operation of any 700R4 I've ever seen before... early or late model.

I must have checked the cable assembly a zillion times to make sure the shifter is indeed pulling the cable far enough to engage 1st gear.

I t just puzzles me that I NEVER had this problem with this same transmission until I recently had the transmission gone through. Did he forget something when he reinstalled the valve assembly?


Crosley said:
You can do 1 of 2 things;

Install a larger low/reverse boost valve (.296 diameter)... or install a TransGo shift kit...
It might come down to that. I tried installing a TCI manual valve body, but the "fabulous" TCI kit wouldn't engage 2nd or 4th gear (the servo otherwise works just fine). Never mind the fact that it burnt up about $400 in brand spanking new clutchs and bands buring my three mile test drive.

TCI = dog poop


Crosley said:
Could be mismatched parts
I hope you are wrong... but fear that you are right. :(
 
#5 ·
Jmark said:
Are you sure that your "barn builder" trans shop used YOUR old trans and not a different one that he had laying around?
I think both you and Crosley are looing in the right areas. I'm starting to think my barn builder grabbed an early model valve body since it "looks" like a pre-87 trans... even though it is an 87.5 trans. :(

What type of kits come with an etirely new valve body? Like I mentioned in my original post, I tried to use a TCI manual valve body, but that has been an utter failure; 100% TCI's fault.
:pain:
 
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