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Old 11-18-2012, 06:20 AM
90K1500 90K1500 is offline
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700R4 troubles

Hello everyone!

I will keep this short. I have a 1990 K1500 4x4. The 700R4 lost 3rd-4th randomly one day. I pulled the transmission and ordered an ATSG manual along with a rebuild kit from TransTec.

My conclusion was the the 3-4 clutches were toast along with the input drum piston seal (common problem I hear). I made use of all the information floating about the internet.

Now here is the problem:
After the rebuild I installed the transmission and got a similar problem that I started with.

Rev: Very Strong
1st: Very Strong
2nd: Very Strong
3rd: Won't Shift Into
4th: Won't Shift Into

I have adjusted the TV cable with no luck. When I place the gear selector into "OD" I get no response from the transmission (like it's still in Neutral). When I shift to "D" it will engage.

During the test drive it will shift from 1-2 no problem but when it comes time for 3rd gear to engage the transmission does nothing but hold 2nd gear. If i let off the throttle it will engine brake (like it was in "2" at high RPM's).

I am looking for any and every possible problem. So far my list of things to check are:

Servo - bad 3/4 seals (although all new), possibly assembled wrong?
Pump - has something in it for the 3-4 shift
3-4 Accumulator - This seemed fine during reassembly
Input Drum & Pump Seals - I ended up using the scarf cut seals.
Input Drum - I did air test the piston, seemed fine. I did have some confusion with all the steels since all the plates feel out of order during disassembly. Clearances measured out in the end.
Sprag/Low & Reverse Roller - Pretty sure that I got these installed correctly (the Low & Reverse Roller for sure).
Valve Body: Didn't check every item on it. I am sure the check balls are installed in the right locations.

Any and all help is appreciated by this veteran! Cheers!

Last edited by 90K1500; 11-18-2012 at 06:26 AM.
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