iroc2121

I have a 700R-4 in an iroc and am experiencing slipping in my "drive" sequence. the tranny slips while shifting between 1-2 and 2-3. the overdrive sequence shifts perfect and the first and second gear sequences shift fine even while shifted manually. i'm thinking its just a stuck or gummed up valve but i'm not exactly sure. i was advised to put J&W Trans-x transmission treatment in it to help re-seal and open up the valves but i've heard some bad things about using a detergent in an older tranny? i would prefer to not fry my tranny but am considering a GM certified tranny swap. Should i go with a rebuilt tranny from a certified mechanic or the GM swap if i end up dropping it? any prior experience or suggestions would be much appreciated!

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Pat Hall

Hey, since your other thread got locked, I figured I'd reply to this one. I've used Lucas brand trans treatment in mine before with good results. You don't have to worry about draining it out and replacing the fluid either. You can leave it in there and it won't hurt anything. However, I would suggest taking off the fluid pan and replacing the filter. It's always a good idea to put a new filter in, plus you'll be replacing a good amount of the fluid with new stuff once you put the pan back on. Just put a bottle of the Lucas stuff in there when you're refilling the trans. I picked up a bottle of it at Checker Auto Parts. It's pretty common to find at most parts stores. Btw, I agree that the one guy was pretty harsh in his reply. If he wants to play moderator, maybe he ought to become one. Otherwise, mind your own damn business!

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89RS w/350 TPI; 69RS/SS w/450 HP 350/Muncie 4-Speed "Too weird to live, too rare to die."

Pro Built Automatics

If you can "manually" shift it ok, and the shifting in the "D" position causes some slippage, then the main line pressure is down. The easy solution (for now) is to install a .500" main boost valve. This will raise line pressure in the "D" or the "OD" position. I would add the .296 intermediate/reverse boost valve while in there. This will help with the manual 1-2 shifts. You could add the Corvette servo, which in turn will help out 2nd & 3rd gear shifts at all throttle openings. Both of these are easy to do, and will "improve" the overall situation. I have these parts in stock. Dana

iroc2121

thank you for the info. also i just found out as of yesterday that now when i manually shift it minorly slips. it the valve is the problem still... how much would you sell those parts for?

Pro Built Automatics

Go to https://www.700r4l60e.com/store/prod...&cat=52&page=1 This will give you the .500" main boost valve, .296" intermediate/reverse boost valve, and the Corvette servo. Dana