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Hot Rods A different kind of 700r4 4th gear question...

Discussion in 'The Hokey Ass Message Board' started by applekrate, Jul 21, 2018.

  1. Have searched through the board files on 700 trans issues, etc. There seem to be several concerning people not having 4th gear but, they all seem to be related to new swaps. Either the trans has no miles on it, someone did not install the TV linkage adjustment correctly, etc, etc.

    The difference here is I have had the 700 in my car for several years and it has been performing well. I often tow my boat, car trailer or tow dolley with my 700r4 equipped GTO. I know not to use 4th while towing and have a large separate trans cooler.
    Anyway, about a month back 4th gear just went away. I have been driving it since with over a thousand miles since 4th went away ( it is my primary transportation ) with another 500 tomorrow.

    Questions from those with experience please-
    1 why may this have happened?
    2 am I ok to continue driving/using the car without 4th gear?
    3 Am planning a road trip in a week or so to the midwest from Az and will be towing a car to Ohio and do not want to have trans issues. I can live without 4th gear as I run 2 series rear ratio.

    Am estimating 50,000 miles on the trans. have never used the lock up. Trans has never been hot. Fluid is not burnt.

    Reverse, 1st, 2nd and 3rd work fine.

    Would appreciate any help from those in the know.
    chryslerfan55 likes this.
  2. dogwalkin
    Joined: Jan 17, 2013
    Posts: 91

    from tn

    I put a 700 in my 64 gmc. It had been rebuilt and never used. I had No 4th gear no matter what. Otherwise it was perfect. To make a long story short the seal on the servo that applies 4th gear was broken.

    Its easy to check and fix if thats the problem. You can always add a corvette servo too.

    Sent from my VS996 using The H.A.M.B. mobile app
  3. Will I get in trouble if I post a link to about exact same issue with my 700R4?
  4. Go there and do a search on "49fordcoupe" and you will find it.

  5. '49 fordcoupe- thanks for the link. I did try it and found some info there but, nothing was conclusive. I did not see a problem solved, just discussions about possibilities.

    Would anyone else with experience who know what they are talking about- know why a 700 trans would loose 4th gear? This is not a new or rebuilt trans. Not an install with a few hundred miles. I have well over 50,000 miles on it and I tow with it often.

    I do think it being low on fluid did have something to do with this problem and hoping that 'clue' will help find the problem.

    1. wanted to learn what the problem is
    2. wanted to know if it is OK to keep using the trans without 4th? will it effect reliability? Am planning a drive to the midwest soon, probably 4-5,000 miles. If 4th cannot be easily repaired, am I ok driving it on this trip with 4th gear ( mileage and engine rpm aside ).? is the best way to make repair?

    thanks much
  6. Hey Apple.. is there any possibility that the symptom is temperature related?.. I don't remember you saying one way or the other... Mine is definitely temperature related.. for the first few miles, when "cold"...103 in Austin.. it's fine, once "up to temperature".. that's when 4th disappears.. did I mention that I just bought a Sonnax 2 and 4 servo just for the heck of it...$176 bucks on Summit...... can't hurt.. and I noticed that my Corvette servo seemed a bit loose .. there is a short video on my the transmission rebuild either the Chapter one or chapter two.. don't remember..
  7. You may already know this, but 3rd gear is "direct" and actually should be less stressful than 4th "overdrive".. It shouldn't hurt a bit if you don't mind the gas mileage..
  8. The thing about the servo is that you don't even have to pull the pan to replace/repair the servo. And if you chose to put a Corvette or Sonnax servo in there, it surely cannot hurt and might even fix if your o-rings have gotten screwed up in your servo.. just thinkin' out loud...
    dogwalkin likes this.
  9. Hey, Apple.......just curious.. why have you never used lockup ???

    By the way, my symptom popped up the first time I found that I was low on fluid - had a leak on my trans cooler connection up in the grill and didn't notice the "pool" under the front of the car for a while. But it worked perfectly until I ran it hot (nearly boiled over) and low on fluid at the same time. If it was sucking air, then the cooler wasn't doing it's job either, and maybe the trans overheated, which would put more stress on all the o-rings and pressurized devices that depend on the o-rings and d-rings in the transmission, which might explain "blowing a seal".... if in fact that's what happened to mine.....hmmmm

    It's still tooo dang hot to get out there and put in my new Sonnax 2/4 servo. supposed to be 108 today... grrrrr
    Last edited: Jul 23, 2018
  10. 49 Ford coupe- I do not think it is temp related. Yesterday, I spent some time with someone very knowing on trans. I got a new 4th servo, Corvette style. He showed me how to install it and how to check the parts on my trans for something worn, or broken.
    I drove the car another 550 miles in the last day and a half with no issues other than no 4th gear.
    Am thinking it best to take apart a core trans or 2 ( servo area ) to familairize myself better with them before I work on my own trans as this is primary transportation for me.
  11. Yes, 3rd is direct. I was taught to only tow in 1-3 gear, not to use 4th. My car uses a 2 series rear gear so, not bad without the 4th though I really like seeing the revs going low. My torquey Poncho, with its larger stroke, is happy with the taller gears than a chev would be. Still, would like that 4th working again.
  12. My Poncho normally runs a 455 but have a smaller 389 in it now. With the 2 series rear gear and the OD, the engine is not 'happy' using the lock up. Vacuum and mileage is less using the lock up.
    '49 Ford Coupe likes this.

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