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700R4 no forward, reverse works

This is a discussion on 700R4 no forward, reverse works within the Technical / Maintenance forums, part of the General Discussion category; Hey folks, I searched the previous threads looking for answers, but didn't find a situation quite like this. Also, I'd ...

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    Exclamation 700R4 no forward, reverse works


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    Hey folks, I searched the previous threads looking for answers, but didn't find a situation quite like this. Also, I'd like to commend all of you on providing some great advice. This is a great site, I'm glad I found it. I've read a lot of the posts here while looking for answers.

    Second, maybe you can point me in the right direction. I have an 87 Chevy 1500, 350 TBI with a 700R4. Driving down the highway, I lost overdrive, about two miles further, I exited and once I stopped, I had no forward gears at all. Running through the gears manually does nothing and the trans isn't making any strange noises. I looked under the truck and fluid was leaking just behind the torque converter. I checked the fluid level and it was empty, I added fluid, but still nothing, except reverse. Reverse works but that's it. Looking back on the highway, there was evidence of something happening. Right about where I lost overdrive, there was a large spot of trans fluid, then a steady trail up to where I stopped. The trans will now leak, but only if the truck is running and then only if I,m moving it in reverse. Before I tear into this trans, does anyone have any ideas on what I should look for? Any advice will be greatly appreciated. Thanks!

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    D to the MAX gr8shot's Avatar
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    Re: 700R4 no forward, reverse works

    did you fill the tranny back up to full? or did you just put a quart in it? It won't go without any fluid in it. On my old truck the dipstick tube randomly popped loose and leaked like crazy. That was about 5000 miles after a rebuild. Before that when it was goind out, it would just barely creep into drive or reverse, so who knows, maybe yours died. All it took for my leak though was a new O-ring. See if you can pinpoint where it's leaking, and let us know. That might help some.

    When my 700R4 went out on my 92 I have now, I still had all my gears, but it wouldn't shift til I hit the redline in every gear, and it would chirp the tires going into second cuz it shifted so damn hard. So I don't think yours is dead.
    04 Chevy LB7 Dmax. Exhaust, Intake and EFI Live from Husker Diesel

    SOLD!!!! 07.5 Chevy LMM Dmax DPF Deleted, EFI Live from Husker Diesel & more 448hp/834tq

    1992 Chevy 1500 ECSB 4x4 350TBI 320k miles

    '95 Chevy 2500 ECLB swapped in a 95 12v cummins, NV4500, 2wd

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    Loves GMT400 haters someotherguy's Avatar
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    Re: 700R4 no forward, reverse works

    If you can't get any forward gears at all, all you have is reverse, the forward clutch/forward sprag assembly are most likely toast. Reverse is the only gear that doesn't use the forward clutch and everything except 4th and reverse use the forward sprag assembly.

    Full speed down the highway with a suddenly empty pan pretty much spells disaster for your transmission.

    Richard

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    Re: 700R4 no forward, reverse works

    Thanks for the quick reply. I did fill the tranny back to full right after it happened. I figure I'm gonna have to rebuild the trans. I haven't done it before and I'm not sure what to look for once I get it apart. Could a broken seal cause this problem? The trans didn't leak until this incident. I'll try to get a better look at where it's coming from. The truck has a 6 inch suspension lift and 35's so it's pretty easy to get under :)
    Thanks again for the advice!

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    D to the MAX gr8shot's Avatar
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    Re: 700R4 no forward, reverse works

    Well I'm not a tranny expert, but I'd think that if it was a seal that broke, and was letting the pressure out of the lines, then there's a chance that if you replace the seal then it mite be fine. Sounds like 'someotherguy' knows more about trannies than I do though.
    04 Chevy LB7 Dmax. Exhaust, Intake and EFI Live from Husker Diesel

    SOLD!!!! 07.5 Chevy LMM Dmax DPF Deleted, EFI Live from Husker Diesel & more 448hp/834tq

    1992 Chevy 1500 ECSB 4x4 350TBI 320k miles

    '95 Chevy 2500 ECLB swapped in a 95 12v cummins, NV4500, 2wd

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    Re: 700R4 no forward, reverse works

    no pressure builds heat and cakes parts...try to replace the seal if its external. internal take it to a shop to many things you can do wrong..

    good luck pulling the trans out they are a bear..lifted trucks suck when engines or transmissions break...
    Last edited by trickedout420; 10-09-2008 at 08:21 AM.

 

 

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