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Technical TH350 lost third gear - binding?

Discussion in 'The Hokey Ass Message Board' started by snod83, Jul 28, 2020.

  1. snod83
    Joined: Mar 28, 2014
    Posts: 18

    snod83
    Member
    from Indiana

    So I was driving my T-bucket today and had something odd happen. After a 40 mile drive in the morning with no troubles, I went to head home and on leaving town lost third gear.

    By lost, it isn't like it slipped though. When it shifted it is like someone put the brakes on. It is almost like the trans is in a bind in third. I only let it try for just a few seconds.

    Some more background, this trans has been in the car for 15 years and I have never had any trouble.

    Any thoughts???
     
  2. Jmountainjr
    Joined: Dec 29, 2006
    Posts: 1,672

    Jmountainjr
    ALLIANCE MEMBER

    Perhaps broke an anchor end on the band?
     
  3. potshot
    Joined: Jul 15, 2005
    Posts: 70

    potshot
    Member
    from MT

    Does it make a 1-2 shift at the normal road speed? If it does, but won't shift into third, it's probably an internal problem. If it doesn't want to make a 1-2 shift at the normal road speed, check vacuum to the modulator or the plastic governor gear.
     
  4. greybeard360
    Joined: Feb 28, 2008
    Posts: 2,074

    greybeard360
    Member

    Does reverse still work?
     

  5. snod83
    Joined: Mar 28, 2014
    Posts: 18

    snod83
    Member
    from Indiana

    Reverse works great and the transmission works perfectly normal until it tries to shift into third.

    It seems like it is going to eat itself when it shifts into third, so I drove home in second!
     
  6. squirrel
    Joined: Sep 23, 2004
    Posts: 55,931

    squirrel
    Member

    sounds to me like it already ate itself.

    Does a broken intermediate roller clutch race do that? I forget...it's been a while
     
    da34guy likes this.
  7. greybeard360
    Joined: Feb 28, 2008
    Posts: 2,074

    greybeard360
    Member

    Only thing I can think of is the intermediate sprag is damaged. Not real sure because it is supposed to freewheel in reverse and 3rd.
     
    VANDENPLAS likes this.
  8. What Squirrel said ^^^^
     
  9. snod83
    Joined: Mar 28, 2014
    Posts: 18

    snod83
    Member
    from Indiana

    So these roller clutch things - are they something that normally wear, or just break?

    I am not going to lie, I don't mind stuff breaking when I horse it, but I was actually gingerly leaving town when this happened and it was like a light switch. Zero issues before this.
     
  10. squirrel
    Joined: Sep 23, 2004
    Posts: 55,931

    squirrel
    Member

    Welcome to automatic transmissions. Sometimes it takes a while for damage to show up.
     
  11. A sprag clutch broken down to its individual pieces is nothing more then an inner and out race with either ball bearings or Tomken bearings , and springs.
    When I first saw one apart I was shocked at how strong they are assembled and working correctly.

    but like @squirrel said , once they wear it one part fails it’s pretty much catastrophic failure of the part.
    Hopefully no other damage to the trans.

    A th350 is a pretty cheap and easy trans to rebuild.
     
  12. squirrel
    Joined: Sep 23, 2004
    Posts: 55,931

    squirrel
    Member

    Lots of guys call any one way clutch a sprag..but many of them are actually roller clutches. The only one that's an actual sprag, with dogbone shape locking members, was used on early transmissions, as well as the later 4L80E, but not the TH350. You can tell the difference easily, roller clutch has flat accordion springs and round rollers, and one race is notched, while a sprag has both races smooth, and there are no accordion springs.

    sprag.jpg

    no biggie, just another one of those wording pet peeves.
     
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  13. 56sedandelivery
    Joined: Nov 21, 2006
    Posts: 6,695

    56sedandelivery
    Member Emeritus

    What's the fluid look like; burnt or particulates? Have you pulled the pan? Any metal pieces in the pan, and the trans has to come out for a rebuild. I am Butch/56sedandelivery.
     
  14. Ericnova72
    Joined: May 1, 2007
    Posts: 595

    Ericnova72
    Member
    from Michigan

    Normally, when the TH-350 roller clutch blows up, all you lose is 2nd gear...it becomes a second neutral and just freewheels in 2nd gear, but 1st and 3rd continue to work just fine.

    The 2nd gear roller clutch(intermediate "sprag") is contained inside the tin cover on the back of the intermediate drum....I've driven home 70 miles from the drag strip with the roller clutch blown and not killed the trans. Just have to pull it down. clean it out, and put a new drum and sprag back in.

    I'd say you've got some issue other than the roller clutch/"sprag" problem, other than the possibility it broke the outer sprag race and pinched the pieces in the intermediate frictions spline maybe....I've not seen that happen.

    Regardless, sounds like it ha to come out and your gonna have to get inside of it deep.
     
    Baumi likes this.
  15. Kevin Ardinger
    Joined: Aug 31, 2019
    Posts: 778

    Kevin Ardinger
    Member

    One way clutch holds in second overruns in third so the whole gear train turns as one unit. I would possibly suspect a cross leak in the valve body like a ball blown thru the plate applying two clutches at the same time.


    Sent from my iPhone using The H.A.M.B. mobile app
     
  16. 56sedandelivery
    Joined: Nov 21, 2006
    Posts: 6,695

    56sedandelivery
    Member Emeritus

    I was thinking the trans might have been "jumping" from first to third, because of a scattered intermediate roller clutch sprag race, and him thinking it just was't making it to third gear by the count (1,2,3 but 1,3 and skipping over 2). Now we have to wait and see. I am Butch/56sedandelivery.
     
  17. Baumi
    Joined: Jan 28, 2003
    Posts: 3,043

    Baumi
    ALLIANCE MEMBER

    I´ll second this^
    I blew up the "sprag" in one of my TH350s and it kind of skipped second, drove fine in 1st and 3rd...
    Maybe you´ve got a leak in the valve body or a blown o ring, which allows oil pressure into 3rd and reverse circuit at the same time. I don´t know if that´s even possible, but what you are describing sounds like a trans brake would be applied....
     
    Atwater Mike likes this.
  18. snod83
    Joined: Mar 28, 2014
    Posts: 18

    snod83
    Member
    from Indiana

    Alright, so now we might be getting somewhere. I am positive it is not skipping second to go to third due to the RPMs it is turning at road speed. Normally I am at 1600 at 55, now it is 2500 or so.

    It kind of "feels" like a transbrake. It doesn't grind or make noise, it just grabs. Is there a specific cross leak that I should look for in the valve body to diagnose this?

    Fluid looks good and clean, smells like celery (personal opinion) not burnt. I have not dropped the pan. Currently the car is still mobile and I don't want to immobilize it without further research and investigation.
     
  19. squirrel
    Joined: Sep 23, 2004
    Posts: 55,931

    squirrel
    Member

    Drop the pan and see what you have....
     
    Baumi likes this.
  20. Baumi
    Joined: Jan 28, 2003
    Posts: 3,043

    Baumi
    ALLIANCE MEMBER

    ^this, and take a pic for us of what you see...
     
  21. 427 sleeper
    Joined: Mar 8, 2017
    Posts: 2,865

    427 sleeper
    ALLIANCE MEMBER

    I'm curious, please don't take this as an attempt at a diagnosis, but if only third gear is gone, wouldn't that be somewhere in the direct circuit? Possibly one of the ring's on the pump? I need to learn more about these thing's. Please explain, as I am eager to learn! :D
    P.S. Sorry for the Hi-Jack.
     
  22. squirrel
    Joined: Sep 23, 2004
    Posts: 55,931

    squirrel
    Member

    Third gear isn't gone. What's probably happening, is that another gear is not releasing. It could be 1st, 2nd, or reverse. it's been a while since I had to remember what is engaged in what gear...perhaps knowing how the transmissions behaves in reverse and in manual low and manual second will help us figure it out. Or another gear is engaging when it shifts into 3rd.
     
  23. snod83
    Joined: Mar 28, 2014
    Posts: 18

    snod83
    Member
    from Indiana

    So low one puts it into first, low two starts off normal and shifts to 2nd without any trouble. Reverse works fine as well. Any other ideas for tests?
     
  24. 31 Coupe
    Joined: Feb 25, 2008
    Posts: 383

    31 Coupe
    Member

    Not a TH350 expert but what would happen if the 2nd gear roller clutch (sprag) locked on permanently, would that allow 1st gear to operate normally but cause the sudden "binding" that he's experiencing on the 3rd gear upshift?
     
  25. justpassinthru
    Joined: Jul 23, 2010
    Posts: 524

    justpassinthru
    Member

    Does the car creep backwards when shifted into reverse, when you take your foot off the brake, or do you have to give it some gas to get it to move backwards?

    Reason I ask is it's possible that the 2-3 accumulator piston could have broke the center out of it and then it applies the intermediate band from the 2-3 accumulator spring.
    The intermediate band is only used during passing gear, for additional holding power and in manual 2 for engine braking. The band is not very substantial and will slip with the taller reverse ratio, and the car will back up, but will also feel kinda like something is binding also. It does not take a lot to overcome the band and make it slip.

    The 2-3 accumulator piston and the intermediate band servo piston are located in the same bore. Many TH350s and TH400s had plastic 2-3 accumulator pistons, that would break.

    If the intermediate roller clutch were exploded and virtually welded together, when the car shifted to 3rd, it would literally lock up the trans internals, until one of the clutch packs failed.
    Sorta like if you had a manual trans in 2 gears at the same time. It would come to a screeching halt until it shifted back out of 3rd.

    If it feels like the brakes are dragging when in 3rd gear or in reverse, but are able to overcome it and still move with more gas, I suspect the accumulator piston problem. You would have to removed the valve body to find out.

    Bill
     
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  26. Atwater Mike
    Joined: May 31, 2002
    Posts: 11,625

    Atwater Mike
    Member

    Guess what I'm gonna think about the next 5 salads...:eek:
     
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  27. greybeard360
    Joined: Feb 28, 2008
    Posts: 2,074

    greybeard360
    Member

    I was looking in my old Motors auto trans manual trying to figure out what could be going on. The way the clutches apply in sequense had me scratching my head about what could be going on. The only cluches not applied in 3rd are the low/rev clutches and not sure if a check ball blow thru could cause them to apply in 3rd or not.
    Over-runnung clutch, sprag, one way clutch and then Ford decided a few years ago to start calling the "mechanical diodes"..... go figure.
     
    VANDENPLAS likes this.
  28. inthweedz
    Joined: Mar 29, 2011
    Posts: 580

    inthweedz
    Member

    I know what I'm about to explain isn't top gear, but a while back, my friend lost reverse in his T350..
    When we pulled in down, turned out the large circlip in the body, holding the reverse clutch assy had popped out of the groove..
    Could it possible be the same problem here?? Maybe one of the 3rd gear clutch's circlips has let go..
     
  29. snod83
    Joined: Mar 28, 2014
    Posts: 18

    snod83
    Member
    from Indiana

    Alright guys - I'm not intentionally delaying progress here, but I haven't gotten back to the bucket yet. I did pick up a shift improver kit (easy way to get valve body gaskets) and plan to drop the pan to install it. I'll update this thread when I get the pan off.

    Thanks!
     
  30. saltflats
    Joined: Aug 14, 2007
    Posts: 12,592

    saltflats
    Member
    from Missouri

    Please say you didn't buy a B&M kit.
     

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