sqlguy

I changed the transmission fluid the other day. Sounds simple enough. I have a 1979 Vette with a 350 Auto (THM-350 transmission). NOW for some reason, my gears are jacked up. When I tried to back the car out of the garage, it went FORWARD while i was shifted into REVERSE!. Everything does forward now. NEUTRAL EVEN! What in the world happened? All I did is change the filter and seal. I even thought that I must have done SOMETHING
wrong, so I took it all apaert again, and replaced the filter and seal again.. filled it back up with new fluid.... and SAME THING... all I get is forward. I checked the linkage, looks fine, I am really moving the shifting lever into the right positions. This is really driving me crazy, the car is undrivable, all because of a simple tranny oil change. PLEASE PLEASE PLEASE HELP ME!!

Thank you in advance... I am getting desperate. :nopity

-Mark :nonod:


[Modified by sqlguy, 10:16 AM 9/29/2003]

homers3

check that the cable attaching point at the side of the tranny didnt get turned around....or maybe you discinnected the shift cable and hooked it up on the wrong side of bell-crank

sqlguy

Thank you for the suggestion, but I took digital photos of the thing before I took it off... and I am sure that it is on correctly.. there is only 1 way to re-attach the thing. It is impossible to re-attach it incorrectly. I am sure that the linkage is on correctly. I had a friend sit in the car... and shift the gears into the different possible positions, while I sat under it.. and I can see that the shift shaft is moving.. and it is in the correct location (we did this with the car AND tranny pan off). Any other ideas guys??? Come on... I am sure that you guys have seen this kind of thing before... (I HOPE) Tranny was acting fine before the fluid and filter change... it was just leaking badly, which prompted me to replace the filter and seal.

Thanx for the help!!!! I am still sitting with a dead vette.. kinda making me sad... OK.. REALLY MAKES ME SAD!!! :mad

-Mark

blunsford

I had the opposite problem with a power glide once. It turned out I accidentally disconnected a piston from the linkage inside of the tranny. I'm not familiar with the TH350, but I bet it's something similar.

SharkPilot

Hi,
Just wondering. Is it possible that a small piece of dirt got into the valve body, while the filter was off? Those valves in the valve body have such small clearances that even a tiny dirt or matallic particle could cause one to stick. If one of those valves was to get stuck, who knows what could happen.
You might try removing the valve body and flushing it out. But be careful, there are check ***** and such up in there. Get a good trans or factory service manual before you try that. I put a shift into my old T-400 and it isn't too bad to work on. Just intimidating, and dirty too, but you know that already.
I know you don't have reverse, but don't drive the car. With a problem like that the trans may have clutch packs dragging. Driving the car could burn up the trans quickly.
Good luck and I hope you get it solved.

SharkPilot :steering:

jerryp58

I don't think there is such a thing as a "simple tranny oil change" on an older transmission.

I'm sure you've triple checked the fluid level by now.

My first guess would be some "grit" is stuck somewhere in there making a valve or something stick, but you may want to look through the B&M Shift Improver Kit installation & troubleshooting pages here... http://users.erols.com/jerryp58/corvette/bnmkit.htm Specifically, check the action of the "S" link and detent.

I guess your 350 could be a little different from mine, but maybe there'll be something useful in there.

If all else fails, I might try a power flush/wash, but you may want to open the valve body, clean everything up, and maybe even put a shift improver kit in there while your at it. But I'm sure you'd like to get the thing working correctly first before you make any modifications.

Sorry I couldn't be any more help. Good Luck.

Smokehouse69

I think it is the shift cable, if the TH350 is anything like the TH400, you have to disconnect the cable mount bracket when you pull the pan. I guess that you have something slightly out of place when you bolted it back up.

sqlguy

Thank you very much for the rapid response!!! I think you might have something with the "S" link... I do remember that it did cause me a bit of confusion... I looked at the link that you sent, very cool.. BUT.. the images are almost unviewable.. I can't make out the "s" link.. I do not know what the proper position for it. Any insight into that?? Does anyone have a clearer picture of a properly positioned "S" link clip??? I actually remember mine falling off during my fluid change.. and I replaced it.. into (what I thought was) the only possible position. I must have made a drastic mistake.. but I can't find anything online or elsewhere that will help me understand the proper position of the damn thing... this is killing me.. it has been 3 weeks now since I have enjoyed the quality time with my "baby"...

thanx for the continuing help!!!

-Mark

jerryp58

I think this is the book I used in addition to the B&M instructions... http://www.engineering-shop.com/Turb...895860511.html

I was able to get it from the local library which borrowed it from a local community college.

If I remember correctly, the S-link placement wasn't intuitive and it took a couple of tries for me to get it placed correctly and the linkage movement correct. There may be some written description in the B&M instructions that may be helpful. You may want to search the Web for -- "S link" th350 -- also.

Wish I could be more help. If you can't find anything let me know and I'll see if the library can get the book again so I can scan some pics.

Marc80

I can probably snap you a digital photo of my 1980 today after work. Am I correct in assuming that you are looking for a shot of the area where the cable links to the transmission?

Marc

jerryp58

Mark,

I tried to do a little better scan on the pics. It's not great but maybe it'll help...

http://users.erols.com/jerryp58/corv...emp/trans1.jpg
http://users.erols.com/jerryp58/corv...emp/trans2.jpg
http://users.erols.com/jerryp58/corv...emp/trans3.jpg
http://users.erols.com/jerryp58/corv...emp/trans4.jpg

It may help to read all of the instructions too. There are a few places in there where it talks about the fit of the S-link, the detent sprint & roller, and the operation of the inner selector lever.

Don't give up, you'll figure it out :thumbs:

Oh, I don't know if it'd make a difference, but if the hole the S-link goes into goes all the way through the manual valve, you may want make sure you didn't somehow turn the vavle 180 degrees in the body. I don't know if it's symetric or not. Just something to check.

Jerry


[Modified by jerryp58, 7:12 PM 9/30/2003]

sqlguy

WOW Guys... I am amazed and grateful that you all are sooo helpful!

Thank you for the scans!!! I am reading them now... I know that I
have something wrong... I took some digital pics a few minutes ago,
and it does not look like your scans. Does the "S" Clip go both in
the valve and the bracket connected to the shift shaft? See my pics
below to see where the "S" clip is sitting now... No wonder I get no
action with the thing.. must not be shifting at all...

http://test.abadonstudio.com/images/DSCF0001(Small).JPG
http://test.abadonstudio.com/images/DSCF0002(Small).JPG
http://test.abadonstudio.com/images/DSCF0003(Small).JPG
http://test.abadonstudio.com/images/DSCF0004(Small).JPG

Is the Manual valve supposed to be all the way into the body, or is it
supposed to be out and sliding?

Thanx again for all of your help!! I smell driving time coming SOON!!!!! :auto:

-Mark

sqlguy

Ok, I think I know what happened...

I just got finished putting the thing back together... I think I have
the "S" clip on correctly now. I took some pictures of it, what do
you think? Does it look right...?

http://test.abadonstudio.com/images/DSCF0006(Small).JPG
http://test.abadonstudio.com/images/DSCF0005(Small).JPG
http://test.abadonstudio.com/images/DSCF0004(Small).JPG

I have to buy a new tranny pan now though, I kinda screwed this one up
trying to put a drain plug into the thing.. Anyone know where to get
one for a good price? Preferably with a drain plug??? Any advice
there would be appreciated. I think it is all I need to be running
strong...

Thanx a ton for all the help!!! I have submitted questions to other
forums and never got any answers... This is my new home... Thank you
all for making me feel welcomed!!!

-Mark

jerryp58

Mark,

Looks good.

You should get someone to shift from P to 1st while you're watching the action to make sure there's no interference or other problems.

Hopefully, you'll be back on the road soon :steering:

You can pick up chrome pans with drain plugs for probably around $35 from some of the vendors listed here. Everyone sells parts for the TH350s.

And by the way, Welcome to the Forum :seeya