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Old 02-25-2012, 02:22 PM   #1
Funrunner99
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Member Since: Dec 2010
Location: Roseville CA
Default HELP!! 1990 ZF S6-40 stuck in reverse!!!

Ok, I have a '90 ZR51 with the ZF 40 transmission with about 95000 miles on it. have owned it for about a year and put 11K on it so far. Anyhow was backing out of the driveway the other morning, after backing up went to throw it in first, thought it had dropped in but when I let the clutch out it was still in reverse. Now the shifter won't go into any of the gates, just stuck in the neutral area and the car is still in reverse. Backs up fine, no noise or grinding, just won't go forward. Have tried with it shut off, running, doesn't matter. The car has a Hurst Billet/Plus shifter, other than that the driveline is stock. Opened up the console and pulled the boot off and everything as far as the shifter seems fine, no loose parts or missing pins that I can tell. Has anyone else had this problem? Does this mean something internal? Transmission has never given me any trouble or signs of trouble. I am planning to replace the clutch soon but that had nothing to do with the trans, just figured the clutch is probably about done with 90K on it.
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Old 02-28-2012, 12:44 AM   #2
Funrunner99
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Ok, not sure what you mean by cogs? The shifter is almost new and the ball on the bottom connecting the shifter to the shifter input shaft looks fine. The transmission is in the car still so I am doing everything through the shifter opening in the top and from underneath. I didn't install the shifter but it has always worked great and everything I can tell all is in place and normal with it. The car already had the 1-4 solenoid bypassed, I have removed the solenoid and the activation pin in case that was locking things up, didn't make any difference, still locked up. I have been told that the reverse gear sometimes siezes on these transmissions, seems hard to believe it would sieze a minute or two after starting it up in the morning. The night before I drove to the movies and dinner, all very easy driving and parked it that night with everything seeming to be fine. I don't think my "throwing it into first" would cause a trans to lock up. Maybe it was a bad choice of words, just meant I shifted from reverse to first. Have been driving/racing sticks of all kinds for 36 years with no troubles except skattering a clutch on a drag car back in the 80's , don't think it was my technique.
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Old 02-28-2012, 05:16 AM   #3
Funrunner99
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Well for one thing your working on the wrong transmission dude, I have a Tremec TKO-600 in my Mustang which uses the type of shifter you're talking about. The shifter & transmission you’re talking about is for the Tremec T-56, used in the C5's starting in '97. If I had a Tremec in my Corvette then I would have known what you’re talking about and already would have done what you suggested. The ZF S6-40 six speed used in all the '89-96 C-4's is what I have in my car. Totally different setup for the shifter than the Tremec's. The shifter hangs off the back of the transmission, outside of the body and connects to a shift selector rod that comes out of the back of the transmission. You can see the shifter assembly in this link; http://www.rsgear.com/technical/diag...ift-lever.aspx The entire shifter assembly is wrapped in a big rubber boot you can see at the bottom of the picture. Everything else is internal to the transmission and is not accessible without disassembly of the transmission. We can argue all day about my technique & my experience, bottom line the shift wasn't forced. Thanks for your help.
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Old 02-28-2012, 09:18 AM   #4
oldalaskaman
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didnt mean to argue, just doin' a little 'bustin' , and I stand corrected, I saw the shifter you posted and went with the most recent one I had worked on, very sorry bout wasting time with the mixup. And you are right about yours, good luck
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Old 02-28-2012, 02:39 PM   #5
Funrunner99
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Hey no problem, that's the trouble with email/forums, you never know where people are headed. I ran across some of your other posts after I posted and kinda figured out you like poking the bear every now and then, sorry if I reacted poorly.

So how did you delete the other messages?? I am not that good with these forum things!

I wish the transmission was a Tremec, I think they are easier to work on than these ZF things. Parts are WAY expensive also, cheaper to buy a new one than rebuild this one, even just for the parts! I have a couple more things to try before I go out and get another transmission, maybe I will get lucky!
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Old 02-28-2012, 03:14 PM   #6
cuisinartvette
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Get under the car and see if the roll pin that goes in the shaft came out.

That ZF is way way stronger than a T56 will be. Try and fix it.

ZFDoc may be able to help you through it too Google it or Bill Boudreaux

Last edited by cuisinartvette; 02-28-2012 at 03:16 PM.
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Old 02-28-2012, 03:15 PM   #7
oldalaskaman
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to delete, there's a button at the bottom of your post that says 'edit' click on that and there's a delete option. on your trans. have your tried taking the linkage off the levers and using a wrench to manually shift. Sometimes you get lucky and a shift linkage rod bent itself or straightened it self over time and takes things out of adjustment. the shifter itself may have something loose in the mech . with those miles not being the original owner, may be time for at least bearings. Like you say though, you can get new or even low mile used cheaper
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Old 02-28-2012, 03:16 PM   #8
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Quote:
Originally Posted by cuisinartvette View Post
Get under the car and see if the roll pin that goes in the shaft came out.

That ZF is way way stronger than a T56 will be. Try and fix it.
excellent
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Old 02-28-2012, 03:16 PM   #9
bill mcdonald
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Since it sounds like you want to play around with the trans a bit, check out this web page.

You can even shoot Bill a question about it.

http://www.zfdoc.com/

I dont know if it would have anything to do with anything, (I am no ZF expert) but the 90 has the reverse lock out thing, on a stock shifter you pull up the plastic collar under the **** to engage reverse. If your after market shifter does not have one... it makes me wonder if something involving this function could have something to do with what your getting

Also read long ago about the powder coating on the shifter ball could cause some sort of issues as well.
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Old 02-29-2012, 05:24 AM   #10
Funrunner99
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Quote:
Originally Posted by cuisinartvette View Post
Get under the car and see if the roll pin that goes in the shaft came out.

That ZF is way way stronger than a T56 will be. Try and fix it.

ZFDoc may be able to help you through it too Google it or Bill Boudreaux
Yeah, I was thinking I need to do that from what I can see on the exploded drawings I have found on the internet. Couple of little pins & bolts & such I need to make sure are all in place. Hard to see with everything in the way. I wasn't planning on switching to a T56, just commenting on the shifter design & such. I have a TKO 600 5 speed in my '68 Mustang that I like very well. Had a Tremec 3550 5 speed before that that worked really well. Friends of mine & I have had good luck with Tremec's.

This trans has worked flawlessly until now, seems strange to have it lock up like this. I have actually already spent over an hour on the phone with Bill Boudreaux from ZFDoc. Sent him an email and he called me last Saturday. Had a ton of information and suggestions, which I am working my way through. He was way cool!!

Quote:
Originally Posted by bill mcdonald View Post
I dont know if it would have anything to do with anything, (I am no ZF expert) but the 90 has the reverse lock out thing, on a stock shifter you pull up the plastic collar under the **** to engage reverse. If your after market shifter does not have one... it makes me wonder if something involving this function could have something to do with what your getting

Also read long ago about the powder coating on the shifter ball could cause some sort of issues as well.
Bill talked about this also, he doesn’t think it is an issue unless I was trying to push it into reverse while driving forward and wiped out the syncro’s. He also recommended removing the 1-4 solenoid and removing the little pin that gets pushed into block. I already had the solenoid electrically bypassed but went ahead and removed it and the pin, didn’t fix anything. Have also heard about the powder coating, will check that out. Thanks.

Quote:
Originally Posted by oldalaskaman View Post
to delete, there's a button at the bottom of your post that says 'edit' click on that and there's a delete option. on your trans. have your tried taking the linkage off the levers and using a wrench to manually shift. Sometimes you get lucky and a shift linkage rod bent itself or straightened it self over time and takes things out of adjustment. the shifter itself may have something loose in the mech . with those miles not being the original owner, may be time for at least bearings. Like you say though, you can get new or even low mile used cheaper
Cool, will have to use that if I post something I don’t like later! I am going to try taking the shifter off of the input shaft and see if I can get it to loosen up. The “forks” are all internal and can’t get to them without pulling the trans apart. If none of this stuff works then the last resort is to pull the small cover at the rear on the drivers side of the trans and remove what I believe Bill told me is the reverse shaft and take the gear that is under that small cover out. This will disable reverse but he has had success getting the rest of the trans freed up that way. I will have all the forward gears, just no reverse. I will at least be able to drive the car while I wait for my new transmission to get here. Just have to be careful where I park! LOL

Thanks for all of the suggestions.

Last edited by Funrunner99; 02-29-2012 at 06:55 AM.
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Old 01-19-2014, 06:13 PM   #11
Funrunner99
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Well I guess better late than never to post a follow up After trying some of the things Bill Boudreaux/ZFDoc told me to do I ended up buying a new transmission. I sent the new transmission to Bill in AZ and had him do his "balancing/blueprinting" magic to it. After Bill was done I installed the new transmission with a SPEC SFI aluminum flywheel with a SPEC Stage 2 clutch. The car runs & shifts great although I do get the rattling noise everyone is talking about. It's really pretty minimal and actually I kind of like it so it's not a problem. Anyhow Bill was a huge help and the car is running great! That's about it! Thanks to everyone for all of their help and input!!!
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Old 01-19-2014, 06:13 PM
 
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