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Old 02-12-2009, 11:05 AM
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Muncie truck tranny shifter popped out of place?

I have a 1990 Chevy C3500 dually,that I was trying to maneuver a trailer with, in a tight spot yesterday.I was rapidly shifting from 1st to reverse to go back and forth(no grinding involved) when the shifter felt funny and I couldn't get it in reverse anymore.

I'm pretty sure its a Muncie sm465 4 speed like all of my earlier Chevys,the shifter comes out the same way.

About 10 years ago,in another Chevy,same type tranny,the clutch started to go and the shifting became real hard.I double clutched and tried to force it into the next gear,when the shifter began to swim around like it wasn't connected to anything.Pulled over,popped the shifter,aligned the shift rails to neutral with big screwdriver,popped shifter in,put it in gear and away I went,no problem.Yesterday,the shifter didn't become totally disengaged.

After yesterday,I popped the shifter,played around aligning the shift rails,found what I thought was neutral,but all I can engage is the Granny gear and 1st.Can't get top two gears or reverse.Shifter handle doen't move to the right enought to grab reverse or the top gears.Played with rail alignment some more,no help.

Any ideas?
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Old 02-12-2009, 04:08 PM
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Quote:
Originally Posted by Barrybomb
I have a 1990 Chevy C3500 dually,that I was trying to maneuver a trailer with, in a tight spot yesterday.I was rapidly shifting from 1st to reverse to go back and forth(no grinding involved) when the shifter felt funny and I couldn't get it in reverse anymore.

I'm pretty sure its a Muncie sm465 4 speed like all of my earlier Chevys,the shifter comes out the same way.

About 10 years ago,in another Chevy,same type tranny,the clutch started to go and the shifting became real hard.I double clutched and tried to force it into the next gear,when the shifter began to swim around like it wasn't connected to anything.Pulled over,popped the shifter,aligned the shift rails to neutral with big screwdriver,popped shifter in,put it in gear and away I went,no problem.Yesterday,the shifter didn't become totally disengaged.

After yesterday,I popped the shifter,played around aligning the shift rails,found what I thought was neutral,but all I can engage is the Granny gear and 1st.Can't get top two gears or reverse.Shifter handle doen't move to the right enought to grab reverse or the top gears.Played with rail alignment some more,no help.

Any ideas?
If I remember correctly the stick loads into the tower from the top and is retained with a lock ring. This lock ring should be under a small rubber boot around the top of the shift tower but if not the boot is insignificant. Use a pair of channel locks to grab the lock ring and push down while turning to the left about a 1/2 of a turn. After you do that the stick should pop out. The shifter should have a big ball made into it that sets in the tower. You have probably broken something in the top of the tower. Maybe a pin or a bushing and I think that there is a spring under it that holds pressure up against the ball. This ball should have a groove down one side and a pin should be in the top of the tower and it fits in the groove to keep the shifter from rotating. I have seen these pins break and wear down letting the shifter rotate. Check the groove for wear and also check the bottom end of the shifter and shift rails for wear.

On the off hand the shifter may go up through the bottom of the shift tower (transmission top cover) and the retainer ring could be up in there. The only way to see it is if you remove the shift tower and turn it upside down and look. In your post you didn't say how you removed the shifter and I can't remember for sure if the year and transmission that you have goes in through the bottom or top of the tower.

The other problem that you speak of is that you probably don't have all of the shifter forks and rails lined up in the neutral position. Make sure the truck is on level ground with blocks under the front wheels. If there is any tension on the rear wheels it will hold it in gear and keep you from getting it into neutral. You may have to get someone to get under the truck and rock or twist the drive-shaft back and fourth to get it into neutral while you push on the shift rails. When you reinstall the shifter make sure that all of the rails are in the neutral position. When they are all lined up it will make like a little rectangle box for the end of the shifter to fit into. Now the tricky part is getting the end of the shifter to go into the little rectangle box that is made when all of the shift rails are lined up and in the neutral position with out popping out. Its a guessing game because you are doing this blind. If you do have to remove the shift tower then basically do the same thing. When you do get it in the right place hold pressure on the shift tower and put a couple of bolts in it to hold it until you can get the rest of them in.

Good luck and I hope this helps.
Chris
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Old 02-12-2009, 05:13 PM
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Chris,thanks,you described it better than I could have.

It seems to me that I was able to get the rails lined up in the neutral position.I am able to find neutral,granny and 1st.I believe I have the shifter in the hole formed when the rails are lined up in neutral,when you land the handle there it drops in and the ball seats into the socket and pins on the tower.I then am able to set the spring loaded retainer in place and shift gears,but only neutral, granny and 1st.I can drive it in these gears.

I can feel the spring loaded ball on the end of the stick(inside the tranny) in neutral when I rattle the stick.It just seems that I have lost stick travel to the right side(when it's in your hand) to enable a shift to the higher gears and reverse.I can see the rails and spring loaded ball when looking inside.It seems that the ball only wants to move only so far to it's left.Maybe there is a photo somewhere looking down into the rails somewhere I can compare to to know if something isn't right.

I've always had to fight for reverse by double and triple clutching this tranny and hitting reverse.
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Old 02-12-2009, 05:52 PM
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Low and first gear are on the same shift rail and that would be the rail that is the farthest away from the driver. The middle rail is second and third (high) gears. The rail that is the closest to the driver is reverse. There is a posibility that one of the shift forks is bent or either slipped on the shaft. If I remember right there is a roll pin that goes through the shift rail and fork and that is what holds it in the correct position on the rail. This pin could be broken or sheared or the fork could be bent. Just the fact that you can drive it leads me to believe that all of the forks are going into the neutral position and not locked in gear but the rail is not going into the neutral position. If you can not get the shifter over to the second and third gear rail then there is some reason that the center rail is not coming all the way back to the neutral position. The end of the shifter is bumping against the edge of it when it tries to leave the first and low rail. I know that you don't want to hear this but you may have to pull the top cover (shiftower) to see just what is going on in there.

I don't have a diagram of this on hand but sit tight as I'm sure that someone else up here does.
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Old 02-12-2009, 09:06 PM
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Chris,you are pretty much on the money with everything you have said.
I greatly appreciate your call for help on my behalf.
I did a little internet search and found something that may answer my question, a slideshow of the Muncie,with one having a view down the shifter hole,check it out here,scroll down tothe bottom of the page

http://www.novak-adapt.com/catalog/sm465_package.htm

Kind of a PIA that I can't stop the slideshow on the photo,but from what I can see...the spring loaded button(the one you press against to put the shifter in reverse) has come apart in mine.I can see the button and the spring(that I guess is supposed to be self-contained inside the button) when I look inside my tranny.I wasn't sure that the spring itself wasn't supposed to be visable.I'm thinking that the shifter is not able to compress the button over to it's left enough to engage 2nd and 3rd let alone reverse.

So,what is the part called and how do I change it? Luckily,I have a large enough access cover in my floor board to be able to remove the tranny tower rather than having to drop the tranny.
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Old 02-12-2009, 10:16 PM
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Yeah that's the reverse lock out pall. It is basically a pin with a spring behind it to keep you from accidentally bumping the the shifter into reverse when you shift from first to second gear. This may be why you have had problems going into reverse before this incident. It is made into the shift rail so you are going to have to pull the top cover to repair it. It's not that bad of a job just count all of your bolts and make sure you have the same number when you are finished. That way you wont loose anything in the transmission and that could be catastrophic. Unbolt all of the bolts and lift it straight up. When you do get the top off make sure that none of the pieces of the pall have fallen into the transmission. I believe that this transmission has a magnetic drain plug and it should catch any of the small pieces. As a safe gaurd while you have the top off you should drain the transmission and with the drain plug out pour a couple of quarts of parts cleaner through it. I doubt that you will be able to find what you need from a junk yard because they will want to sell you a complete transmission. Although you may be able to find one that has a busted gear or case fairly cheap and you could use the top cover off of it. But if you do wind up at the chevy dealer for the parts, don't to worry it shouldn't cost that much. Your are definitely going to need a brake down to help you understand how the shift rails work with the detent balls and springs that hold them in place. I'm still looking for one and may have something for you in the morning. If you have a chevy dealer close by you might could talk one of the parts guys into running off a copy for you.

Last edited by Chris Kemp; 02-12-2009 at 10:32 PM.
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Old 02-13-2009, 05:08 AM
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Thanks Chris.
I have a GMC dealer nearby that is all about trucks of this size,with some good parts guys there.They should be able to hook me up with the parts and print out one of the cartoons from their book.Hopefully they have it in stock,I want to put it together this weekend.I'll get gaskets too.

Chris,when I pop the top cover,is there anything that is going to want to come up with the cover itself?Is the rail assembly part of the cover itself?It's going to be tight to be able pull the cover straight up,but might be OK.Is there anything that is going to want to drop into the tranny housing as I lift up?

Yeah,I'll plan on draining the gear oil and washing any junk thru the drain hole while I'm at it.I think the last time I changed gear oil in one of these it was about 4 quarts.
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Old 02-13-2009, 05:57 AM
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I just found some online source for the parts,just to show the parts I'm dealing with:

http://www.riversidegear.com/categor...upplies-1.html

Maybe I broke the clip?When I look into the tranny I can see the plunger with the spring on the plunger shaft.Maybe the clip broke allowing the plunger to slide out? I'll pick up the whole thing at the dealer and use only what I need.The plunger and spring may be OK in mine,maybe the clip let loose and caused the problem.The clip I can't see until the cover is off.
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Old 02-13-2009, 08:53 AM
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Other then the pieces to the little pall and maybe the spring or clip for the reverse plunger nothing else should fall into the case. If any of those pieces due happen to drop just fish them out with a long skinny magnet on a stick. There may be some nylon guides on the edges of the shifter forks but usually these don't fall off. Now when you get the top off take it to a bench or table. Its good that you have a reliable chevy dealer to give you a brake down diagram. You could also take the whole cover with you when you go for parts. If you have to remove the shift rail shaft that the reverse fork is on you are definitely going to need a diagram. In the cover there is a series of detent balls that are in a cross drilled passage. The passage is perpendicular to the shift rail shafts. This is how they work: When you have one shift rail in gear these balls keep the other two shift rails from coming out of neutral. They correspond with notches that are machined in the shift rail shafts. They will not fall out when you remove the cover but you have to take them out to remove the shafts. Remember to run some parts cleaner through the case before you put it all back together.

Good Luck
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Old 02-13-2009, 07:09 PM
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Thanks again Chris.
It took some time on the phone,but I found the parts about 30mins away from me.I'll pick them up in the a.m.

Chevy dealer said they haven't carried Muncie parts for years.One truck part shop told me they sold their Muncie stock a while back.A shop that sells parts and does re-builds has it.$40 and it comes with the shifter rail.Seems decent. I have to work tomorrow,don't know if it's a full day or not,hopefully I can do it in the afternoon.If not,it will be Sunday.
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Old 02-14-2009, 07:30 AM
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Forty dollars is a good price! When you pick the part up see if you can pick their brain some on the configuration of the top cover and the shift rails. It's been at least fifteen years since I used to work on these transmissions on a regular basis. I can find everything else but I can't find a diagram of the top cover showing the shift rails. If it was setting in front of me I wouldn't even have to think about it. Muncie, Borg warner, Spicer and New Process all made transmissions that were about the same size and application but each one was a little different. The top cover will either have a set of detent balls or a cross shaft in the cross drilled passage. Either way these will have to be removed to replace the shift rail. Transmissions scare a lot of people but they really are easy to work on. The area that you will be repairing does'nt have any shims or tolerances that you have to set so you don't have to worry about that. Do it on a table so you don't loose any of the pieces. And if you get stuck I'll do my best to help.

Keep me posted.
Chris
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Old 02-15-2009, 06:04 AM
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Hey Chris,picked up the part yesterday,it was an assembly of the detent ball,spring,retainer and attached to the shift fork.Shift fork has about a 3/4" hole in it where it rides on the shift shaft(terminology?) in the cover.Depending on what is easiest,I'll assemble it as is or take from it what I need.I need to check the existing unit to see if the hole where the detent ball seats isn't damaged from trying to jiggle the shifter into gear before I realized the problem.

The one problem I may have,is that with the tranny in the vehicle,I can't really lift straight up on the top cover before hitting something under the dash.We'll see if I can lift straight up a ways then angle out. Dropping it back in is another matter.Is there going to be a trick for landing the shifter forks in place?

Wasn't able to get diagrams at this place,I'm sure the dealer will give me diagrams If I want to make the trip.

Been so busy I didn't realize Monday is a holiday,may put it back a day,family stuff.
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Old 02-16-2009, 02:43 PM
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You shouldn't have any trouble with putting the cover/tower back on. You need to make sure that all of the shift collars are in neutral and that all of the shift forks/rails are in neutral. The shift collars are the round looking spacer things that you will see on the shafts, they are part of the synchronizer assembly. Some people refer to them as clutches or sliders. As long as they are evenly spaced between the gears that they correspond with they are in the neutral position. You do have a little bit of leeway when you put the tower/cover back on and you can wait until after the cover is on to install the gear shift. It should go back together fairly easy so don't force it. If it feels like it is not going back together easy then one of them is not lined up correctly. To keep from tearing the gasket you can glue it down good with high tack or weather strip adhesive on one side. If you use weather strip, use it sparingly, a thin coat on one side is all you need. After the gasket is glued down and dry put a thin layer of grease on the mating side, that way it will slide around and not tear as you move the cover around to line it up.

I got faith in you. YOU CAN DO IT, YOU CAN DO IT!
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