My rebuilt transmission on my frame off with 25 miles developed a rumble in nuetral, definetly coming from within the case, the transmission ended up on the workbench again and the 4th gear synchro had chunks of brass off of the three tabs which put a bind on the 3rd gear synchro. What caused the chunks to come out of that 4th gear snchro? Very easy shakedown driving no hard shifts etc....I have another bearing and synchro set coming but is there something wrong that caused this to happen? Its a close ratio stock original piece. At one time someone had rebuilt it, there was evidence of something coming apart inside. Your advice for things to check would be appreciated...I would like to keep the transmission in this car for longer than 25 miles...thats the streak I have going so far. Remember my ball stud length problem and clutch adjustment!
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Dino Lanno -
Re: C2-1964 Transmission 4 speed
Dinno-----
My guesses:
1) Some sort of assembly problem when the synchro assemblies were put together by yourself or whoever did it;
2) Defective or incorrect synchro rings. 1963-65 Muncie synchro rings are different than the 66-74 type. They both look very similar, though.In Appreciation of John Hinckley -
Re: C2-1964 Transmission 4 speed
Dino; When the trans is asssembled the out-put shaft with all gears and center sprt. are in place and this unit is placed down in the main case that allready has the cluster gear and 4th gear (in-put shaft) installed. At this point there are a number of things that can go wrong: 1) the 3 dogs which engage with the 4th gear brass ring (syncro) may not have been linned up with the slots in the ring causing a bind point. 2) the bearings that fit inside of the in-put shaft may have gotten themselves out of place (some people choose not to use the cage that keeps them in place) this will cause a bind point. 3) the space in between 4th gear and the syncro hub may be too wide or narrow (improper use of shims; to move 4th gear into trans) or (improper use of syncro hub/syncro ring combo) (wrong year parts together)or (parts not assembled onto out-put shaft properly)---wrong use of selective fit snap rings. 4)Front nut that holds main bearing to in-put shaft loose (allows in-put shaft to move in), I think #1 is the most probable cause though .DavidComment
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Re: C2-1964 Transmission 4 speed
David, Thank you very much for the response, it appears that the space in between 4th gear and the syncro hub was too narrow (improper use of shims; to move 4th gear into trans)The transmission never had shims in it, but it appears to be to close so I am assuming by adding the shims, the dogs will be kept form being chewed up....do you know why the trans didnt have them before and know requires them?Dino LannoComment
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Re: C2-1964 Transmission 4 speed
Dino,
I rebuild Muncies and I've seen this twice in the last 2 years. In my opinion the cause is too much space between the input shaft and the mainshaft. One is held in by the front of the maincase the other by the mid plate. When the maincase or the mid plate gets distorted the gap widens until the dogs spin out of their slots in the synchro. I personaly don't like shims but you can correct the problem by installing the thicker aftermarket oil slinger between the input and the bearing. This puts the input in further. Or you can replace the maincase and/or the midplate. If the bearing slides in and out of the mid plate and the outer race spins, definitely replace the mid plate. I have seen some mid plates where the bearings would slide freely 30-40 thousanths this is a bad situation. The rear bearing should fit snug in the midplate and not move easily. Unless you want originality there is a steel aftermarket mid plate I would recommend. Otherwise you are at the mercy of the Ebay junk pile. In the last tranny I experienced the problem, I used the slinger and replaced the midplate and the guy hasn't been back to see me.Comment
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Re: C2-1964 Transmission 4 speed
Dino; Larry is right on with the shims, most trannys never had any and they will move the in-put shaft toward the rear of the trans and close the gap, not make it more open. The mid plates can be damaged from snap ring groove wear to being hit in the rear end (drive shaft), improper instalation (bolting tranny together before parts mate),to just plain wore out. Some people leave out the gaskets in an effort to get the main shaft closer to the front of the tranny, they use sealant instead. The front bearing retainer can be worn in the area that holds the in-put bearing and the case can be in bad shape in many ways as Larry said.
In my experience the more new parts that go into a muncie, the better and longer they work. The assembly process can cause problems as I mentioned before so you need some-one who is good with these things to help you learn how to look for the pit falls. If the person is haveing trouble just putting it together then he probably is'nt looking for the problems that cause one to act strange when it is done. DavidComment
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