Glad I checked.
Is M20 Damage Possible?
Thread Starter
Melting Slicks
Joined: Oct 2013
Posts: 2,569
Likes: 126
From: San Diego California
Is M20 Damage Possible?
Having just installed a newly rebuilt pre-68 M20 in my '73, I want to know from the experts here about this subject.
Is it possible to cause premature wear in the transmission with mal-adjusted shift rods, within say a 200-300 mile driving distance?
In test driving it around town, Neutral is easily moved fully from side to side, shifts in all gears fairly well, and stays in the selected gear without popping out. I say "fairly well" because it being freshly rebuilt with all new internal parts (according to the seller), perhaps that's why it's not "butter-smooth". But what do I know? Are these transmissions so fine, that if a shift rod is pushing/pulling a transmission lever into a not-quite-perfect position, internal transmission parts can be damaged quickly?
I'd like to think these Muncie Transmissions are relatively bullet proof, but being new to it, I need some knowledgeable feedback on this.
I'm actually having trouble finding a reputable transmission shop who will schedule a check of this for me, and not have to leave the car there a day or two for them to do it. You would think there would be one in a city this size, but no luck so far.
Thanks for your thoughts on this. I DON'T want to damage a new transmission.
Steve
Is it possible to cause premature wear in the transmission with mal-adjusted shift rods, within say a 200-300 mile driving distance?
In test driving it around town, Neutral is easily moved fully from side to side, shifts in all gears fairly well, and stays in the selected gear without popping out. I say "fairly well" because it being freshly rebuilt with all new internal parts (according to the seller), perhaps that's why it's not "butter-smooth". But what do I know? Are these transmissions so fine, that if a shift rod is pushing/pulling a transmission lever into a not-quite-perfect position, internal transmission parts can be damaged quickly?
I'd like to think these Muncie Transmissions are relatively bullet proof, but being new to it, I need some knowledgeable feedback on this.
I'm actually having trouble finding a reputable transmission shop who will schedule a check of this for me, and not have to leave the car there a day or two for them to do it. You would think there would be one in a city this size, but no luck so far.
Thanks for your thoughts on this. I DON'T want to damage a new transmission.
Steve
Thread Starter
Melting Slicks
Joined: Oct 2013
Posts: 2,569
Likes: 126
From: San Diego California
Good reminder about oil level. Was received "dry" and I filled it just before I put it in the car, but haven't checked it since the test drive.
Steve
Old Pro Solo Guy
Joined: Dec 2017
Posts: 8,014
Likes: 4,369
From: Marlton NJ
I think with what you said a few hundred miles should not have hurt it.
"Hurt" symptoms include:
Just don't give it full throttle if you think it might only be half way into gear, or it's slipping out, you can chip a tooth that way.
They are not bulletproof by any means but a good build should be able to handle 400+HP for a long time, shifted sanely.
So based on what you wrote, why do you think the rods are mis-adjusted anyway?
The real test is a smooth 2-3 shift, same for 1-4, and a smooth 3-2 downshift.
It usually needs to be zig-zagged a little, but if you have to completely stop making forward progress to 3rd, and jiggle it, that's not good.
"Hurt" symptoms include:
- popping out of gear because you have a lot of wear on a tooth
- grinding going into gear b/c you messed up a synchronizer
- Awful whirring noises because you hurt a dry bearing
- Awful grinding or clunking noises b/c you broke off part of a tooth that was half engaged
- It's normal for them to be a little notchy due to new synchros, but balking to go in gear either means hurt, or mis-adjusted
Just don't give it full throttle if you think it might only be half way into gear, or it's slipping out, you can chip a tooth that way.
They are not bulletproof by any means but a good build should be able to handle 400+HP for a long time, shifted sanely.
So based on what you wrote, why do you think the rods are mis-adjusted anyway?
The real test is a smooth 2-3 shift, same for 1-4, and a smooth 3-2 downshift.
It usually needs to be zig-zagged a little, but if you have to completely stop making forward progress to 3rd, and jiggle it, that's not good.
Thread Starter
Melting Slicks
Joined: Oct 2013
Posts: 2,569
Likes: 126
From: San Diego California
Thanks Leigh.
About to drop on the ole garage floor and see what the oil level is.
Would a slight pull out on the shifter ball from an engaged gear while driving and no clutch engagement, to see if it pops easily out of gear, help verify improper Rod Length adjustment?
Thanks again.
Steve
About to drop on the ole garage floor and see what the oil level is.
Would a slight pull out on the shifter ball from an engaged gear while driving and no clutch engagement, to see if it pops easily out of gear, help verify improper Rod Length adjustment?
Thanks again.
Steve
Thread Starter
Melting Slicks
Joined: Oct 2013
Posts: 2,569
Likes: 126
From: San Diego California
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Le Mans Master
Joined: Jun 2019
Posts: 7,642
Likes: 2,463
From: Indiana
Probably no issue slight overfill.
do youhave fill anddrain plugs? Or just a fill and you have to suck it out?
some have magnets on plugs. I liked to drain mine and check plugs after i rebuilt it.
if bored…not same bit similiar…especially the linkage adjustment learnings and fluid that helped me near end of thread below
Postsome pics of your tranny!
https://www.corvetteforum.com/forums...r-etc-diy.html
do youhave fill anddrain plugs? Or just a fill and you have to suck it out?
some have magnets on plugs. I liked to drain mine and check plugs after i rebuilt it.
if bored…not same bit similiar…especially the linkage adjustment learnings and fluid that helped me near end of thread below
Postsome pics of your tranny!
https://www.corvetteforum.com/forums...r-etc-diy.html
Thread Starter
Melting Slicks
Joined: Oct 2013
Posts: 2,569
Likes: 126
From: San Diego California
Race Director
Joined: Jul 2015
Posts: 13,082
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From: SW Florida.
if you can get to the shift forks, remove the shift rods. put trans in each gear. put shifter in same gear and see if shift rod will go into the lever without pulling the lever back toward neutral. if so for all 4 gears you are ok. the hurst has adjustable stops to avoid jamming it too far when shifting hard. don't think the oem shifter does. there are no partially engaged teeth. except possibly reverse. the rest of the gears are always fully engaged and the synchros lock each gear to the output shaft in turn. and 4th just locks input to output.
Le Mans Master
Joined: Mar 2001
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From: Lincoln, CA
My Autogear Muncie was not smooth either at 1st. I left the Sta-Lube gear oil in it for a while because that is what they suggested. After watching Paul the Muncie guys videos on gear oil I switch to Driven Oil. It's much smoother now.
Is my vette stock?? HAHA
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adjusted correctly and the proper oil , no you arent going to hurt it. With these shifters if it isnt going all the way into gear because of a poorly adjusted rod, then it would most likely pop out. You can check your shifters easily enough by removing the rod from the arm and shifting it into gear wih a adjustable wrench on the lever. then draw a mark from the arm to the case and then put it back in neutral. Reinstall the arm and shift it back into gear and see if the painted line lines up. If it doenst then lengthen the throw a bit and try again....
Thread Starter
Melting Slicks
Joined: Oct 2013
Posts: 2,569
Likes: 126
From: San Diego California
Thread Starter
Melting Slicks
Joined: Oct 2013
Posts: 2,569
Likes: 126
From: San Diego California
adjusted correctly and the proper oil , no you arent going to hurt it. With these shifters if it isnt going all the way into gear because of a poorly adjusted rod, then it would most likely pop out. You can check your shifters easily enough by removing the rod from the arm and shifting it into gear wih a adjustable wrench on the lever. then draw a mark from the arm to the case and then put it back in neutral. Reinstall the arm and shift it back into gear and see if the painted line lines up. If it doesn't then lengthen the throw a bit and try again....
With these great ideas from you guys, makes me feel I can forego the Tranny Shop *****.
Steve
Is my vette stock?? HAHA
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The oil looks fine. Just dont use a synthetic. It wont stick to the gears long enough to get it to the top. If you have a lot of questions look up Paul Cangliosi. He has a lot of videos on youtube and owns 5speeds.com
Is my vette stock?? HAHA
Joined: Oct 2015
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Likes: 9,237
From: Im not allowed to tell you
2020 C3 of the Year Finalist - Modified
2020 Corvette of the Year Finalist (performance mods)
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You should be good on the shift rod length then. If it feels grabby or wont go into gear easily then you may need to adjust it for neutral using the thin alignment tool
Thread Starter
Melting Slicks
Joined: Oct 2013
Posts: 2,569
Likes: 126
From: San Diego California
Is my vette stock?? HAHA
Joined: Oct 2015
Posts: 20,108
Likes: 9,237
From: Im not allowed to tell you
2020 C3 of the Year Finalist - Modified
2020 Corvette of the Year Finalist (performance mods)
2019 C3 of Year Winner (performance mods)
2016 C3 of Year Finalist