# wrong driveshaft! help...



## yousaygo (Apr 3, 2006)

Hi, My Muncie 4 speed started to make some noise is 2/3rd gear, put clutch in and it would stop. Thought it was throw out bearing, did not have time to do it myself so i dropped it off at a friends shop. He pulled tranny out and noticed shaft would make noise if spin manual, he said it was an internal bearing (I forget name, release bearing?).

Important: he noticed that this was caused by my driveshaft being too long and pushing on the inside of tranny (sorry if i do not describe that well). 
When i got the car, it was an automatic, i had the Muncie from a previous GTO, (not original tranny either), and made the car a 4 speed (of course). I remember that it did not seem perfect, especially finding right u-joints, but thought it was ok, now i have a big time issue preventing me from driving the GTO. It has a 12 bolt, and i am not sure if it is a M21 or M22, may not matter in this case anyway.

*Question: How do i determine the correct length of a new driveshaft?*

*Question: How do i even start figuring this out to find a driveshaft, and more u-joint searching.*

There must a trick to doing this, you experts must change tranny's all the time, how do you know how to match up a driveshaft to the tranny and rear end?

Thank you, we are mid-summer and i drive my car daily, even at 8mpg  
I appreciate your help as always, i am next to my computer out in the garage wondering what to do so i do not muck up my car any more and get driving it 
Peace, Shane


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## twomedicine1 (Feb 6, 2011)

*Driveshaft*

M 21 or 22 wont matter. I do have an extra original shaft for a 65 and I will measure it and get back to you..


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## freethinker (Nov 14, 2009)

yousaygo said:


> Hi, My Muncie 4 speed started to make some noise is 2/3rd gear, put clutch in and it would stop. Thought it was throw out bearing, did not have time to do it myself so i dropped it off at a friends shop. He pulled tranny out and noticed shaft would make noise if spin manual, he said it was an internal bearing (I forget name, release bearing?).
> 
> Important: he noticed that this was caused by my driveshaft being too long and pushing on the inside of tranny (sorry if i do not describe that well).
> When i got the car, it was an automatic, i had the Muncie from a previous GTO, (not original tranny either), and made the car a 4 speed (of course). I remember that it did not seem perfect, especially finding right u-joints, but thought it was ok, now i have a big time issue preventing me from driving the GTO. It has a 12 bolt, and i am not sure if it is a M21 or M22, may not matter in this case anyway.
> ...


auto and 4 speed should take the same shaft. reassemble it and take note of the yoke travel. make sure the yoke is not butting up against the output shaft. dont remember the exact amount of travel needed but about an inch should be enough.


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## ALKYGTO (Mar 29, 2010)

First, I absolutely love the look of your car. Completely Badass stance. And I really dig the color combo. It would look perfect sitting in my garage parked next to my 69.  I wish!

Driveshaft length should'nt have changed by changing from auto to man.

But since your car does sit so high, if you can see under it when it's sitting on a flat surface you should see about 1"-1 1/2" of your driveshaft yoke sticking out of the tranny. If it's bottomed out now or only has 1/2" or less it probably is bottoming out as the suspension travels.

Shortening is pretty easy, you just have to keep everything in line when you weld it back together so it does'nt lose it's balance and the yokes stay in phase so you don't get any harmonics.


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## freethinker (Nov 14, 2009)

yea. if it is too long shortening it is easy. just take it to a driveshaft shop and have them shorten it. the last one i did was only about $50 bucks.


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## yousaygo (Apr 3, 2006)

Awesome help, really appreciate it. The driveshaft info you provided is extremely helpful, i just do not have this great knowledge you share, THANKS. 

I seem to have a bad bearing in my tranny, i am debating whether to fix myself (never done one but probably possible) or i got a guy i can trade it in on for a used M21. The M21 is about $800, this seem reasonable?

Just wanted to update this with you.


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## freethinker (Nov 14, 2009)

yousaygo said:


> Awesome help, really appreciate it. The driveshaft info you provided is extremely helpful, i just do not have this great knowledge you share, THANKS.
> 
> I seem to have a bad bearing in my tranny, i am debating whether to fix myself (never done one but probably possible) or i got a guy i can trade it in on for a used M21. The M21 is about $800, this seem reasonable?
> 
> Just wanted to update this with you.


no. i would fix my own. you may be getting something just as bad as yours. they are not that hard to fix.


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## ALKYGTO (Mar 29, 2010)

:agree


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## geeteeohguy (Feb 2, 2008)

$800 will buy a good rebuilt Muncie....an M20 or M21. Not a screaming deal for a used one. The bearings go bad fairly easliy. I would recommend a master rebuild kit (about $250 for everything) and have someone who knows Muncie's go through it. They are not super difficult, but you need a press and a lot of patience. The kit will have new shift forks, a new countershaft, new synchros, new bearings, etc. Because of the labor, the best way to do it is to do it once and do it right. M-22's are more $$$. If you have a 3.90 or 4.11 rear gear, an M-21 is the way to go. If you have a more highway friendly gear, the M-20 has the M-21 beat hands down.


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## Eric Animal (Oct 28, 2007)

Try Medatronics Corporation's 5 Speed Home page!for a rebuild kit and tech assistance.......Eric:cheers


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## BearGFR (Aug 25, 2008)

yousaygo said:


> *Question: How do i determine the correct length of a new driveshaft?*


Hey Shane,

If all else fails you can have one made. That's what I did (had to because I put in a Ford 9" rear)

I got mine here: Spohn Performance Custom Driveshafts

There are instructions there about what/how to measure to make sure you get the correct length.

Bear


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