Hi Guys and gals,

I had a similar problem years ago.  The forks were worn to where they would not push the syncro's far enough.  Two new forks and it worked fine.


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The broken keys are more likely from the 1-2 synchro assembly, since you have to sometimes man-handle it into 1st, and it falls out of 2nd on deceleration. The grind on the 3-2 shift is most likely just normal wear/tear on the brass rings. There is probably some wear on both forks, for sure.....there almost always is. Regardless, the trans will need to be removed and repaired. While it's out, might as well go ahead and do a complete rebuild, with new bearings/brass/seals, plus whatever worn/damaged parts that need replacing.
I wouldn't recommend doing much more driving with known broken synchro keys....you could do a lot of damage if even a small piece of one gets in between two gearsets....ouch! Those keys also help keep the brass(synchro rings) from spinning on the hubs/gears. If the brass starts spinning like that, it can damage the hubs....more $$$$, not to mention the grinds while shifting will wear the synchro teeth off of the speed gears rather quickly.

|UPDATED|9/14/2016 9:43:26 AM (AZT)|/UPDATED|


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Joel Adams
C3VR Lifetime Member #56    
My Link


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"Money can't buy happiness -- but somehow it's more comforting to cry in a CORVETTE than in a Kia"

Hi Joel, I don't quite have to manhandle it into 1st just a little extra pressure and it goes in, I suspect this is more likely to be selector fork worn which would also explain the jumping out of 2nd, something I experienced many years ago on a Ford, it was only when i got the new forks I realised how badly worn they were( I thought they were machined that way!)
It's 2-3 or 4-3 where I get the crunch which leads me to suspect that's where the broken keys came from, obviously when it's out I'll do a full overhaul replacing any worn or broken parts, new bearings and seals, etc.not a job I'm particularly looking forward to but certainly not a job i want to do more than once
More importantly I'm looking for a source of good quality parts at fair prices, any suggestions anyone?

Thanks
Graham

Does nobody do their own repairs any more? unfortunately I don't have the luxury of exchange reconditioned units in the UK so I have to do it myself, I've done gearboxes myself in the past so not phased at all but would like some help as to where to obtain good quality parts as once it goes back in the car I don't want to be pulling it out again a few months down the road.

I bought my rebuild kit for my Muncie 20 from Paul Cangialosi at Medatronics Corp in Tequesta, Fl.  Phone # (561) 743-5600.  I rebuild the Muncie myself - my first attempt and it isn't that difficult.  I bought Paul's book on Muncie 4-speeds - How to rebuild and modify and just followed his very detailed instructions.  His web site is www.5speeds.com  He also rebuilds Muncie's.

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Hi Bob, thanks for the recommend I'll have a look at their site.
Regards
Graham

I do mine, Graham. I also build transmissions for a living. I haven't given any suggestions on where to get parts because of your location. I've shipped trans parts over to that side of the pond for another C3VR member....and it turned into a big "hurry up and wait" situation with customs.
The best place(imho) in the states to get whatever you need for it is Kajun Jon's . Don't know if he ships overseas or not, but you can certainly contact him once you find out what all you need. 


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Joel Adams
C3VR Lifetime Member #56    
My Link


(click for Texas-sized view!)             NCRS

"Money can't buy happiness -- but somehow it's more comforting to cry in a CORVETTE than in a Kia"

That would be my recommendation as well, if you go to web site or you tube you will find some good videos. Muncie's aren't too bad to work on but the gears are made outside of the USA now.

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Thanks guys, that's the kind of info i nee, I understand the problems of getting parts delivered and the often high additional costs of shipping and duty.
I've managed to make contact with the Italian manufacturer, Antonio Masiero, that a lot of the US parts suppliers are using and come highly recommended with users and am hoping they can supply via a European agent if not direct, they initially pointed me to Autogear in the US as their exclusive agents.
Thanks
Graham

I've been reading up on the subject and now have a better appreciation of what I am going to be up against but as a marine engineer of many years experience nothing to phaze me.
I bought a copy of Paul Cangialosi's excellent book which has been very informative.
As I will be going from a 4.55 to a 3.55 diff at the same time I'm going for a slight change of ratios in the box so the input shaft and countershaft gears will be new anyway, I now have a better idea of what is worn out unlike when I did my first gearbox as a youngster!!
I'll keep in touch as I progress.
Graham

You're going for the overdrive conversion, aren't you?!
Done a few for others....it's a good compromise to going to a 5 speed...and still looks original.



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Joel Adams
C3VR Lifetime Member #56    
My Link


(click for Texas-sized view!)             NCRS

"Money can't buy happiness -- but somehow it's more comforting to cry in a CORVETTE than in a Kia"

Hi Joel, not so much an overdrive but i'm changing my diff from a 4.55 to a 3.55 so thought my 2.2 1st gear would be a bit tall so I think I'll go with Autogears M22w set up which gives 2.56/1.75/1.36/1.00 ratios.
I've seen the o/d gears offered but a bit puzzled as to how it's achieved as top is normally straight through 1:1?
I had considered going for a 5 speed but with shipping and customs it's just a bit too much.
Graham

Graham, the O/D set-up for the Muncies is a neat deal. It actually changes 3rd gear to an overdrive ratio, leaving 4th gear as is. You flip the lever on the side cover for the 3-4 shaft over, and it now goes from 1st, to 2nd normally, and when you shift into what was 3rd, it actually shifts the trans to 4th(direct), then the shift into what was 4th is now an overdrive ratio replacing 3rd. The kit changes the cluster gear, along with the 2nd and 3rd(O/D) gears on the mainshaft. The 2nd gear change is so there isn't such a large gap between the 2nd and 4th(now technically) 3rd gear ratios.  

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Joel Adams
C3VR Lifetime Member #56    
My Link


(click for Texas-sized view!)             NCRS

"Money can't buy happiness -- but somehow it's more comforting to cry in a CORVETTE than in a Kia"

I did wonder if that's how it's done a bit like a 3 speed and overdrive then. Graham

Took the box out last night and not a pretty sight, only half a key left in the 3/4 synchro hub so no wonder it had a bit of a crunch! the 1/2 hub is very loose and sloppy and the engagement teeth are a bit rounded so even if I wasn't changing the ratios they'd need replacement anyway, will hopefully get it all in bits tonight and see what the reverse gear is like then should be ready to order the parts, side cover looks good just needs new seals, I haven't measured the forks yet but they don't look too bad, although I already have a new set.

I was looking at my shifter yesterday and with a bit of fettling I think it should be salvageable, I think there should be a bias spring to push the lever over towards the 3/4 gate? which is missing had a look at the assembly manual and couldn't find a drawing there, am I right?Graham 

Got my new clutch so that will go on first, when I removed the old one I found a needle roller spigot bearing, should I keep this or change it for the bronze bush supplied in the clutch kit?
Should get my gearbox parts in about a weeks time so will probably pulll my diff while I'm waiting.
Graham

As the needle roller spigot bearing was in good condition I left it in place only cleaned it and gave it a lick of fresh grease, so new clutch mounted, gave the aluminium housing a good clean and a fresh coat of orange engine paint while it was off, new rubber boot fitted around the clutch arm as the old one fell to bits so will put that back on next then should be getting my gearbox parts through in the next couple of days so can get on with putting it all back together.

Started building up the gearbox yesterday, all gears back in the box, just got to helicoil one of the mounting bolt holes on the tail housing before I put that back on and it's all ready to go back in.

Managed to find the correct position for the speedo gear by fitting the old one and measuring the position it was a bit tricky and involved some maths as the new one was slightly thinner.

Got my box back together OK, refitted the original speedo gear and took measurements then mounted the new one in the same position and when the tailhousing went back on it all lined up, box back in the car now so on to the next job, change diff gears from 4.56 to 3.55 to give better highway cruising revs.

Graham

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Cheers Gary, yes all sorted got a new diff with new crown wheel and pinion set, went for an Auburn unit and Nitro gears so hopefully it all goes together OK, not looking forward to shimming the pinion shaft, any suggestion for a starting point for the shim size? I don't want to have to pull the bearing off more than necessary.

|UPDATED|12/2/2016 3:28:45 AM (AZT)|/UPDATED|

An Auburn is a cone type posi, ok but not as strong as an Eaton. They do cost less and are not rebuildable. If you are building the diff for under 400hp and just street driving it should be ok. If more hp and hard use I would reconsider using the Auburn.

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Hi Gary If I can get to the original 350HP I'll be happy so the Auburn should see me out.
These are the diff gears http://www.nitro-gear.com/GMVET-355-NG-p/gmvet-355-ng.htm they come with a 2 year warrantee so they should be OK I'm only a weekend cruiser so if they're as good as they make out on their website I'll be good.
What do you suggest for a starting shim for the pinion shaft Gary?

Many Thanks
Graham

I am going to take a guess here and say those are reboxed Tom's gears. Did you get them in yet?

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Hi Gary, yes I got them earlier in the year ready for the winter, I'll have another look I know there are some etched markings so they're a matched set will have another look later.
Graham

Got my diff. all stripped at the weekend bar the pinion shaft which my friend pressed out for me this morning, good to have friends with a 60 ton press!

Hi Gary, apparently the Auburn diff is rebuildable, I was reading the bumf that came with it and apparently they do a rebuild kit which has all the internals, new cones, gears, etc. but as I say I hope it will last for a good while!

Graham

Interesting on the rebuild kit, I hope you don't need it.

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Finally it stopped raining and I could get  out for a little run for Drive It Day, all good, the taller diff ratio has made a big difference, pleased I changed the first gear ratio as I think the original might have been a bit too tall.
Speedo seems to be about right, haven't checked it against sat nav yet but revs seem about right for the indicated speed.
The composite spring I fitted during the job is a big improvement on the steel original and at last the car sits level, I haven't a clue what poundage it is but ride is much better, also the adjustable strut rods made setting up the camber a piece of cake.
Thanks
Graham

Update after a year of running, change of diff ratio was well worth it, makes cruising much more relaxed, had a bit of a whine but this has quietened down with a bit of running so guess it is running in nicely.
Only problem I have now is with the clutch adjustment, I fitted a new LUK clutch kit complete as the upgraded input shaft had different splines, I fitted the new release bearing supplied with the kit but retained the original ball stud and release fork.
Problem I now have is that in order to get the clutch to disengage I had to wind the adjustment all the way to the end of the thread so I don't even have room for the second lock nut! I didn't remove the ball stud so I don't know what length it is but can see there are various lengths ranging from 1 3/8" to 1 13/16" so perhaps I need a longer one but whatever it is the gearbox will need to come out again :-(
Graham