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zz502 killed my M21 Munci

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Old 10-02-2013, 03:21 PM   #1
zuendler
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Default zz502 killed my M21 Muncie





Is this something I had to expect? I was shifting with 2/3 throttle, from 2nd to 3rd. I was a bit late on the clutch, means I pushed the stick a bit while clutch was not fully released. Then something broke inside...

What now? Engine has ~ 550ft/lb.
All normal Keisler tranys are rated to 500ft/lb,
except the TKO600 and SS700

Last edited by zuendler; 10-02-2013 at 06:07 PM.
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Old 10-02-2013, 03:28 PM   #2
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The M21 helical gears are designed to run quiet. Straight cut gears like the M22 are much stronger but whine. The M21 wasn't designed for performance 500" engines.
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Old 10-02-2013, 04:46 PM   #3
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I have to find out if the SS700 can be delivered without waiting 6 months now. And if it can be put in place without removing the cross member and to do it all in my garage, without a car lift.
Any experiences?

I thought also about just restoring the M21 - but I think thats no option, because it will break again.
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Old 10-02-2013, 04:50 PM   #4
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contact a company similar to this to upgrade the transmission

http://www.riversidegear.com/muncie-4-speed/
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Old 10-02-2013, 05:00 PM   #5
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If you stay with a Muncie, Autogear offers a lot of upgrades.
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Old 10-02-2013, 05:19 PM   #6
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wow, Keisler is responding within seconds! They cant give any delivery date for new orders on the SS700. So this option is out.
I wonīt stay with the Muncie, because I want an overdrive gear.
So only the TKO 600 is left.
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Old 10-02-2013, 06:07 PM   #7
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I am easy on my clutch, but take my 550 ft-lb 468 to 6500 and shift quick. TKO600 has been fine with that. My Vette-brother runs 501 RWT with TKO600 and no problems for 2 years. like me, he is also not a clutch-popper.
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Old 10-02-2013, 06:11 PM   #8
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Quote:
Originally Posted by zuendler View Post
wow, Keisler is responding within seconds! They cant give any delivery date for new orders on the SS700. So this option is out.
I wonīt stay with the Muncie, because I want an overdrive gear.
So only the TKO 600 is left.
Give the folks at hurst driveline a call for a TKO600.
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Old 10-02-2013, 06:18 PM   #9
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RayY on CF runs a 555ci engine with 3.73 and TKO600. I believe he has had that combination for a year or 2. Just recently, he confirmed that it was working fine on a thread here.

I am a few weeks away from running a 540 through my TKO600. With my driving style, I think it will be fine. Obviously, that's not evidence.
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Old 10-02-2013, 07:02 PM   #10
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M21 + 3.08 rear end + 285/40/18 Toyos + 565 ft/lbs - 4 years in the car and Muncie is holding-up fine so far (unlike stock engine mounts)
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Old 10-02-2013, 07:18 PM   #11
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Quote:
Originally Posted by v2racing View Post
The M21 helical gears are designed to run quiet. Straight cut gears like the M22 are much stronger but whine. The M21 wasn't designed for performance 500" engines.
M-20/21 gears are cut at a 45 degree angle, the M-22 gearset is 22.5 degrees, I find the sound of an M-22 less offensive than a ZF 6 speed in a C4 Corvette myself. Autogear has M-22 style gears in both traditional "close ratio M-21" and "wide ratio M-20" gear ratios, either set would handle that power, you should also investigate using the Autogear "super case" reinforced Muncie main case and iron mid plate.
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Old 10-02-2013, 07:53 PM   #12
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Trans had it comin'
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Old 10-02-2013, 08:55 PM   #13
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Autogear also has a gearset that makes 4th an OD.

http://www.autogear.net/pdf/HighPer_..._sheet_t10.pdf
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Old 10-02-2013, 09:30 PM   #14
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Default Zz502 killed my Muncie

I have a rebuilt Muncie with a gear vendors overdrive behind my 496 full roller that dynoed at 635 hp . Very solid very strong and overdrive in any gear plus one clutch-less shift. Rebuilt Muncie $500 GVO $3,000 installation $ 1,500 ? Not too bad. Check out GVO they are even warranted for drag racing.

My $.02
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Old 10-03-2013, 01:24 PM   #15
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T-56 Magnum behind my 496 BBC. 700 ft lb rating, 5th and 6th overdrive.

Quicktime has a conversion bellhousing for the LS spec transmission behind a traditional Chevy engine. Hurst Driveline had a modified QT bellhousing and the parts (throwout bearing sleeve) to allow a mechanical clutch linkage. Had to modify the crossmember (used a BowTie Overdrives T56 unit with slight mods), 1310 billet yoke with removable caps, and custom driveshaft. Used a 73-81 T56 Camaro shifter, rotated the stick part 180 degrees and it fit the stock console perfectly (already had a large center hole from earlier Tremec 3550 swap).

I have the version with 2.66 first and .8/.62 overdrive. Works great with my 3.73 12 bolt rear.

More info on the Hurst parts here:
http://www.chevelles.com/forums/showthread.php?t=325170

Last edited by SteveG75; 10-03-2013 at 01:29 PM.
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Old 10-03-2013, 02:58 PM   #16
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Shockloads will kill any trans sooner or later.
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Old 10-04-2013, 01:16 PM   #17
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Owning a TKO600, if I could do it all over again I'd go with a T56.
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Old 10-04-2013, 01:55 PM   #18
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I have the TKO600 behind a 468 with a 3.55 rear end and 27in tire height. It will lug along at 1400-1500 rpms and 50mph and is extremely happy in the 1900-2100, 65-70 mph range. I can see where some would want an OD gear that is more in the .75 ratio bur for a driver like mine is the .64 is great.
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Old 10-04-2013, 05:02 PM   #19
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Quote:
Originally Posted by Shark Racer View Post
Owning a TKO600, if I could do it all over again I'd go with a T56.
Why the T56? 6th gear? Torque capacity? What is the torque capacity?

Didn't consider it because I didn't like the idea of messing with the fiberglass and console or the welded up offset shifter. So I bought the TKO. And then immediately got the sawzall out and cut up my crossmember. LOL.
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Old 10-05-2013, 12:00 AM   #20
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Quote:
Originally Posted by Super6 View Post
Why the T56? 6th gear? Torque capacity? What is the torque capacity?

Didn't consider it because I didn't like the idea of messing with the fiberglass and console or the welded up offset shifter. So I bought the TKO. And then immediately got the sawzall out and cut up my crossmember. LOL.
I have a 78 which originally came with an auto, so I had to cut the floorboard regardless. I ran a hydraulic clutch release assembly. Soooo, I pretty much did everything I would have had to to do install a T56.

That said, the T56 shifts better, does have the extra gear and would have come in at the same price or possibly lower. Speedometer output would have been an issue, but not unsolvable.

The lower geared T56 (like in a GTO) would have probably been the better choice for my personal setup. As for torque capacity, 400lb-ft +, depends on the source application. A T56 magnum comes in at 700LB-FT.
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