Muncie Strength?
 

I have a 73 Ventura Sprint (74 GTO clone) with a 455, stock 6x-8 heads, Comp "280" cam (230° duration at .050, .480 lift), Holley 750 on a stock intake, and long branch manifolds with 2.5" exhaust. It has a 4-speed and a 3.73 10 bolt. It runs 13 flat at 105 on street tires. I have broken two axle shafts on the 10 bolt, so I used part of my tax return and ordered a Moser 12-bolt (3.42 gears, True-trac posi, 33 spline axles). I plan to get some stickier tires, which leads me to my next weak link - the Muncie. It has held up admirably over the last 10 years of abuse, but that was with street tires (best 60-foot time of 1.87). Eventually I want a TKO, but for now I am thinking I might upgrade the Muncie to an aftermarket case, steel midplate and M22 gears. I already have an M22 input shaft, and 2nd and 3rd gears, and I can get the rest of the parts for around $700. Any thoughts on how much abuse this will take? Anyone else running a Muncie reliably?

I will be out abusing my new differential at the Pontiac Heaven event on April 5....

Thanks, Importsmasher

i'll go out on a limb and do some guessing...I don't own an automatic car :)
+/- 50 horsepower :)


400 - 450 horsepower = M20
450 - 475 HP = M21
500 or so horsepower = M22

I agree with the typical statement that it depends on the muncie. In particular, make sure the linkage is adjusted well

that autogear conversion supposedly pushes it up to 600 horsepower

I would sell it and save up some more money and go with something else, maybe a TKO 600 or a Jerico. You can get a Jerico DR-4 with road race sliders for under $2600 (last time I looked, about a year ago) and I doubt you would break that.

OK, I just checked and the Jerico is a little higher now......
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Drag Racing 4-Speed, Clutch-Type, Top- and Bottom-Loader (#DR4)
Caged needle bearings are now standard in the cluster. Jerico® is always improving. New alloys and evolutionary gear design changes continuously increases strength and decreases power loss. $2,750.00
Optional road race sliders are free....they will allow easier downshifts.
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I would imagine you would have a hard time breaking a Jerico.............personally, I would buy that before I would waste time and money to modify that Muncie. Just my opinion........

Importsmasher,

I just went down the same road last year. 570 HP/ 590 TQ at the engine, new Centerforce DF, new 12 bolt, 35 sline strange axles, Detroit locker, new driveshaft with 1350 u-joints, and new rear suspension. My weak link was my original M-20.

I left third gear on the road one sunday night taking my wife for a ride. I have since replaced it with a Auto Gear M-22 Super case combo. I have had no problems yet, but this year the car will have a set of new M/T slicks. I'm keeping my fingers crossed.

Don't find the weak point the hard way, keep upgrading.

Best of luck, sounds like a very cool ride.

It is not the HP that kills them it 550+tqe that will destroy them with traction.

If you can manage the tque properly they will prob live. If you look up Guidos on this site he went to a dual disc adj friction clutch which comes in "soft" then grips. NOT cheap.

TKO is good but not bulletproof either, if you're serious about running a clutch car investigate a Jerico---again not cheap.

I hope you're already running a block plate and scatter shield??

Thanks for the replies. Unfortunately, buying the 12 bolt to fix my first weak link sapped all my money, so a Jerico or TKO is not an option right now and I am not willing to run an automatic.

I will refrain from running too sticky of tires, and will (hopefully) soon upgrade my M20 to an M22 as I mentioned ($700 instead of $2700), and hope for the best....The M20 has held up so far, as I have been running this combination since 1998.

Ponjohn, I do have a scatter shield, Hays flywheel and CenterForce clutch.

Importsmasher

Just curious but has anyone found those Muncie replacement gears,parts etc that are American made?
All I ve found is India,Spain,Pakistan and of course China.

The gear sets that come in the supercase muncie are supposed to be made in Italy by a company that supplies the auto industry with OEM gearsets.
Importsmasher, if your going with 3.42 gears then I would go with the m22w gearset from Autogear in your muncie. The gears are cut straight like an m22 for strength but are a wide ratio like your m20. Close ratio gearsets are better with rear end ratios 3.90 and up and wide ratio 3.73 and down as a general rule.

ANDYA,
I will be going with the close ratio gears simply because that is what I have. I got the input, and 2nd and 3rd gears for free (new in the box), so I will be purchasing the compatible cluster. If I was buying everything from scratch, I would go with the wide ratio gears. For the rear end, I really wanted to go with a 3.23 ratio, but Moser doesn't offer it (the 10-bolt I am replacing is a 3.70). I know the factory used close ratio on 3.90 and up, but none of my cars seem to care. I have a close ratio in my 67 full size wagon with 3.23 gears (only because the $50 transmission I found was a close ratio), and I tow with it regularly. Also, I had close ratio gears in my 66 GTO convertible (3.55 rear), and when I had the transmission out recently, I put the correct wide ratio gearset in it, but I can't tell the difference. I don't remember if the transmission currently in my 74 GTO is close or wide ratio.
Importsmasher

Hey Importsmasher. If you aren't careful on what you build, your brothers 'cuda might be faster!!! HAHAHA!!

Aaron