Diagnostic Help with Muncie
 

Now that a large contingent of the CF C1/C2 Brain Trust is here, I figured I should take advantage of the expertise you guys and those of you who are already residents here have.

I've had a problem with my '67's transmission (out of a '66 car, I think) for a couple of years now.

There's a gear clash from 3rd to 4th. I followed Frankie's advice when the problem first showed up a couple of years ago by replacing whatever fluid was in the trans with Brad Penn GL-4 80W-90. That helped for awhile but the problem eventually returned.

My work around has been:

1. Double-clutch - no clash at all
2. Pull out of 3rd, wait a moment, ease into 4th - very minor clash

My car's still in the shop after my ride of shame last week and I'm in no huge rush to fix the problem (especially, if it's going to be expensive). I'll just continue with 1 and 2 above for awhile longer. But I'd really like to hear what you experts think the problem might be.

Thanks for the help, guys!
Steve

Without personal hands on experience with your Muncie, the VERY FIRST thing that comes to mind is worn brass syncro rings.
It is necessary to pull it apart to replace them, SO, if it were mine ----------------------------- if that was all that was needed, I'd replace all 4 syncro rings.
Yes, a rebuild with a rebuild kit would certainly be good ------------------- but may not be necessary.

Pull it out, bring it to me and I'll check it out.

Tom Parsons

Tom - You're lightning fast on the reply! Thanks. I was hoping you'd respond.

What you say makes sense. I'm going to have to nurse it along for awhile longer. If it has to come apart, I might as well go full in with replacing all questionable parts.

Or maybe it's time for a 5-speed. Have to think about that.

Thanks again,
Steve

I'm in a somewhat similar situation, Steve. The non-original T10 in my '63 is in need of some attention, but not urgently. There are two issues. One is a leaking tailshaft seal, which is almost surely a result of the moderate amount of axial lash I'm seeing that indicates wear on the bushing. The slip yoke might also have some wear. I haven't removed the yoke yet to inspect. The other issue is what I'm presuming to be a worn synchronizer on second gear. If I shift it quickly, it'll sometimes bite a bit, and it also often will pop out of second when decelerating in second gear. Third gear occasionally bites a tiny bit as well.

For now, I'm thinking I might drop by a local old-school transmission shop to see if the guy there would be able to pull the tailshaft bushing and drive in a new one and a new seal, with the gearbox in-car. I'm aware that there's a tool (Kent Moore, or Snap-On, IIRC) that can be used to extract the bushing. I'm really not eager to get into R&R of the transmission at this time. I can live with the worn synchros for a while, but I really hate fluid leaks.

Whenever the gearbox does come out, I'll be facing the decision of whether to rebuild the T10, install a Muncie instead, or go all-in on a five-speed conversion. I haven't heard much feedback on the TKX conversions yet, but that might turn out to be an appealing path forward.

I don't beat on the car, but the T10 is comparatively weak. If it needs more internally than synchros, I'd probably lean strongly toward the Muncie or five-speed option. IIRC, the date codes on this T10 indicate that it's out of a 1961 car.

Live well,

SJW

For those who are not intimately familiar with the M22 (which eventually got nicknamed "Rockcrusher"), it was simply a heavy duty Muncie, and because of the different angle of the gear teeth, it had a distinctive whine. Us gear head guys like and identify with that whine. MANY owners DID NOT LIKE that noisy whine. Also, originally, the M22 was ONLY a close ratio (2.20 1st gear) which was not very compatible with rearend ratios such as 3.08, 3.36.
Well, today there are several AFTERMARKET gear set ratios for the Muncie. One of the gear sets is an M22W (wide ratio). I have converted 2 M20s to M22W. One of them is in my 70 Chevelle. I LOVE THAT M22 WHINE!!!
SOOOOOOOOOOO, if a conversion is your future, and if for no other reason, you want to have "bragging rights", an M22W might be something to consider.
I did have a 3.07 12bolt posi in the Chevelle, but I have recently installed a 2.73 12bolt posi, and the M22W does just fine with that rear ratio. NO, it is NOT a rocket from a stop, but once rolling 5-10mph, it winds to the moon in 1st and 2nd gears. When getting on the Interstate at an entrance ramp, I am just at the shift point from 1st to 2nd, then it's gone!
My plan for the next M22W is to convert the M20 in the 56.

In my book, an M22W has 3 benefits. It works good with hiway rear gears, it's inherently stronger than a regular M20/M21----------------and best of all, it has that sweet M22 whine!

Tom,

If I were to swap in a Muncie that needed much internal work before it'd be ready to install, I'd definitely be looking hard at the M22W conversion, and for most of the reasons you cited.

The added strength of the M22 gears, and the whine, are both winning attributes for me.

My '63 has a 3.70 R&P in it presently, and there's nothing wrong with the diff at this time as far as I'm aware, so as much as I'd like to knock the revs down on the highway, a rear gear swap would not be in my near-term future. The T10 that's in the car has WR gears, and I have no interest in a CR four-speed for this car. The throttle response is sweet as it's presently configured, and a CR would noticeably dampen that.

Is the first gear ratio 2.54 with the M22W gear sets?

Live well,

SJW

I'm rethinking the idea of swapping in a 5-speed.

I don't do a lot of long distance driving and I'm not annoyed by side pipe drone, especially with the top up and A/C on. I can hear music and carry on a conversation without a lot of effort.

According to the numbers on on the case, my differential gearing is 3.70. However, the gears were changed somewhere along the line because it actually computes out to 3.55.

I've always wondered why a previous owner put in a transmission from a '66 and changed the rear end gearing. The car was pretty pristine when I bought it. No signs it was abused or modified or damaged in any way. Everything stock except the transmission and rear end (motor is original). PS and PB were aftermarket.

Take care,
Steve

Steve,

These old cars have been used, in many cases abused, worn out, rebuilt, and somehow survived to this day. I can speak from plenty of personal experience, that back in the day, it was more common for most of the guys I hung around to swap out components than it was to rebuild them. This was especially true for transmissions and diffs, and not much less true for engines. Back then, good used replacement gearboxes, diffs and engines were abundant and much cheaper than rebuilding. Especially for those of us who were getting by on not much $$$, it was just the quick, easy and cheap solution when we blew something up or it just plain wore out.

So many cars landed in boneyards with functioning components on them, the economics of the choices were much different than they are today. As just one example, I helped a buddy and a few other guys migrate the entire drivetrain from a '70 Monte Carlo that had a cracked frame, into another '70 Monte that had a tired drivetrain. We did the entire thing in an afternoon in his dad's backyard. No way that could happen if rebuilding was the path taken. We swapped out dozens of engines, transmissions, and third members back then. Never rebuilt any of them. It was just yank, replace, and go.

Also, back then nobody gave a rat's ass about serial numbers, part numbers, casting numbers and date codes. If it would bolt up and work, we did it and moved on with life. In some cases, we swapped for more performance, but in so many cases it was just to get back on the road ASAP. Fix it on Saturday or Sunday so that you could drive it to work on Monday.

Are you sure your R&P are 3.55? How'd you determine this? That's a very slight difference from 3.70, so it's easy to mistake one for the other, especially if trying to do so based on highway RPM in fourth gear. Loaded tire diameters can skew what you think are good numbers.

Live well,

SJW

Hey Steve - Yes, I remember the good old days back in the 60's. I didn't have the cash to do a lot of parts swapping back then but I remember my friends making treks to the junk yards to pull parts. The girl who lived across the street from me in grade school and high school ended up owning a major auto parts yard with her husband just down US 1 from me in Fredericksburg, VA after she graduated from high school.

We'll never see those days again.

As far as my rear end gear ratio, I agree. It could be 3.70. I did the calculation because my mechanic at the time who was a C2 restorer thought it was either 3.55 or 3.36 just based on how it felt when driving the car.

Here are the numbers I plugged into the online calculator:

RPM: 2,200
Tire diameter: 26.85"
MPH: 50 (clocked with an iPhone app, not the car's speedometer)

The result was 3.52

Of course, the wild card is the 2,200 rpm's. That could easily be off.

I also did the rear wheel and driveshaft rotation check and got similar results but, as you say, 3.70 is so close to 3.55 a visual check like that is pretty worthless.

Take care,
Steve

Steve,

I didn't have the cash back then to NOT swap in used engines, transmissions and third members! I couldn't afford any other option. :D

You're correct to point out that accuracy of the tach and speedo can also confound attempts to discern the difference between a 3.55 and 3.70 R&P. Bear in mind also that a tire's loaded O.D. will differ somewhat from its unloaded O.D. Put all of these uncertainties together, and it'll be pretty much guesswork to try to determine the ratio from the driver's seat. You'll do much better under the car, but even then, as you noted, the difference is slight, so still not all that easy to determine with certainty, but it can be done. It could be argued that the difference is so slight that maybe it doesn't matter for most purposes. Curiosity gets the better of us sometimes, but if somebody sneaked into your garage one night, and swapped your R&P from 3.55 to 3.70 or vice-versa, you'd probably never notice from the driver's seat.

Live well,

SJW

Steve - I’m okay with my differential but if you want sneak into my garage and swap out my transmission, I’ll make sure the dog is locked up.

Take care,
Steve

I've seen Ratdog's car more than once, she's a beauty and over 60 years lots of stuff can happen, a tranmission swap to a 66 Muncie could have been done because the original was screwing up and that's what some tech had laying around - they were just old Chevy's back then. I would say, yeah the synchros are going and there is not much to be done short of an overhaul as Tom has noted.... Not sure I trust Corvette Masters to do such work anymore. You could call Wes Pullin in Winter Garden: https://wespullin.com/

My '67 Chevelle SS-396 had the Muncie go out literally a few days befoe the new buyer was to pick it up. Wes "knew a guy" that rebuilds them and it operated so nicely after the overhaul I almost reconsidered selling it. Maybe he'll share the guy's info. Otherwise you can call Tony Coshignano at 407 249-3705 (home) ot 407 468-9657 (mobile) and get his opinion. Tony is a Corvette zealot and prob would rush over just to look at your car, he's also a first class mechanic on many aspects. He just helped a friend rebuild his rear suspension. Knowing you both a bit I'm betting Tony would be your new best friend.

Personally, I don't think a 5-speed swap in whould have much of an ROI, I did one on my 61 but I was driving highways EVERYwhere back then - a 3 hour run down the interstate to do a car show in Sarasota was a pretty normal thing for me a few years back.

As to SJW's remarks about swapping components about back in the day...there were plenty of donor cars that had good working parts:

Thanks, Frank. I put that information in my contacts file.

Since Bruce has a “Holley guy” to work on my car, I’m also going to ask him if he has a Muncie guy”. I’ve seen Bruce pull transmissions and install them but I don’t know if he works on them himself.

That’s a pretty cool, and sad, photo of that Corvette graveyard. The ‘57 Chevy sticks out like a sore thumb.

Take care,
Steve

Late to the party here, guys. What Tom and Franki said, of course. My take: 5 speeds are nice but, as Frank said, the ROI would not be realistic. Do it because you want to. I like the old 4 speeds, and old Hurst shifters. That's just me. With the right first gear in your 4 speed, like a 2.56-2.66-2.88, etc. you can run a 3.08 or lower rear and be fine in town and on the open road. My '61 runs a 3.36 Posi out back but a Super T-10 with a 3.42 first gear and 2.20 second gear. If GM made a 2.73 gear for my carrier (stock '61) I would install it. As it is, a 3.08-3.36 gear is livable on the open road and fun to drive.
You can get a brand new Richmond ST-10 in any first gear ratio you want for right at 2k. The steeper the first gear, the weaker the box. Paul at 5speeds.com is the guy to see for a lot of this stuff....he got me some upgraded Japanese sealed bearings for my ST-10 when I rebuilt it in 2019. Not a hard job. Just need a press and some patience.

My split window would have been in that boneyard "back in the day" after the wreck. But now they are rare classics and the expense to resurrect them is well worth it. A couple pics of the "incident" that I don't think have ever been posted heretofore. The dickhead in the yellow traffic vest talking to the cop in the second picture is the uninsured, undocumented @hole that ran in front of me in the Escalade. I was carruing concealed that day and the ambulance driver wouldn't load me up with a firearm so that cop took the Ruger LCR into custody and returned it to me at my house the next day. The Winter Garden police were top notch.

All good info, as usual from you, Jeff.

With a total ratio of 11.5 in first gear, that '61 ought to leap away from a dead stop. I'll guess that you often don't bother with first gear?

If my car had a highway R&P ratio, I'd almost surely stick with a 4-speed, and I might very well do so anyway.

The sidepipes that some previous owner installed on this car have got to go, but that's a separate issue that would only be lessened somewhat by getting the revs down on the highway. Not enough of a solution. Getting the car back to under-car exhaust with reasonable mufflers would likely leave me content to stick with a WR gearbox and the 3.70 R&P. I, too, am an old-school 4-speed/Hurst guy at heart, and I don't presently envision doing very many hours-long runs at highway speeds.

If the T-10 were in great shape with no issues, I think it'd be a no-brainer to leave it alone. But, since it's going to need some work, and that work's going to be easier before the exhaust gets put back under the car and would then be in the way of the transmission R&R, I've held off making the conversion to under-car exhaust.

I think I now have everything on hand that's required to do that conversion. A full 2.5-inch exhaust system from Gardner, all hangers, tailpipes, all four heat shields, bezels, filler panel, fender extensions, rocker panels and associated screws are now stashed away awaiting the day. I never listen to the AM band on the radio, so I probably won't bother with the various ground straps, and I haven't ordered them.

Getting back to the decision that I've not yet made, you've added an option that I'll give some serious consideration, with the ST-10. Do you know if it uses the same driveshaft yoke as the old T-10 that's in my car now? And, do you know if the Hurst Competition Plus that's now in my car is a direct bolt-on to the ST-10, as I'd guess it might be? Are there any other interchange issues that I should be aware of between the circa 1961 T-10 and a new ST-10?

Thanks for tossing this out for consideration. Greatly appreciated.

Live well,

SJW

Damn, Frank. Those photos are painful to look at, but it's good to know that the car got put back together as good as new. Are you fully recovered from the injuries now? I'm sure you miss that car in no small amount now that it's being enjoyed by somebody else.

I'm sure you're right that if that crash had occurred back in the day, when the car was four or more years old, but nowhere near its collector status of today, it would have been totaled. Another argument for carrying a good Agreed Value policy on these vehicles. With an agreed value that's set high enough, it pretty well ensures that these cars will be repaired and will live to see more miles, instead of becoming parts donors.

Guessing you saw what PaulyWannafly has done to rebuild JoeC's Tripleblack '65 after its horrific crash?

Live well,

SJW

SJW, the ST-10 uses a TH400 type of rear yoke, and the input is fine spline, unlike the early T-10's. So you'd be looking at changing the clutch disc and the trans output yoke. There are adaptor plates to mount the Hurst shifter to the ST-10, which has less mounting holes on the tailhousing than the old T-10's. (three vs five holes) I feel your pain on the side pipes.....I never cared for them on Sting Rays, as I feel it clutters up the clean lines of the car. Not to mention the performance sacrifice over a regular under-car system. The only reason I rebuilt my ST-10 with the stiff first gear was because it's a 904 high nickel iron case (super strong) with the good gears. First gear in my car is about useless, unless I was doing parade duty (which I don't). I usually start out in first and shift right to 3rd. With the 383 under the hood, I drive around town in 3rd and 4th gear pretty much all the time. I don't even bother getting on it in first gear, which is the weak link in the trans. When I get on it in second or third, the rear end kicks out as is. (bias ply skinny 6.70-15 tires)

Thanks for the additional info, Jeff. I'd be replacing the disc, at a minimum, when the gearbox would come out. Probably the PP as well, and a resurface of the flywheel, if indicated. Do you know if the external dimensions of the ST-10 are identical to the vintage T-10, such that there would be no issues with respect to fit within the tunnel of a C2?

Gotta say I'm curious as to why you chose the first gear ratio that you did for yours.

Live well,

SJW

SJW, my car was a long-abandoned airplane hangar find and that's the trans that was in it. I may at a later date install an ST-10 or Muncie with a 2.52-2.66 low gear. As it is right now, my SECOND gear, at 2.20, is the same as FIRST gear in a close ratio Muncie M-21.
I would say dimensionally you should be just fine. Mine is a '61, but no modifications have been made to the floor or shifter porch to accommodate the ST-10 and Hurst shifter. My shifter runs right through the stock shifter plate bolted to the floor, using a Hurst adaptor to mount the shifter to the trans. If you want to go with a Muncie 4 speed, Tom Parsons has all the info. Pretty much a bolt-in with a couple of cross-member spacers. The old T-10 is weaker than a Muncie or an ST-10 trans, so either will be an upgrade to your car. Here's mine, with an early '60's Hurst 9" curved shifter on the ST-10.Attachment 67973