It seems like I have been working on more and more transmissions lately. While assembling an M-21 the other night I was thinking about all of the little tricks and custom mods that have been done to 4 speeds over the years to make them more track friendly. I learned what I know from my father who spent the better parts of the 60's, 70's, and 80's on a drag strip. He ran Muncies and T-10's until better sponsorship opened the door for a Doug Nash 5 speed crash box, and then on to a Jerico and eventually a Lenco. The latter three trannys were purposely built for racing but not so much for the Muncie. From him I learned how to make these work for me at the track but I know there is way more info out there. So what is everyone doing to make those Muncies and T-10s bang through the gears on the track?
I have found that some of my biggest improvements have come from spending a ton of time making sure that my shifter linkage is perfectly adjusted with no slop,use the steel bushings from the Hurst kit,not those damn nylon ones,and make sure your clutch linkage is working perfectly and smoothly,and is adjusted to engage just about a quarter inch into the travel of the pedal,making it lightning fast.I also fabbed a bracket and added another return spring to the linkage,which didn't really seem to increase pedal pressure much at all,but makes the pedal snap back nice and fast,so the thing will shift like lightning... As far as the clutch,I went with a Ram sintered metal disc.I have been 100% happy with it. I believe Liberty installs synchro rings with 1/2 as many teeth on them so they will engage more freely at 1/2 a bazillion rpms....but you have to make sure all the supporting cast is up to the job.
You should use a Super Shifter with the high bracket and straight rods. You can leave the energizer springs out of the synchros ..Put it together with heavy grease holding the dogs in place. Eventually you will crack or burr the blocking rings though. Then it's time to toss the brass out and slick shift 2, 3, and 4th gear and sliders. Race track only!!
All good info guys. I just thought I had it all figured out untill I started running a Vertigate. Then I had to start all over and re-think how I was setting up my sliders and syncros. Every now and then I still have to wait for engagement for just a breif second but I'm getting there. Next project is going to be the one that everybody has searched for at one point in their hot rodding career, building a 4 speed that can shift well on the track but still be semi street friendly. I know this is trying to combine two things that are 180* apart, as well as something that has been beat to death by hundreds of people but what can one more hurt!
I run at the Dry lakes and Bonneville with a Muncie close ratio transmission. Last year the tailshaft bushing got hot, and came loose. I found it nearly falling into the tailshaft. I have since installed a new bushing Locktighted it, and drilled the tailshaft for a Zerk fitting. I pump in a little Mobile 1 wheel bearing grease and so far it has been ok. I ran 208 mph in my Studebaker, pretty good for an old guy and a home built car..
208, thats not too shabby! Good solution for the problem, did you concider machining out the extension housing to accept a needle roller bearing? Just a thought.
I have always felt that Muncies were better road transmissions than drag units. An upgraded center support plate I think is a worthwhile upgrade if your going to work them hard.
I learned through years of running four speeds,you need a slipper style clutch or you WILL break the trans!!!I have been running a McLeod Soft-Lok clutch against a Jerico now for 5 seasons,was lucky to get 2 seasons with a sintered iron puck style against a Liberty Pro-Shifted transmission!! ROY.
Probably the most common muncie failure is shelling the input / countergear . Usually this is due to the case being stretched [hammered] at the front countershaft hole. The way I've repaired these is to bore out the case about .500" [index off the back hole] then turn a steel bushing the same thickness as the case w/ an interference fit into the case & a lesser interference fit for the shaft. Done properly , this strengthens the case plus you've also saved it !! dave
Ok here's one for you guys. We all know that if you are using front motor mounts that you need to use a bellhousing with mounts for the rear support and let the transmission hang, but if you use side engine mounts you need a crossmember under the trans. So my question is, If you have front engine mounts and run a scattershield instead of a bellhousing, could you ditch the bellhousing mounts and run a rear crossmember?
I would say you could get away with it on a Chevy if you babied the thing around. In my opinion, that's not enough support for a performance vehicle with a stick shift. I would build some kind of side mount system for the engine block...if you have the bolt holes there.
What makes the most sense to me is to weld some ears on the ansen scatter shield since its forged and utilize the crossmember that the original bell mounted to. The reason I asked the question is that an old timer was telling me that they used to mount the motor in the front to aid in header clearance as opposed to the side mounts, and just run a rear crossmember under the trans. I don't like that setup but he insisted that with a scatter shield it was strong enough. Still doesn't sound good to me though.
What about if you are running a muncie behind a 56 Olds rocket? I know the stock set up had mounts on the fron and ears on the bell housing, but with hurst mounts it spreads out the load and on the rear all the adapter plates do not have mounting ears. Can you get awat with a standard rear mount with the hurst mounts in the front?
I have a 55 and 56 Chevys with Lakewood bellhousings that bolt up to the stock 55-57 bellhousing mounts. They have a flat area formed in where the mount ear bolts to the bell.
Thirty or more years ago, a friend of mine told me about Long Shifters (Long is a BRAND, not a length) & how they hold the patents for all that makes a shifter good .....Hurst, Mr Gasket & others have only been able to make & sell shifters by using a design that doesn't infringe on Long's patent....but at the expense of functionality. When I told another friend of mine who was running an o/t Nova, and having continual problems with his Hurst shifter about Long's, he ordered one up over the folllowing winter, and was deliriously happy with it when it showed up! (and was even happier after making some passes) LONG SHIFTERS http://www.gforcetransmissions.com/shifter_4speeds.asp Not sure if it was the previous winter, or the winter after, he contacted Liberty's Gears, and after speaking with one of the fellows there, ended up sending some T-10 internals all the way south of the border for them to modify. And again, after assembling & making some passes, he is more than happy with the improvements..... Liberty (& others) offer race prepped versions, as well as parts to make your trans shift better than a stocker. However, not all versions are street friendly. LIBERTY's GEARS http://www.libertysgears.com/
Springs = item 19 here? http://image.highperformancepontiac...1_02_z+pontiac_muncie_transmission+manual.jpg I read of the spring removal in a Hot Rod Muncie article by Pepe Estrada back in the 70s. He said it >>should<< work in Saginaws too, so I left them out of my late model (66 and up) Corvair trans. It clashed terribly when shifting fast or slow, so I put the springs back in.
In regards to the rest of the post, T-10s ... weak junk. ST-10 way better, problems with the side covers for shifting on the few I have had experience. But many first gear ratios. Very rare Speed shop ones the best. Full cast iron cases, mid plates and tail shafts. Some were Slick shifted or Dog eared, No syncos , good for 3/10s in the quartered mile. Sucked on the street. Old Muncies, Just as strong as the ST-10s. I have been running a Muncie m-21, I converted to a M-22-w for the last 8 years. A super transmission. Consistent 1.5 60 foots, big wheel stands in first and second. Just waiting for the $$ to upgraded to a M-23 better transmission. Jim
What kind of mods should be done to a M21 to make it hold up to heavy abuse. Posted using the Full Custom H.A.M.B. App!
Yep modified syncros, straight cut gears, I have even seen them with the gears opened up so they would slop together better. But at that point they become useless on the street and are just a crash box.
Depends on what you consider heavy abuse, if you want to drive it hard, race it sometimes and have it last then the list is simple and tedious. Everything polished and deburred including the inside of the case, tolerances as close to perfect as possible, heavy duty shift forks if you can still buy them, if I recall Moroso used to market some, ductile iron or something lie that. Shifter adjusted dead nutz. I don't know if you can still get it done but we used to get gears micro plated. With micro plated gears you could run thinner oil. An oil cooler on a transmission that is going to be hammered over a long distance also helps. No help? maybe someone has better info for you then that.
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