My original comment for the question of "Wide or close ratio?" would have been a wide ratio so as to bring the revs back down into the low RPM of a BBB. But now.... there are a lot of factors, one being the cam and its powerband and the rear gears as well as the overall healthiness of the powerplant. I went with a wide ratio M20, but there is times on the street that I have to cruise at a higher RPM and stay in third as the 4th gear RPM at that constant speed is to low and the car wants to surge. Sorry I cant be more specific about MPH and RPM this occurs but its been 3 months since I have had the pleasure of driving my GS. But I beleive anything less than 1500RPM causes the surge. Surge may be a polite term also. I am running a fair amount of cam (TA 296-08h) with 3.42 gears. I also calculated the drop between gears and the wide ratio wasn’t as wide I as I would have guessed. I think a close ratio would be better for my application, the loss of some ratio in first may be a good thing for me, as with drag radials I can light the tires up at will any time in first and the lower half of second if I just mat it. This is one of my big concerns to installing an even steeper first geared Tremec. I compared the RPM drop of a Tremec a long while back and if I remember correctly it was spaced more like a wide ratio than a close. I would like to exam this more in this thread. If someone could input a M20, M21/22, ST10 and a TKO into a spreadsheet and we could compare the RPM drops between gears at redline. Also, Bob (buickgsman) you have real life experience with a M20 and a TKO in the same car with the same engine and rearend combos correct? Please share the differences such as Launch, going full throttle from a roll and streetabilty.
Hi Greg, I'm thinkin' just keep what you have and shift to a lower gear if your RPMs get too low/out of the power band. Thats what shifting the 4-speed is all about, right? Having the gears to keep the revs in the power band so you are ready to rip the tires at any moment :TU: Your comment about the tremec is true- with a 3.27:1 1st gear it seems kind of pointless unless you have a highway gear in the rear; then the OD is really pointless with an engine that is not set up to run at a lower RPM. I was really excited when they came out with the TKO 600; better 1st gear ratio and optional .82 OD makes more sense to tighten up the ratios than to have them so wide as the TKO 500; 3.27 1st and .6x OD seems realllllyyy W I D E ! Ted
Ted, hey whats up, Burton and myself want to get down your way soon. Actually my problem is more due to traffic and matchng my RPM's to in town speed limits. For instance rolling into a small Indiana town for a cruise in one evening. As I slow down to the speed limit I have to run a gear that puts me at a higher RPM than I would like to be at so as not to have the 3" flowmasters drawing attention to us, but to upshift puts the motor to near that magic 1500RPM minimum threshold. Seems if the ratios were closer together then i would have a better selection. But after compairing the precentage drop of a M20 to a M21/22 there is no difference except 3 to 4. M20 25% 22% 32% M21/22 25% 22% 22%
Greg, I can't really speak to "launching", but the car accelerates fantastic, cruises nice, and the TKO shifts very well. I used that muncie for 1 maybe 2 seasons before I got ants in my pants and started swapping everything but the kitchen sink into it. I can't say that I noticed a huge difference. It might accelerate a bit stronger, but thats about it aside from the overdrive, which is super cool. I've literally had the car going 150mph and the car wasn't revving high at all. It is nice shifting into the overdrive. I can do 60 mph and I'm probably cruising at 1400 rpm. One thing i don't worry about is breaking the trans if it does launch hard, but the tires break loose way before any type of hard lauch would happen. Again, the only downside to the whole Tremec swap is the hole in the floor. That made me sick cutting that, but you really can't tell at this point, so no harm done. If I was working with a a real stage 1 4 speed GSX, I would probably not have cut the hole and left the Muncie. Would I do a TKO again??? probably not, but i kinda want an automatic car next anyway. And if you are in the neighborhood, feel free to swing by and take it for a ride to test it out for yourself. :TU:
Between an M-20 wide and a M-21 close the difference is pretty minimal ratio wise compared to some of the other transmissions that were made. The m-20 would actually be considered a close ratio compared to most other transmissions. The M-21/ M-22 was one of the closest ratio trans ever built by the big three. I prefer the 2.52 1st gear over the 2.20 for a heavy car like ours. I am quite happy with my M-20, 3.42 gears and 27" tall tire. I have looked at other transmission options but the 1st gear always seems too low to the point of being unusable, and I am not quite comfortable going down to a 2.20 1st gear with the M-21/M-22. It would be awesome if the TKO could be had with a 2.6-2.8 1st gear and a .82 OD. With big torque engines like ours it seems pointless to run a 1st gear of 3.27. o No:
I have a narrow, and you wouldn't want one as you really have to slip the clutch to launch good. Narrows were originally made for road racing, where launching wasn't a concern and they wanted the engine to always be operating in a narrow rpm band. My next will be a TKO, hopefully with around 10:1 overall in first.
Greg, a possible alternative comes to mind. Others will scoff, but what helped me was Rhoades Lifters. They help with that big cam bucking at low rpm and give a good bit more low end torque too. Just a suggestion. Todd
I'm in the same boat. Our setups are basically the same, turned up BBB, M20 3.42s, 27" tires. between speeds 25-35 in fourth the motor is still surging and loping a bit. the third gear downshift bites since the motor has so much leverage against the car- let off the gas slightly and you almost go through the windshield. 4th bites because the motor is loading up and chugging. I'm not willing to change my combo just yet, I love the power band. I'm going to try a few things. Try running a boat load of vacuum advance from intake vacuum. slighty shorter rear tire rhoads lifters as mentioned stepping up to a 3.55 gear Thats about all I can think of really.
After 4 months of not driving the car it was nice to finally spend 2 hours just street cruising last night. There is nothing with my combo that I can not live with on the street. I started this thread just to see if there was a better solution. What have we discovered. This motor makes enough power that a 2.20 first gear would not affect driveabilty what so ever, it takes nothing to get it to roll from a stop. Actually not having to shift out of first quite so soon in traffic would be a plus. Would this affect the 60' times, I dont know since it just lights up the drag radials at will at full throttle in 1st gear. But probaly so. The biggest driveability issue is the 3 to 4 shift. In normal traffic driving following cars i typically shift a 2300-2500 RPM (1-2 and 2-3) but the 3-4 shift must occur at 3000 RPM minimum and then i can sustain a constant cruise in 4th. If I can then obtain just a slight bit of acceleration everything is cool. Now if Immediately after the 3-4 shift occurs if the traffic maintains a constant speed i am still all right but on the border, if i must coast at anytime I then must downshift again or roll with the clucth in. Again this is not a huge deal or any reason to change my combo, I can live with it, It's just rolling into Mayberry and having to cruise Main Street at 2800 RPM constant gets a lot more attention from Barney than I like. Now if I had an M21/22 the 3-4 percentage drop is 22% compaired to the 32% of the M20, the issue would be less so. The only difference in the wide ratio and the close ratio Muncie (as far as wide and close is considered) is the the percentage drop of the 3-4 shift. The 1-2 and 2-3 drops are 22% for both the M20 and M21/22. Obviously the gear ratios are different between the two. I had not thought of the Roades lifters, that is a good suggestion. I am running vacuum advance, how much I dont recall. I have a 26" tall tire.
The swap to a close ratio would be a band aid to the real problem. Instead of fixing the chugging in fourth, you want third to be higher so you can cruise in that gear. How much highway driving do you do? Maybe a close ratio with a set of 3.73s will fix ya up.
Don't underestimate the difference between a 2.52 first gear and a 2.20 first gear. True your motor makes enough power to overcome the lack of gear but switching to a 2.20 first gear would be like swapping your rear end ratio from a 3.42 down to under a 3.08. I don't know how happy you would be about the way that feels when you let out the clutch in first gear and the engine is way below it's powerband.
This is the way to fix it...throw in a set of 3.73-4.11 gears and get a Gear vendors overdrive!:3gears:
Todd your correct it would equal a 2.93 rear gear set ou: Its been a while since I done the math, didnt sound like much going from 2.56 to 2.20 until you do the math. Tim nothing against the Gear Vendors but I would go Tremec first, I am not afraid of no saw, I cut the floor once, I can do again. Joe, your suggestion would be the best overall solution. The true problem is the 32% drop at the 3-4 shift. To only change the rear end gears the same problem would occur just at a different MPH. Now so far all we have talked about is drivability, which is a big part of a street/strip car, but like I said I can live with it and for all purposes this year I will, because I am having way to much fun with my 4 speed. But i guess from the strip point of view the wide ratio is best because of the better multiplication factor of the ratios. I always thought the wide ratio was best for our low RPM Big torque monster engines because it would drop the RPM lower at each shift than a close ratio, but since that is not the case until the 3-4 shift occurs this should be less of a factor. Ok I am back to my original answer Wide Ratio.
Greg - this won't answer your question but .... What drag radials ?? If they're BFG's .... SWITCH to Mickey Thompson ET STreet DR's. Nite and day difference, trust me. ....as for the rest of the thread I find it very interesting as I've yet to decide what tranny the new car is going to get. I have a fresh M21 ready to go but that never stopped me from ...ahem...whitching gears mid-stream. Im actually liking the GearVendors Idea behind a 4-speed. I need to research that a bit more. From what Im reading, it seams your 4th gear / rear end / tire diameter final ratio is too low for lugging around town ... and dropping it into third puts the rev's too high ?? certainly the cheapest of the 3 items to change that affect final ratio is a tire change which brings me back to my first point :Brow:
The answer sadly is both - in the old days it was one or the other With a 6-speed (they are even coming out w 7 speeds) you get it all Rear end gears are certainly a factor If you are dragging around a 4:11 RE you don't wan close ratio in a 4-speed...
Yes they are BFG DR and older ones at that, That is a great suggestion as I am not that adept to soft shoeing and peddling it. I like to mat it and go. Pretty much, Still let me say its not something that I cant live with. Without any traffic you would never notice it, its just trying to match traffic and that can be difficult in anything. I was just thinking there may be something better. It really only is a problem when trying to be stealthy, maybe I should just realize that it is harder to do in a 4 speed BBB :3gears:
The percentage drops of a TKO600 are as follows 1-2 34.1% 2-3 32.2 3-4 32.2 4-5 36.0% Now that is a wide ratio compaired to a Muncie, this is equal to the 3-4 shift % drop of the Muncie that is giving me the issue now.
Greg, I run the 255-60-15 27" tall MT drag radials and with my combo I can't hook at all in 1st gear. I'm hoping boxed control arms, and airbags will help in that area. I also thought the MTs would solve all my launch woes and they did not. ou:
