Would anyone change a muncie 4 speed to an auto overdrive ? My 67 RS needs a different gear in the rear because I am guessing its a 2.73 or 3.08 and the first gear in the trans makes it really tough starting off. Too many options : 5 speed and 3.55 gear, keep 4 speed and go with 3.36 gear or change to an auto overdrive ? And yes money is a factor.:confused:

heres my story
4 speed with 2:73 and it sucked balls and i aslo had 28" tall tire so it REALLY sucked

i got a 3:55 and kept my 4 speed and 28" tall tires and it still is kind of sluggish but i think its my motor that is sluggish and not the gear and stuff - - $600 for gear and labor, took 2 days but thats here in N,C

at 70 im running 3000 rpm....at 50-55 mph im running around 2200 rpm

i just bought some 27" tall tires and a new double pumper carb and ill be putting them on next week and hoping that will help it out a little

if i could do it again i would get 3:73 or the next gear up

5 and 6 peed i think require a little bit of modification and i didnt want to start cutting up and having to buy different parts and doing stuff to my car

i would still like a automatic though, but i somthing about the 4 speed i like more

Would anyone change a muncie 4 speed to an auto overdrive ? My 67 RS needs a different gear in the rear because I am guessing its a 2.73 or 3.08 and the first gear in the trans makes it really tough starting off. Too many options : 5 speed and 3.55 gear, keep 4 speed and go with 3.36 gear or change to an auto overdrive ? And yes money is a factor.:confused:

Some people told me a TKO-600 was overkill for my car (I have 3.31). I am so glad I didn't pay attention to the naysayers. This will probably be the single most important investment I've put into my 69'. There are NO modifications to speak of if you you've already got a 4spd tran. You MIGHT...might have to cut a tiny little piece of tunnel (you can avoid this by paying more for their offset shifter, but it's nearly $300). I would think that if you went with an auto you're going to end up paying damn near what a whole TKO kit will cost....and the TKO is brand new. No chances on "how well was it rebuilt" or "does it really have 1K miles on rebuild" or "was it done by someone competent".

All new, great support staff, and a great value, imho. And if it helps...I'd never installed a clutch let alone, a transmission in my whole life. It did kick my butt, but only because I was totally green. I could do it again in 10-12hrs. I have all the same gears I had when I had my 4spd, but I have a much smoother shifting car...AND that .64 5th gear. I can cruise at 80mph and @ 1900rpms. And yes, it'll definitely save gas! So again, I have the best of both worlds. I can get on it when I want...and cruise in comfort when I want.

And to think.....I almost got a new M20 instead :boring:

Thanks. I just got back from my gear shop. They removed the diff. cover and confirmed I have a 3:08 gear. Sounds like the ideal set up would be a 3:55 or 3:73 and a 5 speed for overdrive. Alot of $$$ to spend for this upgrade !:yes:

You could try just changing the rear end gears first. I have a 3.42 gear and a wide ratio (M20) Muncie in my ’67 and it pulls great from a dead stop in first.

Is your Muncie an M20 or an M21? A close ratio M21 with a 3.08 rear end would be sluggish in first gear.

Dont know. How can you tell an m20 from an m21 ?

Dont know. How can you tell an m20 from an m21 ?

It gets a little complicated if you are just looking at the two. It depends on the year. You usually will be able to look at the 5 to 6 digit number running veritcally on the main case. the last letter is A: M-20, B: M-21 and C:M-22. They don't always have the letters on the end though. The next way is by looking at the input splines and the rings or no rings depending on the year. I won't go into that unless you ask. The main way by driving is that the M-20 has a lower 1st gear, then 2nd and 3rd are close together, then 4th is a little farther apart. The M-21 and 22 are close ratio so all the gears seem the same distance (RPMs) apart. Problem is that with a 21 or 22, it's harder to start out if you have 2.73's or 3.08's. Can be hard on the clutch and requires lots of R's to get it going. The 21 is a stronger trans though, and the 22 is the strongest.

I hate my automatic. Good shifts from 1st to 2nd but 2nd to 3rd is not instantaneous. When I am cruising slow, I feel like a jack off having to shift it into neutral just to blip the gas. If you have a stall less than 3000 with around 330 horse and less than 355 gears, you wont be impressed with the launch. Right now my car is on a Kwik lift with the 350 turbo ready to be pulled and a m20 waiting in the wings. I would love a 5 speed but the m20 I have cost about three+ times less. Automatics are good for the strip but I get there once every couple years for a couple passes. Automatics are nice for traffic.

I hate my automatic. .............
........Automatics are good for the strip but I get there once every couple years for a couple passes. Automatics are nice for traffic.

I almost gave up looking for a 4spd. They're hard to find at a decent price. And for a BBC 4spd, forget it. Most of the sites I looked at...and in my price range....90% were autos for sale. It's funny, but with any newer cars, the autos always cost more:).

I wouldn't trade the 4-speed for a Auto -- I went the other way and traded out my TH350 for a 4-speed :)

If my reading about on your other posts is accurate, you've got a 327/275hp with an unknown Muncie 4-speed and 2.73/3.08 rear gears. It also looks like you enjoy stirring the gears with the stick, but launching is a PITA. It also looks like you're considering a clutch replacement.

If you're planning on dropping the trans anyway for a clutch replacement, I'd look into swapping out the trans for another 4-speed with a wider ratio set. You may be able to get your current Muncie rebuilt with the wide ratio set (not sure on cost), but otherwise, Muncies can be a bit hard to come by (and expensive), but a Super T-10's are plentiful and reasonably priced. You can get the ST10 with a 3.42 1st gear, which will give great off-the-line performance. Probably a better choice would be the 2.88 or 2.64 1st gear ST10 since they're a bit stronger. I'd think any of these would be fine behind a 327. Note that you'll need a 26-spline clutch if you do ST10 and will probably need to tweak your shift linkage/mount a bit. You should be able to get a decent rebuilt ST10 and the parts for something like $1k. Note if you ever decide to go with a TKO 5-speed, it uses the same 26-spline input, so you can use the same clutch disc as the ST10.

Shift Yourself!

Thanks. Your info is a great help. I had a powerglide car before this one and it wasnt as fun to drive , better in stop and go traffic though. Is there enough difference in a 3.08 gear and 3.36 to justify the change. The 3.55 may be tough on the interstate 70 + driving. I will check the numbers on the trans to see which one it is.

Checked the tranny today, looks like an M 20 . Had the A at the end of the 5 digit # on the side of the case.Would you run a 3.08 with it , or step up to the 3.36 or 3.55 ? Not racing it just a driver .

I too have 3.08 and an M-21 close ratio. It is a bit sluggish starting out in 1st but really goes after that. I had a pretty built up 327 but I think that setup made me loose alot of bottom end. I am planning on going with a 3.23 or 3.42 once I drive it a bit with my newly rebuilt engine to see what suits the cam best. I used to get 19-20 MPG on the hwy with the previous setup. I wouldn't trade the 4 speed for anything. I think it is important to decide what you want to do with the car. If it is a daily driver with lots of highway then perhaps a 5 speed overdrive would solve your issues.

Checked the tranny today, looks like an M 20 . Had the A at the end of the 5 digit # on the side of the case.Would you run a 3.08 with it , or step up to the 3.36 or 3.55 ? Not racing it just a driver .

I would think you could up the gears just a bit then (3.36). Or you might look into doing a few engine mods like an intake and cam to increase the torque on the bottom end.

I wouldn't convert to an Automatic...... I'd say that 4-speeds are much rarer and therefore worth more.
IMO.

Somebody needs to speak up in favor of the OD automatic.

I keep toying with the idea of a TKO-600. Then I hop in the car and drive it. The 2004R is awesome. I've got it perfectly dialed in and I can cruise around town with my left arm resting on the door and drink a pop or eat a sandwich or hold onto the glovebox door to keep it from rattling with the other. I feel fairly certain the car is quicker with the auto than it would be with 5 speed, and not as tough on parts. Plus, I spent over $2K on it, and have a hard time justifying the expense of a 5 speed with a perfectly good OD auto.

The only time I really get the itch for the 5 speed is on the open road. It WOULD be nicer there. Maybe someday.

I checked the numbers on my 4 speed and it has a 2.52 first gear, 1.88 second, 1.46 third, and 1.00 4th. Would a 3.08 rear be acceptable with the 2.52 first gear and would a 3.36 make much of a change ? Maybe 200 rpms at 70 ? I do have a new performer rpm air gap intake and holley 660 street avenger carb. Otherwise stock. I would like a little more gear to get it rolling but not kill highway cruising. Yea, an auto w/overdrive would be nice at times. I will try a few things before I give up on the 4 speed.

upping the gears a little does nothing but move your compromise.

Fact is, with only 4 gears and no torque converter, perfect ain't gonna happen. you'll have a compromise, either at the stop light or on the highway.

No way would I spend what will turn out to be a grand to change the rear gear ration 10%. And yes, it will be a grand, or more. New gearset, couple hundred. install kit, 50-75, bearings and seals, another hundred. While you're in there you'll decide to upgrade to a posi (snowball effect will kick in) AND you'll find the bearing surfaces on your axles are worn $450 plus $200 for new axles. Plus if you pay someone to set it up, there's another couple hundred. For a 10% change!

Your 3.31 will be fine with the tko. With your motor as it is, I'd go with the TKO500, with it's lower first.

If you want to lose your third pedal, then put in an OD automatic.

And don't forget, your muncie and shifter are worth solid coin. I sold mine to a member here for $800 in less than a week. A big help offsetting the TKO cost. If you go automatic, your bellhousing and flywheel are worth good money too. Note the Z/28 used the same parts. Be sure to put that in the ebay ad.

You are absolutely right. Our gear shop told me about $1,200.00 for a pos unit , gears, etc , installed.I need to leave it as is until I choose transmissions for an overdrive.

There is a "cheap/cheaper" solution compared to changing out your transmission & your tail end gear at once. Consider a Saginaw with a low first gear. I know a lot of people frown down on the lowly Saginaw but; it would get you off the line a lot better & save $ thousands $ compared to your other options. It'd also give you a lot more time to figure out what kind of trans/tail combo you what to invest $3,000.00 to $5,000.00 in.
http://cgi.ebay.com/ebaymotors/69-Camaro-Firebird-4-Speed-Saginaw-Muncie-67-68-70-GTO_W0QQitemZ290154815928QQihZ019QQcategoryZ34208Q QssPageNameZWDVWQQrdZ1QQcmdZViewItem

Great idea ! That is a much better first gear.

There is a "cheap/cheaper" solution compared to changing out your transmission & your tail end gear at once. Consider a Saginaw with a low first gear. I know a lot of people frown down on the lowly Saginaw but; it would get you off the line a lot better & save $ thousands $ compared to your other options. It'd also give you a lot more time to figure out what kind of trans/tail combo you what to invest $3,000.00 to $5,000.00 in.
http://cgi.ebay.com/ebaymotors/69-Camaro-Firebird-4-Speed-Saginaw-Muncie-67-68-70-GTO_W0QQitemZ290154815928QQihZ019QQcategoryZ34208Q QssPageNameZWDVWQQrdZ1QQcmdZViewItem

If you decide to go this ^ way, I have the Saginaw I took out of mine...when I put a TKO 600 (3.31 rear) in mine. But...I wouldn't do it.:)

You can get an even better 1st gear than the example I posted earlier. This guy sells them fairly frequently on ebay. They are rebuilt with a 3.50 first gear. That would give you a year or two (jumping of the line) to save up & decide about all that other stuff you where thinking about.

http://cgi.ebay.com/ebaymotors/SAGINAW-4-SPEED-TRANSMISSION-MUNCIE_W0QQitemZ170138688202QQihZ007QQcategoryZ337 33QQssPageNameZWDVWQQrdZ1QQcmdZViewItem

You can get an even better 1st gear than the example I posted earlier. This guy sells them fairly frequently on ebay. They are rebuilt with a 3.50 first gear. That would give you a year or two (jumping of the line) to save up & decide about all that other stuff you where thinking about.

The TKO 500 has a 3.27 first. Just sayin'.......:thumbsup:

The TKO 500 has a 3.27 first. Just sayin'.......:thumbsup:

Hey... I thought I said that! :thumbsup:

The TKO 500 has a 3.27 first. Just sayin'.......:thumbsup:


I know... But if he also wants to (eventually) change out the rear gear, there ain't no use spending big bucks on a 500 that ain't gonna work (very well) with a lower rear gear in the future. I wouldn't spend the money on a TKO until I had my rear-end sitting the way I want. {*!*}

Probably need a 3.55 or 3.73 with aTKO 5 speed. Or any auto overdrive.

Fwiw, I bought a 3.50 low gear 4-speed Sag off a guy in St. Charles a while back for like $145 for my old '80 C/10 P/U.

You want a good 3-speed Sag that's also a 3.50 until you figure out what you want, just hollar..

pdq67

Here's a list of gear ratios for Saginaws so you can tell what it is in an instant. I had the one groove version in my car for years and beat on it pretty hard without it blowing up. I wouldn't do too many top fuel burnouts with the 3.50 first gear version though. The torque multiplication is huge with that low of a first gear. Saginaws were basically three speed transmissions that they stuffed a fourth gear into. They weren't made for a lot of torque.

On the other hand, if all you want to do is cruise around town, the 3.50 1st gear version is great. The first 3 gears are all low to get you going quickly and then 4th is 1:1 like everything else. It feels kind of like a 3 speed with an overdrive. ;) I just put one in my car till I can save a few bucks for the TKO 500 swap.

Saginaw 4 speed number of grooves (lines) on input shaft

No Grooves
2.84
2.01
1.35
1.00

1 Groove
2.54
1.80
1.44
1.00

2 Grooves
3.11
2.20
1.47
1.00

3 Grooves
3.50
2.47
1.65
1.00

Probably need a 3.55 or 3.73 with aTKO 5 speed. Or any auto overdrive.
That REALLY depends on the torque curve of his engine. Many motors are perfectly happy pulling a 2:1 or even lower overall gear on the freeway.


What's the overall gear ratio in high in a T56 fourthgen?

My 93 vette has a 700r4 and 2.53 I think rear. The darn thing will lock the convertor in OD at 40 mph, that's around 800 rpm. It don't like it much, bucks a lil, and I often pull her back to third to get the revs up to 1200... but that's the way chevy built her.

Think I will start saving for a 5 speed. If I go to the trouble to pull the muncie out, something better has to go back in. Something I will have no regrets doing.

Think I will start saving for a 5 speed. If I go to the trouble to pull the muncie out, something better has to go back in. Something I will have no regrets doing.

You will not regret this wise choice. I took my youngest son for a drive today and was showing him the engine temp which was at 150-155 because I was driving on rural roadways at 50mph (well, for the most part :)), and the tach was reading 1400. It's unbelievable what a difference the 5 spd will make. Even at constant speeds of 75-85, the temp has not risen above 180 because I'm taching at 1900rpms! With my Saginaw, it was 200 at that speed, and only dropped to 190-195 when I'd get back down to 65-70.

1. Cooler running engine
2. Lower rpms
3. 5th gear BIG gas saver
4. Sounds quieter than idle at 50-60
5. 4x Smoother shifting than a Muncie/Saginaw
6. Makes long trips more comfortable (and doable)
7. You still have same basic 4 gears you used to have, plus one

Well worth the investment, imho.