Team Chevelle banner

4-spd vs 5-spd

5K views 41 replies 22 participants last post by  .183953 
#1 ·
Hi All,

I recently picked up a Muncie M20 to convert my '68 to manual and I think I have everything to make it happen, but I'm starting to second guess my decision and wonder if I should put a 5-spd in it instead. I currently have a 700r4, which we all know is a 30% OD and 1:1 3rd gear. Fourth gear in the Muncie is 1:1. I'm running 275/60/15 and 3.73s, I think it would be fun, but I'm not sure now if I want to have it run ~2500 rpm just to cruise on the two lane and probably ~3k if I ever hit the interstate.

Thoughts/recommendations on 5-spd units? It will likely never see a track, just a street cruiser. I don't need a bulletproof race unit, just something that will handle ~450 HP/TQ. Ultimately I'd like to do the Power Tour someday, so some fuel economy might be nice. I'm not apposed to a 'junkyard' swap either.

If anyone is interested in a clean M20, it could be bought. Recently rebuilt, I can send you the contact info for the guy who did it. I've got everything - new clutch kit, new flywheel, complete from bellhousing to tailshaft, Hurst shifter, etc. It's an early one, '63 I believe, 10 spline input shaft - I know, I know, not the most desirable of them all, but given it's been refreshed it could be nice for a guy like me that wanted a 4-spd specifically to street cruise and/or a guy looking for a '63 to do a numbers restoration. I'm thinking I only want to do this project once haha.

As always, I appreciate all the feedback, you guys are awesome!
 
See less See more
#2 ·
:cool: Take a look at a T-56 "Magnum (which is "better" than the regular T-56)." But, you're going to have to do significant surgery on the transmission hump. A T-56 Magnum transmission and all the doodads will see about $6,000.00 to 7,000.00, as I recall.

There are some 6 speeds out there which are even more expensive.

Between the hump surgery, my well-used left knee, and the overall cost I decided to stick with mu 700R4. Call me shiftless, but a manual is no longer viable for me.
 
#3 ·
I have a Muncie 4 speed m20 with 3.73s. Awesome in the street but sucks on the highway. I will be going to a T56 in the future when I get time and money. In my opinion a 5 speed does not satisfy my wants for an OD selection. It’s either too much of an OD or no enough. The 6 speeds give you both options and shift smoother too.
 
#5 ·
As Bruce said, T56 Magnum is major surgery. It is also a heavy transmission. I'd guess a good 40-50 lbs heavier than an aluminum case Muncie. The double OD is nice though

I think a good 5 speed is good if you don't want to cut your floors up. I think the Legend LGT-700 and McLeod 5 speeds are direct fit. Good luck getting an LGT though.

If you want to see how much cutting is involved, I made a bunch of install videos on you youtube channel.
 
#7 ·
I have 373s in my 69. Used to have an M21. It sucked on the highway. I found that is was the loud/ constant exhaust drone that was an equal problem with the on the high side rpm. Couple years ago I was able to get my hands on a brand new Legend 5 speed. Got lucky as they are hard to come by. Found a guy that bought one and never installed it then ended up selling the car he purchased the Legend for. Nice thing about them is no tunnel mods. Another 5 speed overdrive that does not require tunnel mods is the Richmond Super street. Paul at 5 Speeds has a video out about mods he does to the Super Street. Nice thing about a Super Street is it is almost a direct swap with a Muncie. So for those that already have a Muncie most of the equipment is reused. Used Super Streets can be had. Nice thing about the 5 speed and the 373s is cruising at 70 mph and turning 2200 rpm. I have found the 5th gear to be plenty of overdrive.
 
#8 ·
McCleod has a 5 spd isnt huge. Dont kno wmuch about it saw it in Summits catalog
You dont need a 6 sod. have one, nice to know its there but really dont need more than 5. And they arent cheap to do either

Junkyard ones are too old more than likely it will have issues so add on 1500 to rebuild it. Let us know..
I hear jody is good as posted above
 
#11 ·
You could stick with a 4 sp if you decided to change the rear end gear and then get a M23Z muncie best of both worlds with that set up.And probably close to the price of swap to a 5 sp.
 
#12 ·
I examined that option in pretty fair detail before I installed a 5 speed. I calculated that even with 3.08 rear gears and a 1/1 fourth gear I would still be turning about 2650 rpm at either 65 or 70 mph. Can't recall which one it was. So what I did was to go out on a lonely stretch of highway and ran my car at 2650 rpm for about five minutes. What I found was for my liking the exhaust report at that rpm was too much. Found it much better at 2200 rpm for sustained periods.
I agree that an M23z or even an M22z is the cats ass for a 4 speed. Just can't compete with an overdrive for highway cruising.
 
#15 ·
My budget and driving style doesn't warrant a 6-spd. Whatever I do, ideally it would fit in the stock tunnel. I don't mind clearancing a little with the ole BFH, but I don't have the tools or skills to be fabbing a new tunnel. I saw the McCleod in the summit mag this weekend and I'll check out the M23Z. I'll have to figure out what's available w/o major floor reconstruction and what I can afford. 90% of the time, it'll never see the highway or at least not for more than 30 mins in this area. I didn't want to do this more than once, but hell I said the same thing about pulling the rear axle when I did gears (and not suspension at the same time) and that thing was out 3 times before I was done haha. Thanks for all the input.
 
#17 ·
I have written about my 5 speed in the past and will up-date it with you.
I had an M20 with 15" tires and 3.4:1 axel. Highway RPMs were always in the 3000 area and it was not a nice driver car on the freeway. After research I bought a specially prepared T5 as shown in the photo.

On the plus side it was a form-fit-function as in NO cutting the floor, same bell housing, same transmission cross member, same drive shaft. Gearing is great with a 3.0:1 first gear, 4th gear is 1:1 and 5th gear is 0.6:1. Highway RPM's went from 3000+ to 1900. I love this combo.

On the negative side it has a 26 spline in lieu of the 10 spline in-put shaft. This means the clutch disc needs to be 26 spline nothing more, standard stuff for a clutch supplier. The speed-O drive is different but very doable. It is a top loader, I believe it is called, so the through-the-floor shift lever is not where a M20 is with its side linkage. I made an off-set bracket and in my 65 with the factory console the lever is now in the same position as with the M20.

Some will say it is too weak for a mussel car but that is not true. I have it behind a 383 with 400+ ft. lbs. of torque and it works great. I doubt that any transmission will last long if you power shift it. My transmission builder had the gears treated (cygroenits SP) I believe it is called and as this car is a driver and not a race car it works fine.

The long and short of this I would do this again without hesitation. This transmission did not brake the bank cost wise, so if this is of interest send me a PM and I'll connect you with the local transmission builder here is Seattle... Al
 

Attachments

#19 ·
Al,
I like it!!!!!!!!!!!!!!
It's not spinning high rpm through the gears that hurts a tranny, it's the hard banging on the gears that breaks them.
 
#18 ·
I have a 70 conv with a very healthy SB400-M22W-2.73 12bolt posi.
MOST people felt that with the 2.56 1st gear and a 2.73 rear, I would be slipping the clutch a lot. NOT!!!
The 400 has plenty of torque to get the car rolling from a stop--------------even on a slight incline.
I admit that it is not a rocket from a stop, but the trade off for low hiway rpm is worth it! Also, because of the 2.73 rear, I can stay in 1st and 2nd MUCH longer, which makes it great for getting up to speed quickly when getting on the Interstate.
Previously the 70 had an M20 and 3.07 12bolt. And nothing was wrong with either of those-------------I just wanted to have the M22 whine. So I bought an M22W gear set from D&L, built my own M22 and while I was under the car I swapped the 3.07 for the 2.73 which I had recently built.
With the 1:1 4th gear of the M22W and the 2.73 rear, it's very close to what many cars with a 5spOD and a 3.73 or 4.10 rear have.

I LOVE IT!
 
#25 ·
My 66 came to me and I drove it for 5 or 6 years with the TH350 and 331 gears. Max trip was 50 miles at 70 or 75 on the interstate. Loud and miserable.

So I skipped right over the four speed deal and tried a T5 with a .90 od. If fit with no cutting, but the Od was not much.

It proved my stick conversion, and a tko 600 found it way in there. Some tunnel tinwork, yes, but now it will cruise the interstate anywhere anytime and stay with traffic. And that's with a 373 gear upgrade.

So much more fun and useful.
 
#26 ·
I installed a Tremec TKO 600 in my 68 Chevelle last winter. It is powered by a 350 with an Edelbrock rolling thunder top end kit (E-tec 170 heads, hydraulic roller, air gap intake) rated at 430 HP and 3.73 gears. I love the trans and the driveability. I used OEM pedals and clutch linkage. The floor required minor tunnel mods. I ended up raising the tunnel about one inch in the center. It is unnoticeable with the carpet installed. With a 275/60/15 tire, I can cruise 75 mph at 2200 RPM. I put 2000 miles on it during Power Tour with no complaints.
 
#27 ·
I haven't heard anyone here mention the Richmond 5-speed OD and 6-speed...

The Richmond 5-speed (and 6-speed) will be almost a direct swap for the Muncie: same overall length means using the same driveshaft (may need a different slip yoke depending on the model/ output size/splines), same basic shifter location (on the side), bolts to the stock bellhousing, and uses the stock clutch (but depends on the model and your current clutch, comes in both 10-spline and 26-spline configurations as the stock Muncies. And most important, IMO, NO tunnel mods ( I did use a BFH for the Long shift linkage heim joint).

IIRC, I may have slid my crossmember back on the frame a few inches (I think the front hole in the crossmember lined up with the rear factory hole in the frame).

You might even be able to find an older version (Doug Nash)…


I ended up swapping in a Richmond Road Race version in place of the Muncie. Easy job... But it was the non-OD version (1:1 5th). But I wanted to build a new rearend (the rearend belonged to my other Chevelle), so I built a 12-bolt with 2.73 gears and positraction… With the 3.04 first gear and 2.73 rears, it was similar launch to the factory M21/3.73 or M20/3.31 set-ups. Another bonus, IMO, is the 2.73s kept the driveshaft speed low. Even with OD, you may be spinning your driveshaft too fast for its design (or figure $$$ for a new driveshaft)...
 
#36 ·
I used the factory driveshaft in my 68 when I installed my TKO. I had it shortened to fit the new combo and I have yet to experience any vibrations at any speed. Granted the OEM shaft was in excellent condition and I took the time to check the driveline angles when I installed the transmission. Eventually I want to build a new driveshaft, but the OEM piece worked to get the car on the road for PowerTour.
 
#29 ·
Hey guys, so I took the ole girl out last night when I went to the gym and there's about 5 miles of straight between here and there. I ran it in 3rd (1:1) and the RPMs are higher than I estimated, its more like 2800 @ 60 mph. I checked a couple online calculators to make sure that was right, and it appears to be. The torque is right under your foot and fun, but that's just too much RPM for my taste. I guess I'll just save my pennies for a McLeod or Richmond, keep my eyes peeled for a nice used unit.
 
#30 ·
I installed a TKO600 in my 70SS last winter. For what your looking for I would never spend the money on T56. My TKO from Silver Sport went in with no tunnel mods, just had to tap the floor up a little around the shifter hole. Best thing I have done to the car. I have 3.73's and it is a joy to drive on the highway now. I came from an M0 and have ZERO regrets.
 
#31 ·
There is a mod that can be done to the case of the Tremec transmission that is supposed to make it able to be installed without having to cut the trans tunnel. There may even be info about the case modification on Silver Sports website. Probably can get better info about it from site members that have that done than you could from Silver Sport.
 
#37 ·
I have an M22 auburn gear trans with 3.73:1 rear, same tires you have.

Sometimes I wish I had overdrive, but, it sure is fun on the street.

My take on the 5 or 6 speeds is, shift, shift, shift, shift, shiftshiftshiftshsaeie[jaf'l;k AHHHH!

With a bunch of torque you don't need a bunch of gears.

If you want better gas mileage and cruise speeds, get a 6 cyll Nova. just sayin
 
  • Like
Reactions: the heckler
#38 ·
If you want better gas mileage and cruise speeds, get a 6 cyll Nova. just sayin
I hear ya and the probability of highway travel its relatively low, so I'm inclined to run the M20. I live in the NE, which means winter is 6 months long, I don't get to put a ton of miles on my car every year. Fuel economy is not at the top of my list by any means, it's the 2800 rpm just to cruise the two-lanes that's making me hesitant. The cheapest way to remedy would be to just swap out the rear gear set for something taller, something to make the 60mph more tolerable.

If I'd just hit the jackpot, I'd have the bank to sort out a plan and do everything front to back all at once and not have to revert a change I just made haha.
 
This is an older thread, you may not receive a response, and could be reviving an old thread. Please consider creating a new thread.
Top