over drive Muncie , anyone understand this?

65 SD L79 · Canadian Poncho Superstar!

over drive Muncie , anyone understand this?

cdnpont · Canadian Poncho Superstar!

Overdrive? It's still 1:1 in 4th. But with some quite low 1st to 2nd ratios offered, if that's what they consider overdrive.

Stock M20, 21, 22,

Prefectca · Poncho Master!

The ones that I have seen third gear becomes the overdrive. The shifter lever for third/fourth is then flipped to restore the normal shift pattern.

Paul

65Camino · Uber Guru

Similar to the old Doug Nash transmission that was around in the 70s. The ultra wide would be the ideal one.

cdnpont · Canadian Poncho Superstar!

Any more thoughts on this OD Muncie? I'd like to know what they mean by Overdrive Equivalent.

DonSSDD · Canadian Poncho Superstar!

I think they mean they can build you a 4 speed with an OD 4 th gear. The ones they have ready are not od.

cdnpont · Canadian Poncho Superstar!

I see 1:1 final. Where is the OD?

Prefectca · Poncho Master!

The overdrive gear was third gear. Fourth was still 1:1. I think this was about fifteen or more years ago. When companies such as Doug Nash started building overdrive street transmissions the trend changed. I didnt think anyone was still doing the Muncie conversions anymore.

Paul

LT1Caddy · Poncho Master!

A company in New York state started repopping parts a few years back. I think they got bought out by someone (Doug Nash, who got bought out?). They were building better center sections for the Muncie because the case would wear out before the innards.
They came to prominence in Vintage racing for Vettes and Camaros. The name slips my mind right now...

LT1Caddy · Poncho Master!

LT1Caddy wrote:
A company in New York state started repopping parts a few years back. I think they got bought out by someone (Doug Nash, who got bought out?). They were building better center sections for the Muncie because the case would wear out before the innards.
They came to prominence in Vintage racing for Vettes and Camaros. The name slips my mind right now...

It came to me... Autogear in Rochester. Gears were made in Italy. I heard they were better than OE, guys I raced with said they were super.

DonSSDD · Canadian Poncho Superstar!

www.gearvendors.com/hrgm4sm.html

poncho62 · Poncho Master!

From ad......."Fry your tires departing the stop light as if you are running 4.10 rear end gears"

I think what this guy is saying is that they have this Ultra Wide 1st gear. Then you can run a regular rear gear and it will act like a 4.10 gear.

/download.spark?ID=2439648&aBID=118110

65Camino · Uber Guru

If you look at first gear of the standard unit there is a difference of .785. If you add that to your normal, say2.73-3.08 you now have a 3.515 to 3.865. While still keeping the final drive the same.

Similar to what happens when you install a 700r4 with its 3.059 first gear.

unruhjonny · Guru

I'm guessing this ebay listing was made when an overdrive set was available;
That set essentially flipped third and fourth (fourth was 1:1; third was something like 0.8~0.7:1)

That was an overdrive Muncie.

The listing is not.

I have wondered out loud as to why somoene doesn't step up to offer an alternate overdriven gear set - that gear set was quite popular, and sold out quick, but I am told after the fact that there were some issues with it (I am unclear on the issues).

I can't help but think that a gear set more like a car three speed with an overdrive would be a hit.

2.42/1.42/1.00/0.72

65Camino · Uber Guru

That would seem ideal. There is no need for 8 or 10 speed transmissions.

unruhjonny · Guru

yeah, the prevailing logic on drivelines has changed somewhat in the last fifty years;
I believe that fifty years ago a smaller gear spread was ideal - especially with lower horsepower engines - which is why an M20 was such a popular upgrade from a conventional (at the time) three speed;
This was even more amplified when a close ratio M21/M22 gearbox was set infront of a lower gear set.

These days the gear spreads are quite wide compared to what was the norm from fifty years ago.
The five speed in my Cobalt is a super wide where it's essentially a four speed with an additional overdrive gear - ditto on our Cailber - which is a super wide four speed with two additional overdriven gears.

Not many people realize that these days the first gear ratio is 3.xx while the normal first gear ratio from fifty to fourty years ago was 2.4x ~ 2.5x;
That nearly makes second gear in a newer transmission comparable to the conventional first gear from an older close ratio four speed transmission.

Looking at just the first four gears in these two cars I previously mentioned, it hopefully is plain to see why I was trying to draw comparison to four speeds and point out gear ratio spreads:

2008.5-2010 Cobalt SS (5 speed SAAB; F35)
- ratio 1st gear: 3.38:1
- ratio 2nd gear: 1.76:1
- ratio 3rd gear: 1.18:1
- ratio 4th gear: 0.89:1

2007.5-2009 Caliber SRT4 (6 speed Getrag; GF DMT-6)
- ratio 1st gear: 3.23:1
- ratio 2nd gear: 1.952:1
- ratio 3rd gear: 1.321:1
- ratio 4th gear: 0.971:1

Taking the best of both worlds to me would be a conventional (from fifty years ago) first gear ratio, and them making third a 1:1, and overdriving fourth.

My only qualm with the (discontinued) M21Y "marriage saver" gear set was the choice of first gear;
- ratio 1st gear: 2.20:1
- ratio 2nd gear: 1.51:1
- ratio 3rd gear: 1.00:1
- ratio 4th gear: 0.86:1