[Faustmill]

67 GTO with Muncie 4 speed and 3:55 rear.
I am turning 4000 rpm at 70 mph and 3500 rpm at 65 mph. These rpms are just too high for me on longer highway cruises. I think the car would be lot more comfortable at, say, 2500 rpm at 70 mph. Is there any transmission bolt-on gear box that would give me a high/low range and still allow me to keep the stock Muncie 4 speed? Thanks.

[richardk]

http://www.gearvendors.com/

[android 211]

Autogear sells a 'M-22Z' Rockcrusher which is a M-22 with a lower low gear set. 1st is available with 2.97:1 I believe. You swap that in for your M-21 and exchange your 3.55s for a cheap 2.73 rear axle assembly and you get the same off the line launch and lower highway rpm. No new driveshaft or cutting the floor. There will be more drop in rpm between shifts. $2200 before shipping.

[tom s]

There was a gear set made in Italy for muncies with a .85 4th gear.Only rub was a 2.20 first avail in it.I had one in my 69 bird with a 366 RAV short deck engine.Was very good in it with a 3.90 in the back.Dont think it would be great in a GTO weight car unless it had some cubes like a 455.Tom

["QUICK-SILVER"]

I'ld like to have one of these.

http://www.richmondgear.com/index.ph...t-5-speed-w-od

[Bill Hanlon]

Originally Posted by Faustmill

67 GTO with Muncie 4 speed and 3:55 rear.
I am turning 4000 rpm at 70 mph and 3500 rpm at 65 mph.

If you are turning 3500 rpm at 65 mph you should be running 74 mph at 4000 unless you have a bunch of clutch slip. Just curious, what is the diameter of your rear tires?

["QUICK-SILVER"]

Originally Posted by Bill Hanlon

If you are turning 3500 rpm at 65 mph you should be running 74 mph at 4000 unless you have a bunch of clutch slip. Just curious, what is the diameter of your rear tires?

Yes, I agree, something ain't right there.

With a 27" tire, I come up with 79mph at 3,500rpm
----------------
27" tire, 4.10 gear, 3,500rpm would put you right at 68mph

[KJL]

Have one in my 70 GTO with 3.90 gears and it works great. Just have to get used to the ratio changes. Second to forth is steep an third to forth is shallow. Had a m22 with 3.55 gears and a 71 400 (low compression) and it was not a problem with the 2.2 first gear. If you have a cammed 400 it may be a different story.

[Faustmill]

I knew someone would raise this issue. The rear tires are 26.1". So with a 3:55 rear, the calculator says 70 mph would be 3200 rpm (not 4000 that I am turning). These are rebuilt factory gauges (tach and speedometer), not aftermarket. The clutch does not feel like it is slipping. So I do not know how to explain this but you raise a good point. All I can say is that I have driven the car for 11,000 miles over the last 8 years and the tach says 4000 when the speedo says 70. Thanks to everyone for the thoughtful comments and suggestions.

[tom s]

If you have a smart phone,put in the wake app.Shows actual speed in MPH,no guessing.Tom

[Bill Hanlon]

Before you worry about changing things I think you should get an accurate base line. Either your speedometer, your tach or both are incorrect.

Beg, borrow or steal a GPS unit. Set it to display MPH and take it out on a highway without a lot of traffic. Run the car at 60 MPH as displayed on the GPS and record what the speedometer says. Do the same at 70 as indicated on the GPS and a few other points, say 40 and 50.

[goa484]

Originally Posted by tom s

If you have a smart phone,put in the wake app.Shows actual speed in MPH,no guessing.Tom

Tom,
What company makes that app? I searched for it and couldnt find it.
Brad

["QUICK-SILVER"]

Originally Posted by goa484

Tom,
What company makes that app? I searched for it and couldnt find it.
Brad

Here's some...

https://play.google.com/store/apps/d...es.speedometer

https://itunes.apple.com/us/app/spee...286577228?mt=8

[Don 79 TA]

why not swap in a TKO box
not sure how much floor massaging is needed for your app, check with that first

[Scarebird]

Originally Posted by android 211

Autogear sells a 'M-22Z' Rockcrusher which is a M-22 with a lower low gear set. 1st is available with 2.97:1 I believe. You swap that in for your M-21 and exchange your 3.55s for a cheap 2.73 rear axle assembly and you get the same off the line launch and lower highway rpm. No new driveshaft or cutting the floor. There will be more drop in rpm between shifts. $2200 before shipping.

I have a M22Z, but would disagree on the 2.73's. I have 2.93's and were I to do ti again would run 3.08's. This with a KRE headed 440.

[Skip Fix]

There was also a company that made an OD for the Nash/Richmond 5 speeds instead of 5th being 1:1.

[frbformula]

Im planning on running a M23z muncie from midwest muncie. That coupled with a 3.00 rear gear (Ford 9in) will put 1st, 2nd, 3rd final ratios very close to my current Th400 with 3.73 gears. Then the 1:1 4th gear in the trans will act as some what as an over drive. For me that is the best compromise for me. I want the feel of an original 4 speed but with a decent highway gear.

[AdamIsAdam]

Originally Posted by richardk

http://www.gearvendors.com/

Very interesting reading. My only issue is my current setup is the worst of all worlds. M21 with 3.42 ain't great for routine launches or low speed cruising. And while 3.42 isn't horrible I the highway, I'm not comfortable cruising over 3,000 for extended periods, meaning I'm staying below 65mph with 26" tires. Some day maybe I'll change everything. Lol

So thanks for this info. Good reading

[lfdsteve]

Dropped my m20 for a tko 5 speed last year after a 4 hr round trip to Woodward at 3000+rpm.
Easy install ( in a FB anyway) and flawless. Prpbs $3600 total w hydraulic clutch and twin disc upgrades. Just keep in mind I don't race so unsure in a street strip application. I have heard both good and bad on longevity if racing.
Steve

[AdamIsAdam]

Originally Posted by lfdsteve

Dropped my m20 for a tko 5 speed last year after a 4 hr round trip to Woodward at 3000+rpm.
Easy install ( in a FB anyway) and flawless. Prpbs $3600 total w hydraulic clutch and twin disc upgrades. Just keep in mind I don't race so unsure in a street strip application. I have heard both good and bad on longevity if racing.
Steve

I would think that would be the better way to go for a set up like mine as long as that tranny can survive being behind 550+ foot-pounds of torque. 99+ percent street use but I do have a heavy foot. But I've heard it's a rough install.