[oldman66gto]

Being new to this forum, and quite a few years since working on classic vehicles, brings the above question.

I bought a '66 GTO, which has a 428, with a newly rebuilt Muncie 4-spd, and it has a 3:55 rear. And as you guys know, it turns significant "RPM's" at speed.

Is it very difficult to change over from the Muncie to the Tremec?
I've checked into pricing, and it's not cheap. Especially if I get all that they recommend in their quote. This is gonna be a challenge for a 78 yr old

Would the Muncie be a desirable transmission to sell? Price??

I look forward to the response and advice from Y'all, as there seems to be tremendous knowledge & experience in this forum.

Thanks.
Allan

[Scarebird]

It is not a task for amateurs. To be honest given your age I would assess how long you plan to drive it and how you drive it.

If just running down for ice cream I would leave well alone - 3.55's are within my limit for final gearing.

If you put 5,000 or more miles a year on it I would change.

[tom s]

I’m 80 and it is the single thing I have done to one of my pontiac.Have had them in 3 fiff cars.The new one I don’t think you have to cut the floors.Use you bellhousing,you pressure plate and put a 26 spline disc in.I would buy the aftermarket trans X member.You drive shaft will need to be shortened and a trans input yoke.You will need a shifter handle and the one from you trans.If you stay with you clutch linkage and bell and pressure plate it will save you a lot of money.Tom

[oldman66gto]

Called the guy doing the work ...could not stand it any longer!
9 days til I return home.

Car is all together! Trans shifts smoothly, clutch is great,and he said a pleasure to drive. His comment to me, "This is one of the nicest GTO's I've ever worked on"! WOW Made my head swell! Not really, but happy to hear.

He said the tri-power set up change over was a breeze, as Mike had sent everything he needed to do the swap! Man, I was ecstatic about that. Said it works amoothly, but can't go full throttle until after the 500 mile break-in, and fluid change on the transmission. Also the new "small" diameter distributor was a breeze to install. He's saying he thinks I will be impressed with the installation, as it all looks original, even to the "AC" fuel filter, & yellow throttle spring!

"Hi" fan on a/c fixed....a wire

When changing valve cover gaskets, he tells me that it has stamped rocker arms. Said that cylinder heads, rockers, and all look like new. His comment was that this car has had excellent care taken of it. Underside, underhood, inside & out! Don't mean to be bragging, am just so pleased that I bought such a nice car. As an aside, I just wish I could find out who did such a nice restoration. Car was purchased new, in Ashville NC, at the original Harry' Pontiac GMC, which is still in business and known locally as "Harry's on the Hill". The car seems to have spent its' entire life in the Morganton NC area! Enough rambling!

I am pleased that everything seems to have gone so well, with few little glitches, and am anxious to get back to Florida, and see it, but more importantly, drive it!

Happy New Year!

Allan

[donziboy]

Did the TKX transmission fit without modifications of any kind to the floor?

[oldman66gto]

Originally Posted by donziboy

Did the TKX transmission fit without modifications of any kind to the floor?

YES, The newer version from Silversport works fine. Even used the standard, with a slight relocation, but there weree existing bolt holes in the frame.

[george kujanski]

Rebuilt Muncies sell for the price range of around $1200 from what I have seen.

George

[Scarebird]

Tom, I was hoping you would chime in here - you are a superb example of a life lived well. Some age better than others - hence my hopefully non-judgemental comment on essentially being honest with one's goals and capabilities.

The sorta new TKX fits quite well in older stuff but not perfectly - trimming is required.

[b-man]

If you should decide to keep the Muncie 4-speed going to a little taller rear tire will take the edge off those 3.55 gears at highway speeds.

Going an inch or so taller would bring those 3.55s close to having swapped gears to a 3.36 or 3.31.

[krisr]

I just put 215/60's on my GTO and it turns 2400rpm at 60mph. I used to run 255/60 tires and it was less obviously, but it's not crazy rpm's. How low do you want the RPM? Mine is a 4 speed Muncie + 3.5 rear ratio.

[oldman66gto]

Originally Posted by oldman66gto

Being new to this forum, and quite a few years since working on classic vehicles, brings the above question.

I bought a '66 GTO, which has a 428, with a newly rebuilt Muncie 4-spd, and it has a 3:55 rear. And as you guys know, it turns significant "RPM's" at speed.

Is it very difficult to change over from the Muncie to the Tremec?
I've checked into pricing, and it's not cheap. Especially if I get all that they recommend in their quote. This is gonna be a challenge for a 78 yr old

Would the Muncie be a desirable transmission to sell? Price??

I look forward to the response and advice from Y'all, as there seems to be tremendous knowledge & experience in this forum.

Thanks.
Allan

As another option, what about changing the rear to a 3:36? Would having a new rear "set-up" and installed be less expensive than the Tremec swap?
Just trying to think about engine load when on the highway. I would like to take it from here in St. Augustine to maybe Gatlinburg. How hard it is that gonna be on the engine. Heck, I'm used to these new 6 spd & 8 spd "OD" transmission, and the engine turning 1600-1800 at 65 mph!

And another question regards value. I presume the Tremec would add a decent bit of value, whereas the 3:36 may reduce its' value & desirablity.
What's your opinions.

I'm not opposed to spending the money, but want to do whichever gives the best value, & will help the value most, when time comes to part with it. Which do you think a buyer would prefer?

It's a beautiful car, & in awesome condition, and I don't want to do something that would have a negative impact. If that makes sense!

Thanks again for your advice. This is a knowlegeable and wise group, and I appreciate the help.
Allan

[Scarebird]

Is this Muncie a M20 or 21?

[oldman66gto]

Originally Posted by Scarebird

Is this Muncie a M20 or 21?

LOL!! At my age it's getting harder to remember the numbers.
BUT, itis not the "close ratio" transmission. Is that the "M-20"?

Allan

PS: Today is a travel day, so I may not be able to get back on. And great replies, Y'all are making this ol man think!

[OCMDGTO]

3.55 to 3.36 will be hardly noticeable. 3.23 to 3.50 in my car was only a 150rpm difference

[geeteeohguy]

Originally Posted by OCMDGTO

3.55 to 3.36 will be hardly noticeable. 3.23 to 3.50 in my car was only a 150rpm difference

I swapped the 3.55 rear gear in my 4 speed '65 GTO for a set of 3.36 gears in 1990. My cruise speed went from 60 mph to 70 mph. To me, a big enough difference to be worth it.

For the OP: with the Muncie M-20 and the 428, I would source a 3.08 geared rear end and bolt it in and be done with it. Thousands cheaper than a 5 speed conversion, you get to keep your 4 speed and Hurst shifter, and the swap can be done in a day with no modifications other than changing the speedometer gear at the tailhousing.

[Gator67]

I run an M20 and 3.55 in my 67 GTO (462ci)...the car has been on many long trips over the years. In fact, a previous owner was in the Navy and drove it back and forth between California and Virginia several times. That said, interstate traffic seems to move a lot faster these days so I too am considering a 5-speed swap (TKX).

[tom s]

On change that I did in my 62 GP was to put a 3.42 first these ST-10 and a 2.68 in the back gave me what I wanted.EZ pull away from a stop sign and low RPM cruise on the highway.Would not be a good race change but for a solid cruise car it’s great.First car I did it in was a 63 421 GP so the 63 421 GP was a EZ choice.FWIW,Tom

[b-man]

If going to the trouble and expense of swapping rear end gears go at least to 3.23 and if highway driving is a priority then consider going to 3.08. This assumes a Muncie M20 with either the 2.52 (late) or 2.56 (early) first gear.

Keep in mind that in the city taking off in first with a 3.08 rear gear might involve slipping the clutch more than you’d like. Depending on how radical your cam is you might not want that 3.08 so help us out and let us know what cam you have or at least how it behaves.

You haven’t yet shared your rear tire size which is a very important part of the equation.

[Scarebird]

That would be great if it was a M20.

[oldman66gto]

Scarebird

Hi, Yes Sir, it is an M-20
I can post the case number, tail shaft, side case numbers if needed?