Is the 3 speed as durable as the M-20?
 

A friend may have one of those dearborn (?) 3 speed trans that he says was pulled from an old 400 lemans.
I have not seen it but he wants $100.

I have a 71 GTO, with a fresh 464, 6x-4, (9.5:1) Melling 041 clone (spc-8), Rhoads lifters, 1.5 rockers, RA manifolds with X pipe, Muncie M-20, and a 3.73 12 bolt with a yukon posi.

I know folks have blown muncies with much smaller engines, so i'm guessing that this is the weak link in my setup?
I dont race the car but I am tempted to try a few passes.
There is nothing wrong with my muncie; I'm very happy with it. I never stray far from home with my car and so an overdrive trans doesnt interest me.
I was just wondering what the scoop is with the 3 speed and if it's worth buying and rebuilding for a quick fix backup?

Muncie also made a 3 speed, which was the base transmission in 1970.

No experience with either 3 speed...seem to recall reading that the earlier 3 speeds were Dearborn's because Muncie could not make enough, then by 70 they were able to produce sufficient quantity. Memory fuzzy on this so happy to be corrected...

One of my street racing buddies in the 70s liked 3 speeds for their ratios over a 3 speed. He had a 455 in a 65 Chevelle! Hammered on them hard.

The Dearborn 3 speed is a heavy duty beast. Stronger than a Muncie. Need a different yoke for it.

The Ford 3 speed is very strong and was used in Ford commercial vans for many years.
In the 1964-1968 timeframe you could get a Ford 3 speed trans instead of the GM trans in the A-Body vehicles. Some GM (Pontiac Bellhousings have both bolt patterns.
The bellhousings are more common than you would think.

If you just wanted a durable (strong) trans with 3 speeds - much like a Turbo 350 auto trans then the Ford piece is the way to go if you like rowing gears.
I have blown up Muncie Trans which is why I run a Doug Nash 5 speed trans today.

Tom V.

Never heard of one blowing up. It is a cast iron trans, top loader, just like it's bigger brother the Ford 4-speed top loader. It is a HD tranny, fully synchronized, and smooth.

I have had a couple of these and like them. The only downside is that they are 3-speeds. Taking off from a stop and rowing through the gears works great when racing from a stop. But, get challenged on the street where you are at a speed where you can't drop a gear to put a kick into the engine, and the other car may pull away even if you have the bigger engine - that's my only negative comment about them.

For $100.00, I would not pass on it. With a good torquey engine, probably a good choice. Try it, or keep it as a back-up.

Does it include the yoke and shifter?

My '68 GTO came new with the M-13 . IN '68 that meant a Dearborn Beast. Vs a whimsy saginsaw..this 3 speed Is the heavy duty 3 speed. And it's heavy.. That trans sat behind a Factory stock 2bbl 400.. basically the most basic GTO, but it had hideaways..

If it were mine, and you just want to have a little fun at the strip and make a few passes like you mentioned, I'd just run the M-20 and forget about it.

Since you're just wanting to "try" a few passes I sense you aren't serious about sticky tires, 4000 rpm clutch dumps and 60 foot times. With street tires I wouldn't worry about it.

There have been dozens of Muncies, I have personally seen, leave their parts on the street, or limped off to the side of the road with street tires on GTOs. I've never seen/heard of one of the ford three speeds ever break, but in shear numbers the Muncies outnumbered the ford by probably 50 to 1.

All you have to do is lift one of the ford transmissions up and compare how much heavier they are compared to a Muncie, even missing the parts for an extra gear, they out weigh a Muncie by a noticeable margin. If that doesn't convince you take the inspection cover off and compare the difference in size of the innards piece to piece. They also have the tougher case, being made out of iron, rather than aluminum, that the Muncies are made with.

When Pontiac came out with their 455 they also came out the following year (1971) with an M21 HD, which was touted to be nearly as strong as the fabled M22. The M21 HD was used until 1974, then GM used Borg Warner 4 speeds. I had one of the M21 HD transmissions in my 1973 Grand Am, and I was never able to break it, I just changed the car over to a T400, because I prefer the strength, over an OEM 4 speed. When the first clutch went south, out the 4 speed came. Since the car was a D/D the X wife wasn't that good at driving a stick anyway, it just simplified everything at the time.

Had I not seen the added strength in the T400 transmissions over the Muncies, and went with the T400, my next logical step would have been to outfit my GTOs with a ford top loader 4 speed. Since most Pontiac bellhousings were also drilled for the ford bolt pattern, it would have been a fairly easy swap. They are head and shoulders tougher than any Muncie made. They also take 2 people to lift one up laying on your back while changing clutches, so there is a weight penalty that is probably equal to a T400.

:focus:

John Sawruk was a drivetrain engineer at GM during the muscular years and one of his jobs was durability testing. That consisted of nonstop full throttle power shift passes until a failure occurred. When the 455 came out in 1970 he said the Dearborn 3 speed was the only trans they couldn’t break. The Muncie 4 speeds couldn’t handle the big torque engines which led to the Super T10 taking over as the 4 speed of choice for GM.
I’ve heard they had a tendency for the Dearborn to hang up between gears but that may have been more of a shifter issue.

Our 70 GTO had the Dearborn 3-speed; great ratios, and more fun than a 4-speed.

It would certainly get caught in 2- gear and lock-up.
usually while hitting the brakes while approaching a TollBooth. The Shifter needed Cal'd and tightened to prevent the lockups.

In talking to Arnie Beswick many times about racing in the "old days" he mentioned that the 3 speed manuals were stronger and more reliable than the 4 speeds of the day. So I assume he was talking about the Dearborn HD 3-speed VS the BW 1st generation T10 4-speed. Also fewer gear changes with the correct rear gearing could be quicker as well. Aluminum case Muncies, while light and super easy to repair, are not up to the kind of power we can easily make today and the sticky street tires we have either. They were borderline in the 60's with around 400 HP 450 lbs. of torque and the rock hard street tires of the time.

X4 or 5 that the Dearborn HD 3 speed is a stronger gearbox than the Muncie. By a bunch, I suspect.

The Saginaw had no synchro on 1st gear. Ypu had to "double clutch" or shift to second before you put it in first when stopped. When you're moving, there was no putting the trans in first. I had the Saginaw in my 1965 Lemans. It did not hold up to power shifting even with my 326 2 Bbl motor. I had mine rebuilt once in the 2 years I owned it. 2nd and 3rd gear synchros went bad and the trans would "snick" on the upshifts and downshifts.

I had a '64 Ford Galaxie w. the Dearborn trans, which had a synchro first gear, but I can't speak for durability other than having no issues behind a wimpy 2 Bbl 390.

RIP JOHN and MACK. You could always take his (and Mack McKellar's) info to the bank.

IF you installed a Proper Hurst 3 Speed Shifter on that 3 speed "Top Loader"
trans You rarely ever had shifting issues.

Tom V.

The Ford 3 speeds were tough, but they were put behind 240, 300 six cylinders and 289s, 292s and 352s, none of which were powerhouses.

There were 133 different versions of the TopLoader 3 & 4 speeds for different applications. GM received the 'RAT' 3 speed version which was primarily used for the higher horsepower cars, trucks, and Broncos.

This 3 speed transmission was updated to a four speed O'Drive in the late 70s (RUG Version) used behind small Ford V-8s and sixes. Not suitable for high horsepower
Chevrolet used the Dearborn in their 1/2 ton trucks during the mid 70s.
Rights to the design were sold to Tremac who used it in Jeeps.
The T5 is probably a direct descendent.

Yes, I know. My uncle built many Ford based circle track cars with the top loader, and he managed to destroy a few behind 427 FEs.
The overdrive one in pickups was more for70s economy concerns.

Many years ago I used one in my 1961 Chevy PU behind a mildly built 455 Pontiac engine. Used it as a TRUCK plus drag raced it once in awhile. Never had a problem. You have the fun of shifting with only 3/4's the work. Seriously use a good shifter and you should enjoy it.