Automatic trans coupled to flat head

[greg g]

Might want to also check out the ALLPAR site. Use the search function for transmissions it will return a bunch of stuff on MOPAR automatic transmissions and all there permutations.

[Andydodge]

Oldaddy.......is that correct that the RV 727 Torquflites had a drum brake on them?.........any idea what yrs?......I've learnt something today......thanks, andyd

[Young Ed]

If you want to run your original parking brake and rear end, look for a 727 from an RV. They had a drum brake mounted on the tailshaft where the earlier Mopars had an open brake. They work the same and you can keep your original brake, and rear end. They also have the flat plate mount for the u-joint so your original drive shaft setup will work, but you will probably have to shorten it.

How would an automatic work out with the ratio of the original rear end?

[grey beard]

Autmatic trans-equipped vehicles typically used a lower final drive ratio, because of the torque convertor coupling, so they should fit into our older, slower stuff just like a hand in a glove. This idea sorta' tickles me. Now if I can just find a later automatic with overdive, I'd have the best of both worlds . . .

[kencombs]

"He is recommending a 904 trans for it's final drive ratio.He makes an adapter to the six as you know."

I don't understand his reasoning as all Non-overdrives, 727,904 and in fact all makes are 1-1 in third gear.

One of my first decisions in making my trans choice was to eliminate all non-overdrives. The overdrive makes highway driving much easier on the engine and the driver. As far as I know, the overdrive versions bolt up to the engine and converter just like the 904&727 so the adapter will still work.

This also allows you to use the same rear end if desired.

I will likely use a disk parking brake on the pinion yoke, or adapt later brakes to my original rear end. It is already converted to studs instead of bolts.

[Happyhewy]

"He is recommending a 904 trans for it's final drive ratio.He makes an adapter to the six as you know."

I don't understand his reasoning as all Non-overdrives, 727,904 and in fact all makes are 1-1 in third gear.

One of my first decisions in making my trans choice was to eliminate all non-overdrives. The overdrive makes highway driving much easier on the engine and the driver. As far as I know, the overdrive versions bolt up to the engine and converter just like the 904&727 so the adapter will still work.

This also allows you to use the same rear end if desired.

I will likely use a disk parking brake on the pinion yoke, or adapt later brakes to my original rear end. It is already converted to studs instead of bolts.

Went back and reread his message. The recommendation was 904,998,A500

The reference to ratio is the A500.

Is that an overdrive unit? edit "Further investigation it is an OD trans"

Edited September 9, 2009 by Happyhewy

[grey beard]

Spent half an hour talkig with Russ Fisher, of Fisher Trans, Fairfied, NJ. This guy is the real transmission guru - forty plus years in the business and he is a MoPar guy. Here's what he has to say on this issue:

The Torque Flight used behind six cylinders was an early cast iron version. It had a dedicated bell housing deign that stands alone from the later V-8 transmission. To his best knowledge, this is the only automatic configuration put together with a flathead - other than the special equipment like the airport tugs, etc.

This means that the only way whereby one could couple an overdrive automatic box to our flatheads would be by using a third party adaptor. For my money, if I must go this route, the gearbox will be a GM 700R4. This trans has a 30 percent overdrive that is very nice PLUS a very low first gear. Sorta' like the best of both worlds. What is needed here is the early non-electric version that does not require computer dedication, as the later units all do. Wish I knew more about the adaptors and what else is required.

Anyone who goes ahead with this idea, please let us konw how your progress goes.

Thanks

[kencombs]

The 700 is a tough trans allright, but I don't see any substantial difference with it and a 727 or it's overdrive derivative. And the 700 is a very inefficient user of power passed through it, I've read that it uses a lot more than other competitive designs, especially compared to it's smaller brother, the 200. The low gear is not a real advantage, and could be a disadvantage if you elect to keep the original rear end, which is also low geared.

It would be a real stump puller, but not very useful at the stoplight.

[bbbbbb99]

I've got an original flattie to auto adapter. I was under the assumption that any V8 torqueflight of any year would bolt right up. Charlie????

[Plymouthy Adams]

wrong...small block is one pattern...big block is another..

[wayfarer]

Time for an up-date from happyhewy.

Keep in mind the parasitic losses in some of these transmissions as mentioned by kencombs. I do not recommend using the 727/518 because of this.

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