Anyone actually running a late model automatic behind a flat six?

[chop]

I'm running a 904 behind my 230, haven't got it running yet but I can't wait to see how it does,

 

[greg g]

You gonna have room on your drive shaft for 2 U joints?????  what else os going to be mounted to that nice frame?

[bbbbbb99]

I had a 56 Plymouth that I saved the 230 and the trans adapter from. The car had come with a powerflight. It is my understanding that the bolt pattern is the same as a  torqueflight. Anyone know if this is correct?

[wayfarer]

I had a 56 Plymouth that I saved the 230 and the trans adapter from. The car had come with a powerflight. It is my understanding that the bolt pattern is the same as a  torqueflight. Anyone know if this is correct?

While the bolt pattern may be the same as pre-62 TF, the starter mounting plate is not the same as that which is required for the TF.

[Tim Keith]

I think the 200R4 might be more efficient than most of the rear drive transmission and about as compact as the 904.   The 200R4 will often fit into a tight space that other O/D auto transmissions require floorpan mods. 

 

The GM Powerglide has low parasitic losses but won't get good economy because of the lack of gears.  I think the 200R4 has a more efficienct design than the 700R4 or the Mopar 518, but size and light weight are advantages of the 200R4.  The 200R4 has good support and reliability shouldn't be a problem, but would cost more than the 904.

 

A 904 would be a good choice, but as it requires as adaptor from Wilcap or another source,I'd probably look at the 200R4 and get the over drive as a bonus.  I think these motors benefit from an O/D.

[William Davey]

Not exactly on-topic, but this site  http://www.transmissioncenter.net/ has some very interesting info on how to make a 518 OD with lock up transmission work with simple pressure/vacuum switches.  Their mission is to make the 518 as common as the GM transmission conversions. 

[Frank Elder]

I think the 200R4 might be more efficient than most of the rear drive transmission and about as compact as the 904.   The 200R4 will often fit into a tight space that other O/D auto transmissions require floorpan mods. 

 

The GM Powerglide has low parasitic losses but won't get good economy because of the lack of gears.  I think the 200R4 has a more efficienct design than the 700R4 or the Mopar 518, but size and light weight are advantages of the 200R4.  The 200R4 has good support and reliability shouldn't be a problem, but would cost more than the 904.

 

A 904 would be a good choice, but as it requires as adaptor from Wilcap or another source,I'd probably look at the 200R4 and get the over drive as a bonus.  I think these motors benefit from an O/D.

You realize the person who posted just before you sells the 904 adapter.....Wayfarer.....lol.

[wayfarer]

 

 

A 904 would be a good choice, but as it requires as adaptor from Wilcap or another source,I'd probably look at the 200R4 and get the over drive as a bonus.  I think these motors benefit from an O/D.

 

...and you think that the shiverlay trans does not require an adapter...??

 

...and a clarification....

Pat McGuire (Wilcap) does not sell the TF adapter, I do.   Pat sells the gm adapter.

 

 

(Frank, thanks for the nod!)

[Lumpy]

The 904 is plenty strong, I've had one behind the (very "healthy") 360 in my Dart forever. People always seem perplexed as to why I use a 904 instead of a 727. As long as I was not drag racing on a regular basis, I wouldn't use a 727 behind a 318 or 360, just for the reason of getting some "free" horsepower with the 904....so I'm sure it's plenty of tranny behind a flathead six. The 727 would indeed just take more power to run.

 

With any auto trans, a cooler and deep pan is always a good idea.

 

ken.

[40desoto]

If anyone needs a 727 straight six adapter I have one.  Also have a 727 tranny.  Condition unknown.

[knuckleharley]

...If you do decide to go with a 904, I recommend going to a deeper pan and running a nice trans cooler with plenty of air flow. The killer of any automatic transmission is heat. The extra fluid and a functional trans cooler will keep your fluid from getting too hot and keep the insides of your trans happy. 

I am a big fan of synthetic ATF,also. I  run it in the trans,transfer case, and differentials in my 4X4 diesel pu,and will be running it in everything I run from now on.

[Lumpy]

Synthetic is good, I'm also a fan. But I usually run Ford type F, (in Chrysler transmissions) improves the shifts a bit. Back in my drag racing days we would run quite a bit of straight 30wt motor oil...25 to 50% I would guess, in our 904s and 727s. That (the much heavier motor oil) would rob some power of course, but also made for good firm shifts.

 

That adapter is interesting, and of course anywhere a 727 bolts up, so will a 904. Or...is that adapter for a big block bell housing? I guess if it fits the big block tranny, then it wouldn't work with a 904. ?

 

Another thing I thought of, if someone was going to run a 904 or 727 behind a flat six, would be to look at different stall speed converters and figure out which one/speed would optimize the tranny for a flat six. Something higher than stock, but not too high, might get the car off the line better. Or would lower be better with all the low-end torque? Just a thought.

 

ken

[austinsailor]

The talk of losing 50 hp with the automatic is interesting. I had a 55 Plymouth years ago with a powerflite. It's listed as 118 HP. The 2 speed automatic wasn't as good as a 3 speed standard, but I could nearly keep up with them. It certainly didn't take nearly half the power.

 

I can't imagine that there is that much difference in gear mass between them, as there are quite a number of gears and shafts in the standard.  They are always turning, and once they are turning, it's a wash. Besides, the ATF is much lighter and should have less resistance than heavier 90 weight. Except for the inefficiencies - slippage - of the torque converter, and the lack of a 3ed gear to take advantage of staying in the power curve better, I can't understand why it would be less efficient.

 

I've read reports and tests of modern automatics, and many get better mileage and performance than the standards in the same setup.

 

But then, you might ask, why do I have standards in everything I have, new or old?  Some things just can't be explained with logic!

 

Gene

[Merle Coggins]

I believe where you have a power loss in an automatic trans is through the torque convertor. Most torque convertors are only around 85% efficient. If you have a lockup converter that eliminates that power loss.

Also, assigning a HP figure to the power loss is inaccurate. That would depend on the available HP to begin with. It should be a percentage figure instead.

[Frank Elder]

Less loss of power through an automatic than a fluid drive.....I've had both and much prefer the automatic.

[YukonJack]

HI all, I am running a 700r4 behind my flat 6. Its a 47 Plymouth business coupe. I used the Wilcap converter and have been driving it for about 1000 miles or so now. I also put an Explorer rear axle with disc brakes and 3.56 ratio. It tachs about 2200 at 65mph. It definitely doesnt have the torque it used to with the 3sp but i can drive on the freeway easily now. I have no regrets other than the fact that i could have put in a v8 w auto trans easier. I havent installed the lockup kit yet but i have the TCi kit to put in.

Do you have any pictures of how you hooked up the tv cable?

[martybose]

I believe where you have a power loss in an automatic trans is through the torque convertor. Most torque convertors are only around 85% efficient. If you have a lockup converter that eliminates that power loss.

Also, assigning a HP figure to the power loss is inaccurate. That would depend on the available HP to begin with. It should be a percentage figure instead.

Don't forget that you are also driving a fairly high pressure hydraulic pump to accomplish all of the automatic shifting.  That takes a few horsepower.

 

Marty

[wayfarer]

 

Also, assigning a HP figure to the power loss is inaccurate. That would depend on the available HP to begin with. It should be a percentage figure instead.

 

...really?  So, if a TF is hooked up to a 1cyl Briggs and Stratton it would some how use less power than when hooked up to a 500 ci B engine? The estimated hp losses are just that, estimates...until someone finds some dyno reports... but the internal losses are there. HP is required to move fluid, turn gears and it readily shows up as heat.

[Robert Horne]

http://etereman.com/blog/automatic-transmission-2/dyno-testing-a-re-manufactured-automatic-transmission-and-why-its-important/

I had never seen any info on transmission dyno testing before.

Found this site this morning.

[Plymouthy Adams]

I posted some information earlier on this very thread for those coming in at the very end of the discussion that may be of benefit...see post 14...and do not underestimate the AT as what may be robbed to run in horsepower is applied back in form of multiplied torque...look at how many 727 AT's are connected to the /6 from ma Mopar over the years...I recall well the very smooth performance and smooth ride of my 76 Dodge D100 short bed camper special from the factory with /6, 727, 3.55 rear gear and 43 gallons of gas on board and secondary leaf springs.  I have carried loads on that truck that would kick in the secondary springs and actually make one concerned that the tires would pop just sitting there..

[traveller816]

HI all, I am running a 700r4 behind my flat 6. Its a 47 Plymouth business coupe. I used the Wilcap converter and have been driving it for about 1000 miles or so now. I also put an Explorer rear axle with disc brakes and 3.56 ratio. It tachs about 2200 at 65mph. It definitely doesnt have the torque it used to with the 3sp but i can drive on the freeway easily now. I have no regrets other than the fact that i could have put in a v8 w auto trans easier. I havent installed the lockup kit yet but i have the TCi kit to put in.

Can I ask what size and output your flathead is? I'm thinking of going down the 700R4 route myself and am in the midst of researching before ordering my adaptor. I've got a 251 flathead 6 and I'm thinking of ditching my fluid drive and 3 speed. I think the standard axle ratio for my car is a 3.91 so I'm trying to get an idea of how the conversion might end up.

[wayfarer]

Can I ask what size and output your flathead is? I'm thinking of going down the 700R4 route myself and am in the midst of researching before ordering my adaptor. I've got a 251 flathead 6 and I'm thinking of ditching my fluid drive and 3 speed. I think the standard axle ratio for my car is a 3.91 so I'm trying to get an idea of how the conversion might end up.

 

Bringing this thread back to ask traveller816 how his search/swap project is going.

[greg g]

I had a ride in John Burke's car. It was a cut down model A coupe (roof delete) on a home made frame. Couldn't have weighed more than 2000 pounds. Had a dual carb'd 251 DeSoto backed up by a GM 350 auto. Not sure what rear end he had in it but on the gravel roads through the corn fields of Eastern Nebraska it gave me all the ride I will ever need.

[Don Coatney]

John Burke's car.