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Air-cooled Borg Warner auto in 1958-1960 Americans

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tomj View Drop Down
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Post Options Post Options   Thanks (0) Thanks(0)   Quote tomj Quote  Post ReplyReply Direct Link To This Post Topic: Air-cooled Borg Warner auto in 1958-1960 Americans
    Posted: Oct/17/2021 at 10:09pm
My 1960 American two-door wagon was originally a flathead/automatic car, the trans an M8, the iron auto also used behind V8s. In 1989 a very competent shop swapped in a 1962 OHV engine and aluminum M35 transmission. It hadn't run in years when I got it. 

The engine was ruined (.060 over and pitted #6 cyl) so I installed a rebuilt 1965 195.6 OHV and had the 1962 M35 rebuilt, as it is one of the few years that uses the throttle cable and not unobtanium vacuum modulators.

Because these were flathead cars the exhaust is on the passenger side, and runs the length of the car on that side.

The OHV has exhaust on the driver's side, but the brake master cylinder and parking setup requires that the exhaust cross over from left to right, then follow the flathead car's exhaust route...


Its all worked out fine until I set out on a long trip. The transmission got hotter and hotter (I'd installed an Autometer temp gauge, sensor screwed into the pressure test port), eventually reaching 250 F indicated [later at home my Fluke IR Thermometer said it was actually 240F]. I hobbled home, stopping six times for cooloff.

It was weird though; the trans behaved perfectly, just hot. I did some driving tests. I have a nice test route, the Glendale Freeway, about 10 miles of a 5% grade, up and back. Warmed it up on a separate fixed drive, I bombed it upgrade, 65 mph, near WOT for this car (5 in Hg), noted temperature (250), turned around, "coasted" 50 - 55 mph, light throttle (15 in Hg). It did not cool off. THat's just odd.

Pulled home, got under the car with the IR thermo meter. Noticed that the exhaust crossover (below) runs right below, 1/2" behind the crossmember -- and cooking the transmission. It was 300 F down there, heated by the exhaust!


So I wrapped the entire exhaust from drop down from the manifold to behind the trans with aluminum foil folded twice (four layers), spiral wrapped around the pipe, and a wrap of fiberglass cloth strip to retain it. Stainless wire tied downs every few inches. The dropped portion (manifold flange down) I wrapped with thin aluminum sheet (24ga?) and hose clamped at the bottom, since that side is directly in line with one of the two cooling air inlets in the bellhousing.


I repeated my test drive (8 mile warmup, then 10 miles of Glendale Fwy, 65 up/50 down) and at home, the same spot in the oil pan was 178F! That's a 60F temperature drop. 180 - 200 F is fine, 230F the fluid starts making varnish.


Today I dropped the pan (it was seeping) to inspect, changed the fluid (it might have been OK but oil's cheaper than transmissions). Tomorrow I'll test again.

If it holds, the lesson is that the air-cooling is adequate, but just so. My swap can't be that rare, a "late model" engine and trans in the 58 to 60 chassis. Most people don't put temperature sensors in their transmissions. I learned to do that in the M35 I had in my '63 Classic. 

Maybe also no one takes long trips in these things. It's been on the road a month without issue. I think you have to build up a lot of heat under the car to block transmission cooling, but it happens.

If this holds, I suspect it will, I'll order real exhaust wrap (though aluminum foil is a better insulator than most of the expensive stuff, it's just not rugged), probably put it over another roll of foil, and get more, thinner, sheet aluminum and make less-crappy shields.





1960 Rambler Super two-door wagon, OHV auto
1961 Roadster American, 195.6 OHV, T5
http://www.ramblerLore.com

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tomj View Drop Down
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Post Options Post Options   Thanks (0) Thanks(0)   Quote tomj Quote  Post ReplyReply Direct Link To This Post Posted: Oct/17/2021 at 10:15pm
BTW, the AMC owners manual says that transmission fluid shoudl be changed every 10,000 miles. WHere did this idea of "never need to change transmission fluid" come from? I remember "knowing" that. I'm sure I jusr believed what someone told me long ago. All that crazy talk of changing fluid causing problems. I know it's nonsense, and for a long time.

Back when I put the 1965 M35 in my 63 Classic, a small trans in a medium car (with a 232 in front), the brain-surgeon at B & E Transmissions in San Francisco that first rebuilt it said it needed fluid/adjustments every two years. I did that every 2 - 4. I then put 350,000 on that transmission, with one (two?) full teardowns over 20 years.

I'm gonna stick to the factory recommendation -- fluid change/adjust every 10K.

1960 Rambler Super two-door wagon, OHV auto
1961 Roadster American, 195.6 OHV, T5
http://www.ramblerLore.com

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Post Options Post Options   Thanks (0) Thanks(0)   Quote farna Quote  Post ReplyReply Direct Link To This Post Posted: Oct/21/2021 at 7:18am
 I change the trans fluid when it starts getting dark, but newer materials wear less and newer tech fluid (especially synthetic) lasts a lot longer. I still don't care for the "never needs changing" late model ideas. Maybe that's because the car engines last longer and they would really like the trans to fail around 200K miles? Hmmm... that's a good service life though, so if it lasted that long without a change is it really a failure?

My father in law was given our 2006 Equinox when his truck died a few years ago. 91 now, doesn't drive much but still does. About a year ago it stopped shifting into OD. It has a trans with a plug, no dip stick or easy way to add fluid. I told him to take it to a local shop and have them service the trans, fluid/filter change and adjust. They asked him how much he drove it after a test drive. When he said mainly around town they told him not to waste any money on it. It would be fine to drive around as is. I still think it may just be low on fluid, but kudos to them for not taking advantage of an old man!! I may take it over and have it done anyway, but not in a hurry to do so. He doesn't drive as much, and won't be much longer.
Frank Swygert
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Post Options Post Options   Thanks (0) Thanks(0)   Quote Ken Doyle Quote  Post ReplyReply Direct Link To This Post Posted: Oct/21/2021 at 9:45am
The Rambler service manuals in the mid-1960s state that the transmission fluid should only be changed at time of overhaul, but in my experience that is a very bad idea.  
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Post Options Post Options   Thanks (0) Thanks(0)   Quote tomj Quote  Post ReplyReply Direct Link To This Post Posted: Oct/21/2021 at 8:59pm
Interesting. Earlier owners manuals say 10K. Odd.

I'm in Tucson now. Car ran fine, transmission got warm climbing mountains, my temp sensor is measuring CASE temperature not fluid, case rose to 230, but my hand-held Fluke IR thermo pointed at a spot on the pan said 200 after a climb, so I'm calling it good.

I head to Santa Fe Sunday or Monday, then home to LA.

It is not a fast car! lol but at least the transmission is happy.

1960 Rambler Super two-door wagon, OHV auto
1961 Roadster American, 195.6 OHV, T5
http://www.ramblerLore.com

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