Fluid drive engine drag

[meadowbrook]

I was wondering how much drag the fluid drive in a 50 Dodge Meadowbroook should cause. When I don't press the clutch at idle, in gear, my engine goes from a 500 rpm idle to something like 350 rpm, and certainly does not feel happy. Could it be that the fluid drive fluid has changed in viscosity due to age (as far as I know, it's original) and should be changed?

[Don Coatney]

What does your shop manual recommend for idle speed?

[meadowbrook]

450 rpm

[Don Coatney]

Is that 450 RPM reading taken with the car in gear and the fluid drive engaged?

[meadowbrook]

The book says 450. No further details. My current setting is 500 in neutral, which drops to 350 in gear

[Tom Skinner]

Try 450 in gear. The Book will tell you (with rear Wheels Raised in Gear 8-12mph is good)

Its OK if its 500 + in Nuetral, When the Transmission Pressure is right (around 40lbs) it upshifts just fine, and downshifts just fine.

Tom

[meadowbrook]

I will try that, however, I have a manual trans. I do believe if I set it to 450 in gear, it will be like 750 in neutral.

[greg g]

adjust the idle speed in gear with the e brake on or wheels chocked till you feel it feels happy.

[DLK]

I was wondering how much drag the fluid drive in a 50 Dodge Meadowbroook should cause. When I don't press the clutch at idle, in gear, my engine goes from a 500 rpm idle to something like 350 rpm, and certainly does not feel happy. Could it be that the fluid drive fluid has changed in viscosity due to age (as far as I know, it's original) and should be changed?

With my Wayfarer with the same 3 speed - fluid drive setup I have always put in the clutch at stops and started out in second gear. It gives me acceptable acceleration and keeps my rpm's from dropping while stopped in gear.

[doctor dirt]

I do the same however a slight clutch adjustment and a 475-525 idle should help the stand still at lights. I've found the ISO 32 (home depot & napa by oredering) after searching at one time for 2 months but during my search settled on Kendalls 10W and it equates to the numbers that ambsol showed and ISO 32 offers!  (app. 7 qts.)

The drag I'm feeling right now coupled with the lack of clutch when backing up leads to an adjustment. I'm at a disadvantage waiting for an opening at a friends lift. I've offered the car to a few garage mechanics but they all pass on it (all young fellows). Hopefully this Sunday I can sneak on the lift and try some settings.

 

Good luck, I've had my Wayfarer for about 10 months now and sorted out a few simple things that are important such as the correct old style thermostate along with using the old style "green coolant" as opposed to the modern mixes.

This is a great place to gather info on both cosmetics and mechanics.  Doc.

[Lumpy]

I'm with Greg G on this one.

 

k.

[James_Douglas]

Perhaps the webmaster will post this in the tech section.  I have posted it before, but here it is again.  I adjust my car to idle at about 475-500 rpm in gear with the fluid coupling.  The various comments on fluid are all in various ways not correct.  Read below.

 

James

 

Technical Note on MOPAR Fluid Couplings
 (Fluid Torque Couplings are NOT covered by this Technical Note)
By James Douglas – San Francisco

 

 

Having run several types of oil in MOPAR “Fluid Couplings” over the years and heard many recommendations, I decided to see if I could approach the issue of what lubricant to use in one of MOPAR’s Fluid Couplings by a more scientific method.

 

As is well known, Chrysler instructed all owners to use “MOPAR Fluid Drive Fluid” only in their Fluid Couplings.  Problem is, MOPAR stopped making it decades ago.

 

My first stop was Chrysler Historical.  After a month of looking, I was told that they do not have any of the original engineering information as to the specifications of the fluid.

 

Then I headed off into internet land to hunt down anything I could find on the subject from ORIGINAL sources.  I managed to find an original Chrysler Question and Answer sheet from 1939 about fluid drive from Chrysler Engineering.  In it they stated:

 

“…The proper fluid is a low viscosity mineral oil, which also servers to lubricate the bearing enclosed in the coupling. The pour point is such that the oil will pour at the lowest anticipated temperature, and has no corrosive effect on the steel parts of the unit.”

 

All well and nice, but not enough to figure out exactly what they used as fluid.  Later in the same document they talk about the types of metal used and the carbon-graphite seal.  Hum, carbon-graphite seal. 

 

I did some more digging for a few months and turned up a can of unopened original MOPAR Fluid Drive Oil.

 

An analysis of that oil, and some more literature I ran across, stated that the original fluid was a pure-base mineral oil with a Saybolt Viscosity of between 100 and 150. The fluid had a Viscosity Index of greater than 80.

The fluid had anti-foaming and anti-oxidation additives. It specifically did NOT have any seal swelling agents as these can attack the carbon-graphite seal and the copper in the bellows. This last specification eliminates most modern transmission fluids.

After finding several formulas to convert Saybolt Viscosities to Kinematic Viscosities, it appears that the best match to the original specification is ISO 22 or ISO 32 oil.

However, the ISO 22 is just below 100 Saybolt and the ISO 32 is much higher than 100 Saybolt.

Based on a period (c.1947) Lubrication Industry article on fluid couplings that had the following admonishment:

“Contrary to popular supposition any attempt to use a higher viscosity fluid would actually reduce the torque transmitting ability of the coupling since torque-transmission is dependent upon a high circulation of fluid between the impeller and runner and is not caused by any viscous drag between the two.”

 

During my continued research on the history of the Fluid Coupling, I ran across the fact that the original company that licensed the fluid coupling technology to Chrysler is still in business and still making fluid couplings for industrial applications. 

 

After a couple of weeks of digging, I found a senior engineer from that company that would have a long technical talk with me on fluid couplings.   In essence, he agreed with the period information I quoted above.  He added that the lowest viscosity oil that would still provide for bearing lubrication is the one to use in theory.  However, he did say that unless the fluid coupling bearing has been replaced and is know to be very high quality then err on the heavy side viscosity wise.  Just don’t over do it, he stated.

 

I was also told that normal hydraulic fluid does not have large amounts of anti-foaming agents in them as they usually do not have large amounts of air in the systems to foam in the first place. 

 

A fluid coupling is only filled to 80% and as such has lots of air in it.

 

Therefore, when looking for fluid coupling oil, one must look for an oil that is a “Circulating Oil” which has a lot of anti-foaming additives in it.

 

I was also informed that the additives tend to have a shelf life in the can, or in use, of 5 to 7 years and it should be changed at that time.

 

I was also told that the couplings are actually somewhat permeable and water vapor will work its way into and then back out, when hot, of a steel fluid coupling. Very little amounts, but apparently is does go on.

 

I was also told to never use engine oil or ATF as both would cause problems in the long run.

 

Based on the research and discussions I have come to the conclusion that ISO 32 hydraulic oil with the proper additives and VI (Viscosity Index) above 80 is a suitable replacement for the original MOPAR fluid drive fluid. ISO 22 would be a better exact match, but only if the quality and condition of the bearing is know in a particular coupling.

The oil I have identified that meets the specification, with a higher general viscosity to deal with the age of the bearings, is: Mobile DTE light circulating oil ISO 32. This oil is available at Granger. 

 

I have run this oil for about six months in San Francisco city traffic as well as up steep mountains on very hot days.  The coupling works well.  I have noticed, and other car people have as well, that the car seems to move out from a dead stop to 10 MPH better with the fluid.  Only a before and after session on a dynamometer would tell for sure, but I feel that it moves out much faster.

 

Classic car owners are advised to use this information at their own risk.  I am not a fluid coupling engineer, a bearing engineer, or a lubrication engineer. I have done my best to find out what was in the original MOPAR Fluid Drive Fluid. This effort is in essence industrial archeology and should be carefully considered prior to use.

 

As a post scrip in 2014.  I ran across and old Gyrol book that talks about the filling of the fluid couplings.  In short, how much you fill it affects the torque-stall curve.  Chrysler set that by the position of the hole in the bell housing.  However, if one is to fill it a little less or a little more one can change the curve.  Do so at you own risk and never fill it past 90% so it has air in it to compress less you blow the thing up!.

 

James Douglas

San Francisco

[Lumpy]

Wow! I always wondered why someone took the fluid drive out of Lumpy. When these cars began to get old, I suppose a lot of them were run with all sorts of strange stuff instead of the proper fluid, and then they failed or didn't work right. Poor Lumpy.

 

But that's okay, I like Lumpy just the way she is. But that sure was some interesting information.

 

ken