PROPER Filling of '51 Car 3 sp/od

[Shoebox]

So I received my Jug of Sta-lube 90 wt GL-4 and am ready to fill my '51 3spd w/od. The Green Book clearly states to fill (4 1/2 pints) all into the main trans fill hole. There is a substantial size fill plug in the aft portion of the trans,....why?


I recall my dear Dad once recalling how he damaged the trans in his old hunting Ford wagon because he didn't know there were 2 fill holes. Just need to get this done correctly. Thanks.

[mcgarrett]

Pour or pump the lube in slowly into both the tranny and the overdrive unit so it has time to level inside the gearcases. When it starts to run out the filler plug holes they're full. Make sure you have the OD solenoid installed with the correct O-ring or it will leak out and make a mess!

[mcgarrett]

Shoebox,
Let me add some important clarification to what I just posted about your question.

Reading from page 15 of the Borg Warner Overdrive service manual, it states:

"The transmission and overdrive unit are connected with oil passages so that the same oil is used for both. However, certain precautions must be used in the filling order that the proper amount of oil may be carried.

In making the initial filling, first fill the overdrive unit with the proper oil until it runs out the filling hole, then replace the plug. Then fill the transmission with the same oil until it runs out the filling hole, and replace the plug.

In subsequent filling (at each chassis lubrication), inspect the transmission only for oil level and fill as necessary.

The manufacturer of the overdrive unit recommends only straight mineral oil, not the "EP" or extreme pressure types of lubricant, which are unnecessary for the overdrive and may contain ingredients that will corrode or otherwise damage the parts, or form sludge or contain solid matter in suspension which may stop the oil passages to the pinion bearings resulting in serious and expensive damage to the unit. UNDER NO CIRCUMSTANCES MUST A LUBRICANT OF THE HYPOID AXLE TYPE BE USED IN THE OVERDRIVE.

The most satisfactory all-round lubricant for the overdrive is SAE No. 40 engine oil of a good grade. For extremely hard driving in hot climates, SAE No. 50 may be used.

Straight mineral oils of the transmission type SAE No. 80 for all-round use, or No. 90 for hard driving in hot climates will also be satisfactory."


The text in blue is directly quoted from the BW service manual. I added underlining and bold type for emphasis. I hope this is helpful to you.

[rotorwrench]

Back in the day, the GL 3 lubricant was used. This was low EP by their discriptions. GL4 was the replacement which is also a low EP formula.

I'm in a pretty warm climate part of the country down here in south central Texas so I use SAE 50 Aeroshell 100W ashless dispersant motor oil. NO PLUS type. The plus/+ has tricresyl phosphate additive for Lycoming engines. They have straight 100 mineral but the AD oil keeps the trans cleaner. SAE 50 motor oil is the same viscosity as SAE 90 gear lubricant. Cooler weather areas can use lower viscosities.

The sprag clutch back in the tail housing would not do well with any larger amount of EP additive. The thrust washers and reverse idler bushing in the trans don't work well with high EP either.

[38 coupe]

My experience is that some of the R10 overdrives have the fill plug located right where the large diameter drum for the overrunning unit lives. The space between the overdrive case and the guts are so small that filling is sometimes not realistically possible. In those situations I leave both fill plugs out and fill through the transmission only. The transmission will start to leak out first, shove the transmission fill plug in quickly. The overdrive then should start to leak out the fill plug so you know the whole unit is full. If the overdrive doesn't come up to full. I don't remember ever having this fail to work for me.
Also, depending on how you jack up the car to check your transmission one of the fill plugs will probably be higher than the other. That will affect how full each fill plug level checks when performing maintenance.

[Shoebox]

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Originally Posted by 38 coupe

My experience is that some of the R10 overdrives have the fill plug located right where the large diameter drum for the overrunning unit lives. The space between the overdrive case and the guts are so small that filling is sometimes not realistically possible. In those situations I leave both fill plugs out and fill through the transmission only. The transmission will start to leak out first, shove the transmission fill plug in quickly. The overdrive then should start to leak out the fill plug so you know the whole unit is full. If the overdrive doesn't come up to full. I don't remember ever having this fail to work for me.
Also, depending on how you jack up the car to check your transmission one of the fill plugs will probably be higher than the other. That will affect how full each fill plug level checks when performing maintenance.

38 coupe, I believe this is what the Ford Green Book had in mind when it stated to "fill just through the main fill hole". Mac Van Pelt said he didn't know how much the OD side held and suggested it would do no harm to put about 16 oz in there to start, and then fill the main body till it drips out. Then let it set awhile to allow it to level out, so that's what I did.