How would one go about checking the gear oil in the 3 speed manual trans? How much does it take, and is there any recommendation of fluid besides regular gear oil and some lucas to slow the leak?

When I have to put a clutch in it, ill be replacing the rear main seal in the motor and will re-seal the trans so this is only temporary.

I know I could probably find it if I looked for it, but Its dark out and I want to know what to look for. Only reason I thought about this is because while I was under there adjusting the linkage I noticed Ive got a bad output shaft seal and the bottom of the trans was wet.

 

This is what I do.
1) Jack up front passenger side of truck. This is so tranny fluid doesn't leak out when you remove the plug.
2) Remove plug from transmisstion on passanger side of truck, you can't miss it, points upwards at about a 45 degree angle.
3) I bought a transmission oil jug with a pump, so I just pump in fluid until it starts to overflow.
4) Screw plug back in.

It's pretty simple, fill it as full as you can.

 

It's pretty simple, fill it as full as you can.[/QUOTE]

Actually, this may be correct for a 45 degree fill hole. With the horizontal fill hole, you just fill the fluid up to the bottom threads of the plug hole. IE; just until the fluid just starts to run out. Same for the differential. Stick your finger in the hole ...the fluid should be level with the bottom threads of the access hole with mayby a little running/dripping out. )))

This allows for fluid expansion, etc.

 

I am interested to know what spec fluid to use as well. I believe we are not supposed to use GL-5 spec gear oil. ( corrosion of syncros? is that right) I have found 140 w GL-4 gear oil, but no 75 through 90 in GL-4 only GL-5. Can I use straight 50w motor oil? It doesnt meet Gearl Lube spec though.

 

Thanks fellas.

Found my 1978 manual, it says

standard transmission lube. C3RZ-19C547-B
OR D8OZ-19C547-A
ford spec- ESP--M2C83-C

 

The 50w motor oil is fine, in a NP 435 4 speed anyway. Better shifts in cold weather, etc. There are old posts from tranny guru's on this site with specifics about this. That is what convinced me convert to 50w motor oil a few years ago in my tranny. I have no shifting or excessive wear problems what so ever.

 

You can't overfill, it will run out the hole. Motor oil and gear oil are rated different. 50w motor oil has same viscosity as 90w gear oil. I use Lucas gear oil in everything, rated for GL3,4,5. Makes things simple.

 

Thanks Riderman. I removed my 3spd, bellhousing, and clutch yesterday. When I drained it, it was very very black, it smelled like a mixture of gear oil and used atf dextron, very very thin. The clutch was very worn, the springs in the old one are very loose and rattley. I think I may have a transmission problem as well. In neutral it still wants to lightly turn the output shaft. I will find out today when it goes back together. I may have to take it back out and figure out whats wrong inside, or it may just work great with new fluid and a new clutch.

 

Hey, mine did that too. The input shaft still turns the output while in neutral. Pretty sure its just the oil moving around because other than that, my trans is fine.

 

Mine is not so much. LOL Its got definite problems.

 

Ouch man, that sucks. Any idea what the problems are?

 

I can offer a description of what it does, but not what the actual repair is. https://www.ford-trucks.com/forums/1...procedure.html

Here is the thread discussing it. Over time I will get it fixed, but first the plan is to make it roll. LOL
My wife works nights, I work days, three kids, one is only 15 months old. They are out of town untill thursday night, so I gotta get this thing rolling before I turn back into superdad the babysitting, yardworking, cleaning, feeding, gardening, cooking, and loving machine. LOL Also every other weekend I have been restoring two motorcycles for my boss's sons. 1974 cb350 is done and riding, the 1971 cl350 scrambler is a painted frame, with engine, and triple tree installed. Like we said in the submarine fleet. You can sleep when your dead. LOL

 

Use 80W-90 gear oil. You can also use 75W-90 synthetic(great in cold weather). Do not use the moter oil. Motor oil does not have the EP (extreme pressure) additives necessary for use in this transmission. The viscosities of the two oils are similiar, but the chemical formulation is entirely different.

 

I used 75w90 synth, but its sitting in a bad trans. LOL I will use it on the new used one as well.