Recommended tranny fluid?

[72 'Ol Blue]

What is the recommended tranny fluid for a 72 F100 w/ a 4spd? I don't know the specific model of tranny, I just want to flush and put new fluid in. Thanks for any advice!

Also, is there a place on the web were I can find the original manual?

[mjhaltom]

90 wt gear oil?

[Johnm]

you can find manuals at www.lmctruck.com

[72 'Ol Blue]

90 wt gear oil?

that's what NAPA recommended and that's what I went with when I did it last fall. However, this past winter I had an odd occurrence. It was approx 20F outside and I went to move my truck and it would go into 1st and R, but when I let the clutch out, it would lunge a few inches then nothing (while in gear). I thought oh no, the clutch went out and left it till last week. I fired it up, put it in gear, drove no problem! Put it in reverse, no problem. The only thing I can think of is that the oil got so cold that it was not allowing things inside the transmission to do what they needed to do. That is an uneducated guess, but the only one I have right now as I'm not a mechanic, but sometimes I hang out under the shady tree

[spartman]

Try some 80-90 then if straight 90 is to thick

Otherwise go with a synthetic

IIRC some of the manuals said to put 40 or 50 weight engine oil in some of their trannies

[72 'Ol Blue]

thanks for the advice! I guess I'm in for some old fashioned trial and error to see what works best.

I just called the tranny shop down the street and they said they use 90W too (and out of curiosity I asked how much it would cost to drain and fill and they want $60, damn I'm glad I have tools and some knowledge).

[spartman]

OUCH on the price.

You could buy a case of really nice royal purple synthetic and still have enough for at least a beer for that kind of money.

One thing to remember with the synthetics is that if your gaskets are getting old it will leak right out.

[72 'Ol Blue]

which gaskets in particular? like i said i'm no mechanic but i learn at the rate of a sponge.

[spartman]

I believe there is one on top of the tranny where the shifter housing connects to the tranny.

There of course is the front seal and the rear seal.

probably one on the side where the pto could hook onto.

[72 'Ol Blue]

thanks, i will keep my eye on those spots if i go w/ synthetic oil. it leaks a bit right now but nothing serious. thanks for your help.

[spartman]

no problem

[mjhaltom]

$60 to drain and refill! Good God Almighty! I got a full set of gaskets and seals installed in my T-18 for $50 (labor only)

[averagef250]

The oil was probably just thick from the cold and made it feel like you were all the way in first or reverse when you weren't.

80/90 works fine. 90wt works fine. It doesn't matter the tiniest bit whatsoever. The thicker the oil the longer the bearings will last, but synchros may take a beating if you go too thick. Ford recommended filling the 435 4 speed with 50 wt non detergent motor oil after the initial 500 miles break in period from new in the bumpside era. Don't do this. 50 WT is too light. The bearings will not hold up under a heavy load.

The only seals are in the front bearing retainer around the input and the output yoke. Synthetic might make it shift a tiny bit better and might get you a MPG or so if you run it in the tranny, t-case and rear end. Synthetic is about $15 a quart though and you'll have to replace every seal if you run it.

[72 'Ol Blue]

thanks for the info! i think i'll try 80/90. although i won't know until next winter!