A903 3 on tree trans fluid

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Johnny71dusty

Johnny71dusty

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I’ve read many threads on this wirh many opinions.

1971 duster with a903 . 3 on tree style trans . It’s great and I’m in proses of converting to 4 speed overdrive but in mean time I want this thing to have fresh fluids before power tour .



What is supposed to be in this ? ATF ? Dex 3 ?

what about the 7 1/4 rear ? What oil or fluid for that ? I’m trying to get all stuff to do this this weekend.
 
I put Dexron in mine. It works good.
 
can't go wrong with gear oil .ATF ,well it may be ok but then again . Been running 75 / 90 gear oil for over 50 years with no problems
 
Up here in canuckistan, atf is widely used as its -200 364 days a year.further south a guy would benefit with a heavier oil, such as 80w90 to make trans quieter, and reduce wear. The downfall is perhaps diffuculty shifting on cooler days. Could go 50/50 with gear oil and dexron.
 
Johnny71dusty said:
Dex 3 ? I don’t know the difference
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When these transmissions were new, DEXRON was all there was. I would run original Dexron, IF I could find it. I think all you will be able to find is Dexron 3 and that's fine. Each Dexron generation supersedes the last, but I wouldn't waste the money on Dexron 6. It just doesn't need "all that".
 
Johnny71dusty said:
I’ve read many threads on this wirh many opinions.

1971 duster with a903 . 3 on tree style trans . It’s great and I’m in proses of converting to 4 speed overdrive but in mean time I want this thing to have fresh fluids before power tour .
What is supposed to be in this ? ATF ? Dex 3 ?
what about the 7 1/4 rear ? What oil or fluid for that ? I’m trying to get all stuff to do this this weekend.
Click to expand...

Run over to MyMopar and download yourself a free service manual. From page 0-24 right in the front of the manual. PLEASE READ ALL OF THIS

0-24.jpg
 
It seems Mopar used the climate to dictate what fluid to use. ATF doesnt get crazy thick in cold weather so they use that in northern climates and out the door off the line. As it states it can be replaced with 90w or even 140w in warmer climates. There are no syncros in a 903 iirc so there is no special ingredient. Gear oil most definately in the rear. Dexron is backards compatible to all numbers, the highest Dexron is usually 100% synthetic, not needed in a manual.
 
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