904 Low Gearset - Info needed

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80fbody

80fbody

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I'm tearing down an 81 lockup unit I have to see if it's got the low gearset. How do I tell? I assume I'll need to count teeth, just not sure which & what the number should be.

Thanks.
 
A998 or A999? It should be labeled on the bell housing. The A999 will have the low gearset.
 
Some '81 904''s got the low set. Then in '82 they all got it. These are all lockup tranny's of course. So even though this is only a 904 it may just have it. Just need to know which teeth to count & what the number should be. Tearing it down right now.
 
what does this do for performance wise for a 904 behind a 318? i am curious, i just rebuilt my 904, but used the stock gear set...
 
When you pull it apart below the rear clutch drum is a planetary set, that's first gear, remove the snap ring from the output shaft and remove that planetary set. Under it is the sun gear and shell, pull it out and compare the sun gear on either side of the shell. If the one in the front is larger than the one in the rear it's a low gear set. If they are the same size it's a standard gear trans.
 
mopardude318 said:
what does this do for performance wise for a 904 behind a 318? i am curious, i just rebuilt my 904, but used the stock gear set...
Click to expand...

It can really wake up a small cube low torque combo. It was worth about 2 tenths in my Duster with a 340.

I have two sets and would be willing to part with one of them.
 
Guitar Jones - Thanks for the tip & pm sent as well.

Leads me to another question - are there different low gear planets? aluminum vs steel, 3 vs 4, etc
 
Can you just verify I'm looking at the right piece. The gear on the outside is about 1.75" & the gear on the inside is roughly 2.375". So this is a low gearset, correct?

LowGear1.jpg

LowGear2.jpg
 
Guitar Jones said:
When you pull it apart below the rear clutch drum is a planetary set, that's first gear, remove the snap ring from the output shaft and remove that planetary set. Under it is the sun gear and shell, pull it out and compare the sun gear on either side of the shell. If the one in the front is larger than the one in the rear it's a low gear set. If they are the same size it's a standard gear trans.
Click to expand...

This right here is dead nuts on.


Also, I want to correct a glaring error made earlier. ALL low gearset (A999) transmissions are NOT lockup transmissions. Both the A998 and A999 were available in non lockup style. I have had several of each. The A998 came with a 4 disc direct drum, 4 pinion planets and a standard first gear set. The A999 had a 5 disc direct drum 4 pinion planets and the low gearset. Both were available in lockup and non lockup.
 
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