904/500 low gear set interchange???

Posted By: Mr.Mopar

904/500 low gear set interchange??? - 01/26/10 05:48 PM

I went to the junkyard today, and came across a A500 trans laying in the back of a ramcharger, and i didnt think about it till i got home.. would the low gear set out of a 90's A500 fit a 70's A904 trans?? it would be awesome to have that extra gear pulling out

Posted By: zzyzxpat

Re: 904/500 low gear set interchange??? - 01/27/10 03:12 AM

You will never notice the difference.

Posted By: Mr.Mopar

Re: 904/500 low gear set interchange??? - 01/27/10 10:49 AM

Quote:

You will never notice the difference.

well.. i went from 2.94 gears to 3.23 in my duster and i went from 14.0 to 13.6 at the track...

so I would think that changing the gear ratio in the trans would do about the same thing..

can anyone tell me if the parts will fit??

Posted By: patrick

Re: 904/500 low gear set interchange??? - 01/27/10 01:47 PM

they should, I think you may need the drum from the LG tranny, too...Hopefully John Kunkel will chime in...he seems to be the answer man for torqueflights.

Posted By: zzyzxpat

Re: 904/500 low gear set interchange??? - 01/27/10 01:53 PM

Yes the parts will fit. You need the front ring gear and hub assy, the front planet, and the sun gear/shell assy. It's a drop in replacement.
I am sure changing gears in the diff did change your E.T. That changes the RPM throughout the entire range. Changing the gears in the trans changes 1st gear ratio only.

Posted By: DJVCuda

Re: 904/500 low gear set interchange??? - 01/27/10 02:34 PM

Quote:

Yes the parts will fit. You need the front ring gear and hub assy, the front planet, and the sun gear/shell assy. It's a drop in replacement.
I am sure changing gears in the diff did change your E.T. That changes the RPM throughout the entire range. Changing the gears in the trans changes 1st gear ratio only.

that is incorrect - it changes 1 & 2

Posted By: patrick

Re: 904/500 low gear set interchange??? - 01/27/10 05:26 PM

Quote:

Quote:

Yes the parts will fit. You need the front ring gear and hub assy, the front planet, and the sun gear/shell assy. It's a drop in replacement.
I am sure changing gears in the diff did change your E.T. That changes the RPM throughout the entire range. Changing the gears in the trans changes 1st gear ratio only.

that is incorrect - it changes 1 & 2

yup, older 904's are 2.45/1.45/direct, newer ones are 2.74/1.54/direct

Posted By: DJVCuda

Re: 904/500 low gear set interchange??? - 01/27/10 07:18 PM

THANKS!

Posted By: Dakota_Don

Re: 904/500 low gear set interchange??? - 01/27/10 07:25 PM

ok so lets do some math, if he has a 904 with 3.23 gears and he adds the lower gear set to this trans, what would be his new first and second drive ratio, then for kicks add the a500 OD final ratio, lets keep everything equal.

Posted By: gremlinsteve

Re: 904/500 low gear set interchange??? - 01/27/10 08:13 PM

the 999 amc wil also interchange.

steve

Posted By: patrick

Re: 904/500 low gear set interchange??? - 01/27/10 10:14 PM

Quote:

ok so lets do some math, if he has a 904 with 3.23 gears and he adds the lower gear set to this trans, what would be his new first and second drive ratio, then for kicks add the a500 OD final ratio, lets keep everything equal.

math is easy...2.74*3.23=8.8502

8.8502/2.45= 3.61
so overall 1st gear will act like it's a standard trans with a 3.61 rear.

do the same math for 2nd if you're curious.

3.23*0.69 = 2.23, or overall gearing like 3rd in a late model M (which used 2.21 gears mainly)

Posted By: Mr.Mopar

Re: 904/500 low gear set interchange??? - 01/27/10 10:14 PM

glad to hear the parts should work!

I'll try to get them this weekend. And i did know that it only changes first and second. I just think it would be nice to have basically an "extra" gear in fisrt for pulling out at the track, then on the street your 3rd gear is still the same.