904 low gear set- what vehicles and what parts?

Posted By: mshred

904 low gear set- what vehicles and what parts? - 10/29/12 03:48 PM

Hey guys,

I would like to do the low gear swap on my 72 year 904 transmission. My transmission currently has aluminum 4 pinion planets front and rear.

My first question- what vehicles have low gear set transmissions? My local wreckers is scarce for 80's year chryslers, so later model stuff like dakota trucks, 6cyl jeeps, late model rams, etc. is all I really have to pick from. What year vehicles would have the transmissions I am looking for?

Second- when I get the transmission apart, what parts am I looking for from it? I have read that the planetaries are steel in these transmissions- can I swap both in to my current 72 year aluminum planet trans? Are there any other mods to get the low gear set to work?

Thanks!

Posted By: plumcuda

Re: 904 low gear set- what vehicles and what parts? - 10/29/12 06:39 PM

When I did that swap,I found a 904 from a slant six D100 pickup.

Posted By: roe

Re: 904 low gear set- what vehicles and what parts? - 10/29/12 08:07 PM

The guy who built my Trans for me said they come in the jeeps, but didn't specify what years.

Posted By: mshred

Re: 904 low gear set- what vehicles and what parts? - 10/29/12 08:27 PM

Wondering if the A-500 trans will work for parts as there is one local to me for 100 bucks. Also wondering if the planetaries are steel and if both front and rear will swap into the 904?

Posted By: John_Kunkel

Re: 904 low gear set- what vehicles and what parts? - 10/29/12 09:20 PM

Any '82 or later trans from the 904 family will have the low gearset.

Posted By: Dakota_Don

Re: 904 low gear set- what vehicles and what parts? - 10/29/12 10:33 PM

Quote:

Wondering if the A-500 trans will work for parts as there is one local to me for 100 bucks. Also wondering if the planetaries are steel and if both front and rear will swap into the 904?

yup

Posted By: mshred

Re: 904 low gear set- what vehicles and what parts? - 10/30/12 12:14 AM

Quote:

Quote:

Wondering if the A-500 trans will work for parts as there is one local to me for 100 bucks. Also wondering if the planetaries are steel and if both front and rear will swap into the 904?

yup

Both planetaries are steel? What parts do I need to actually swap in from the A-500 into the older trans to complete the swap?

Posted By: mshred

Re: 904 low gear set- what vehicles and what parts? - 10/30/12 05:27 AM

I have heard some people mention that some A-500's are not low gear set???

Is there a way to verify from the outside? This is coming out of a 89 dodge D150 2 wheel drive truck if that makes a difference

Posted By: 360view

Re: 904 low gear set- what vehicles and what parts? - 10/30/12 02:45 PM

Is it possible to swap and or modify
the low 904 gearset
into the OD unit of a 46RH somehow?

The planetary of the OD unit
is supposed to be
the front planetary of a 727
Spun in 1 divided by 1.45 = 0.69 ratio

1 divided by 1.54 = 0.65
Would be a lower numerical overdrive

I have to rebuild my OD in my 46RH after 190,000 miles so it will be pulled soon anyway.

The AA price for 727 low gearsets is $900 plus.

Posted By: mshred

Re: 904 low gear set- what vehicles and what parts? - 11/02/12 01:33 AM

I also got to wondering about the front drum and whether or not the A-500's have a 5 clutch front drum and if it can be swapped into the older trans with no issues?

Posted By: John_Kunkel

Re: 904 low gear set- what vehicles and what parts? - 11/02/12 07:33 PM

Quote:

I have heard some people mention that some A-500's are not low gear set???

All A500's have the low gearset.

Posted By: mshred

Re: 904 low gear set- what vehicles and what parts? - 11/02/12 07:38 PM

Quote:

Quote:

I have heard some people mention that some A-500's are not low gear set???

All A500's have the low gearset.

John, does the A-500 have a 5 clutch front drum that is swapable into earlier 904's? or are there issues with the pump when doing this?

Posted By: 70AARcuda

Re: 904 low gear set- what vehicles and what parts? - 11/02/12 08:44 PM

you can put 5 disc and steels in a 4 disc clutch pac...

just use the thin .068 disc..and .061 steels..i might have the thickness backwards...but they are the same thickness that the rear drum uses..

you should end up with .050 clearance...i usually have the pressure plate ground .010 to clean it up and get a few thousands extra clearance.

Posted By: John_Kunkel

Re: 904 low gear set- what vehicles and what parts? - 11/02/12 11:40 PM

the A500 will have a 5-clutch front drum.

To use the 5-clutch drum in an earlier 904 you need the matching front pump or need to modify the existing front pump.

Posted By: mshred

Re: 904 low gear set- what vehicles and what parts? - 11/03/12 12:18 AM

Quote:

the A500 will have a 5-clutch front drum.

To use the 5-clutch drum in an earlier 904 you need the matching front pump or need to modify the existing front pump.

So If I take the front pump from the same A-500 trans, then it should work with no other modifications?

Posted By: John_Kunkel

Re: 904 low gear set- what vehicles and what parts? - 11/03/12 08:50 PM

It gets a little complicated, if the 904 is pre-'78 you can get in trouble mixing parts; if the 904 is '78 or later non-lockup you can use the later 5-clutch drum and pump but if the 904 is pre-'78 you'll also need the later input shaft and rear clutch piston retainer.

Or the earlier pump can be machined to accept the 5-clutch drum.

Posted By: mshred

Re: 904 low gear set- what vehicles and what parts? - 11/03/12 09:37 PM

Quote:

It gets a little complicated, if the 904 is pre-'78 you can get in trouble mixing parts; if the 904 is '78 or later non-lockup you can use the later 5-clutch drum and pump but if the 904 is pre-'78 you'll also need the later input shaft and rear clutch piston retainer.

Or the earlier pump can be machined to accept the 5-clutch drum.

Are there any threads that explain what has to be machined? Or is it kinda obvious when looking at the parts what would have to happen?

Thanks for the info John

Posted By: Anonymous

Re: 904 low gear set- what vehicles and what parts? - 11/04/12 12:18 AM

Personally, I wouldn't bother.

I did it a few years back and there really wasn't a difference in a street car.

If you looking for every last hundredth in class racer it may be worth it but otherwise you can save your money and time.

Posted By: roe

Re: 904 low gear set- what vehicles and what parts? - 11/04/12 01:03 AM

I don't know about that. I just had my 904 rebuilt with a transgo shift kit, low gearset, and a factory high stall converter, and left in my 2.76 rear gears. My car woke up like u wouldn't believe. Much quickening the line, breaks loose my org leg so much easier, even with heavy 22" rims and and a highway rear gear. It could be a combination of everything though.

roe

Posted By: mshred

Re: 904 low gear set- what vehicles and what parts? - 11/04/12 05:29 AM

Quote:

Personally, I wouldn't bother.

I did it a few years back and there really wasn't a difference in a street car.

If you looking for every last hundredth in class racer it may be worth it but otherwise you can save your money and time.

running in a heads up class where im trying to ring every last bit out of the car

Posted By: Anonymous

Re: 904 low gear set- what vehicles and what parts? - 11/04/12 05:43 AM

I bought my sun gear and planetaries from a local transmission supplier.

Chance Transmissions here in Wichita.

Paid $50 but that was ~ten+ years ago?