Questions about 904 transmission upgrades

[jboucher250]

Hi,

I have been doing a lot of research on upgrades for my 1972 Dodge Charger with the original 904 transmission. One of the items that many people mentioned upgrading was the front planetary from the original 3 pinion aluminum to a 4 pinion steel. I ordered and received a used 4 pinion steel planetary and now have some questions.

First, there was a mislabel on the item I ordered and it did not come with the ring gear. I contacted the seller, and they are willing to send one to me but are asking whether I need the 2 tab or 1 tab washer. Which one do I need and what is the difference? This has also made me wonder, what else do I need to make this planetary upgrade? Washers, snap rings, spacer? In other words, based on this diagram, which part numbers do I need to make this planetary work in my transmission: https://www.wittrans.com/dx/wittrans/90.html?type=90? I also notice some differences like the sun gear when I compare it to the picture in my 1972 Dodge Chassis manual (pictured attached).

Secondly, attached is a pic of the planetary they sent me, I noticed some wear inside. There is a grove and a hump created in it. Is that a problem? What causes that wear?

Thanks

 

[miller]

Secondly, attached is a pic of the planetary they sent me, I noticed some wear inside. There is a grove and a hump created in it. Is that a problem? What causes that wear?

Never fooled with a 904, but plenty of 727s. The tab washer, probably depends on the year model 904. But, anything like that can easily be bought separate...just get a 'complete' overhaul kit for that year 904.
From the diagram, looks like a thrust washer goes where the wear is your asking about. Hard to say, without in hand! Almost looks like the thrust washer was mounted backwards, creating that wear???
Toss a handful of common sense at the part, to decide if it's gonna do what you want it to do. Your the one with the final call.
Yeah, on my current 727 build (years ago, now), I updated my pinion carriers. But, all your doing is adding pinion gears, to help carry the load.

 

[jboucher250]

I have a long list of other things that I will be upgrading with this front planetary and priced out the parts separately.

Recommendations for upgrading the front planetary were that the early model aluminum ones had issue with the splines, not necessarily the number of pinions.

 

[jboucher250]

That is a good idea though, I bet the washer was in backward and dug the tab/tabs in.

 

[moper]

IMO - if that is a worn groove, that planetary is not one I'd ever use. I guess I'm confused on the rationale behind replacing it too. It takes a lot of power to break one. I've upgraded probably 3-4 727s before, mainly because of the power output going in front of it. If you're not making 500hp, there's little reason to change that particular set of parts. You are better served replacing the single wound spring in the front clutch with a multi-spring (727 type) spring design in a new aftermarket drum.

 

[jboucher250]

From my research I have found that the 727 had a steel planetary opposed to the aluminum explaining why they never had issue ripping the splines like the early 904. I do plan on putting some power to this thing hopefully starting around 450. Also, the 24 spring setup on the front drum is one of the many items on my list of upgrades.

 

[moper]

I think you are still a little misinformed. In almost 30 years of doing them have yet to find a factory steel planetary carrier in any Torqflite. While I have sheared off the housing of the sprague from the case, shattered the planet carrier, broken bands, etc. I've never, ever stripped the splines off a pinion. Even in my B wedge C body with nitrous. However, there are those who have used the 4sp auto modern 4-pinion planets in 727s, and those definately strip because the spline counts are slightly different between the 4sp and the 727. Your results may vary, but I think you are in at least the case of a steel planetary chasing a unicorn when a horse will do.

 

[jboucher250]

Thanks for the info. Here is an example of one of the forums where people mention the value of upgrading to the steel planetary: http://board.moparts.org/ubbthreads...309/904-aluminum-vs-steel-planetary-sets.html. Also, the last post on this page is one of the examples of someone mentioning steel planetaries in later models: http://www.forabodiesonly.com/mopar/threads/904-race-tranny-recipe.256475/.

While I value the opinion as to whether or not this upgrade is absolutely necessary, I will probably go with a steel planetary because it is a cheap investment once I already have the transmission apart.

Nonethess, I still seek input on my original questions:

Is the planetary set that I received (pictured above) damaged?
What they are talking about when they ask me whether I want the ring gear with the one tab washer or the two tab washer?

Thanks

 

[miller]

Is the planetary set that I received (pictured above) damaged?
What they are talking about when they ask me whether I want the ring gear with the one tab washer or the two tab washer?

Damaged...yes. Reality says they should not sell 'damaged' parts, but, takes all kinds.
Again, no experience on 904s, so only guessing the ring gear is year related. Look over your ajoining parts...might be able to figure it out. Seems with a good 904 parts book, and knowing the year, would tell which one.

 

[moper]

I agree - damaged.
Something to note on those links - they are referencing building A999s predomimently. Not 904s. Admittedly, 999/904s are not one of my most familiar deals. I've built more than a couple but they were a ways before a lot of the improved parts came out.
Perhaps the best info I can provide would be do your homework. I would call someone like John Cope and talk to him. There's a lot more available now than there used to be as a lot of guys are using them in much higher powered cars but you want to make sure it will work all together.