New kick down bands

[Camtron]

New kick down bands; one of these is a re-lined OEM factory replacement and one of these is a poorly stamped replacement that comes in most rebuild kits. Cheaply stamped detent/lug to hold the kickdown adjustment bolt in place vs the three wall/dog ear tabs and back wall to make sure it all says put under load.

Just when you think your rebuild kit has everything you need, you may find yourself ordering certain parts individually.

This also makes it pretty quick and easy to tell if your 904/999 has been rebuilt as most rebuild kits have been using these cheap stamped bands for years. This one came in my kit from, Oregon Performance Transmission.

 

[Duke5A]

I really do commend you Camtron. For all the work I've done to my car I've never opened a transmission further than the valve body. Always just took the magic slush box to a shop and tell them, "do the thing."

If you plan on another trip up here I've got more parts for you. If you need a BB 727 I've got a buddy with a few too.

 

[Camtron]

I really do commend you Camtron. For all the work I've done to my car I've never opened a transmission further than the valve body. Always just took the magic slush box to a shop and tell them, "do the thing."

If you plan on another trip up here I've got more parts for you. If you need a BB 727 I've got a buddy with a few too.

I appreciate that very much. I’m definitely still learning basics but I’m trying. I don’t need to be the guy that can rebuild them between races but I like knowing I can do it in the garage and what little changes can be done to improve things without breaking the bank.
That’s funny, the valve body is what intimidates me the most still. Terrified of dropping one of the little check valve balls, lol I have a stage 2 shift kit I really want to add to this rebuild though. First one I did was just a quick and dirty rebuild to get moving again. It’s worked but I know or at least feel like I’m still on borrowed time, lol

 

[Mikes5thAve]

I've never dug too far into one either but I've got at least 3 dead 904s kicking around that I really want to open up sometime..

 

[Camtron]

I've never dug too far into one either but I've got at least 3 dead 904s kicking around that I really want to open up sometime..

I got a Tom Hand bench manual and went for it. There’s a few manuals, they all seem a little incomplete in their own ways and tend to lean more towards 727s and imply just do the same general steps with a 904 even though it’s a little different with its parts.
The FB 727 builder group has been super helpful too when I’ve asked questions.
So with that, this new band is for an A500 it’s a little wider and when paired with a 3.8 ratio servo lever will make for some solid clamping force to give some nice solid shifts in/out of second with limited wear to the band and drum.
There’s a number of different band options, lining options, springs/servo levers, ect that you can pick from from venders like CopeRacing or A&A Transmission, or whoever, that are easy enough to swap/replace and improve shifting without breaking the bank.

 

[Sub03]

I second that Camtron. I ordered the Tom Hand manual when I did my 904. I found it was more detailed than the ATSG manual I had on my computer. It was a satisfying feeling taking it apart and clean every little piece before putting it together again with new hardware and seals.
I did screw up one thing though. I had a rpm flare on 2-3 shifts on WOT. Somehow i did manage to install the kickdown servo piston rod the wrong way, so the front band released a little early. Lucky for me that was fixable without removing the tranny from the car.

Mike, if you have 3 dead 904s I reccomend you order the Tom Hand manual and a bucket of transmission assembly grease and give it a go.

 

[Camtron]

One too many kick down band adjustments and a few too many hard shifts and, you’ll be in for a bad time.
That’s the front drum out of my original trans next to its new replacement from A&A Transmission in Indiana.

 

[Duke5A]

Do the 904 cast drums go kaboom like the 727 drums do? When the 518 comes out it's getting a steel drum.

 

[Camtron]

Do the 904 cast drums go kaboom like the 727 drums do? When the 518 comes out it's getting a steel drum.

No! At least from my one experience so far and what I’ve seen/read online. Apparently that’s just an issue with the longer/heavier drums in the 727s. I was spinning the thing like a pissed off teenager to get it home when it started letting loose. Ate a good 1/8” + out of the drum and busted some clutch teeth but, made it home. Good way to make 4 miles seem like 400 after a day of work.

Was like a metallic crime scene.

 

[Camtron]

Which, I’m sure maybe legit high RPMs from a strong, high revving race motor with high ratio servo lever and high friction band, maybe a 904 drum turns grenade but not normal failure otherwise.

 

[Mikes5thAve]

Mike, if you have 3 dead 904s I reccomend you order the Tom Hand manual and a bucket of transmission assembly grease and give it a go.

My solution was to go 727. But I figure hey I have these transmissions I might as well try doing a rebuild on one of them! I'll have to watch for the Tom Hand book.

 

[Aspen500]

Barring a previous fracture crack in the cast iron drum and "spirited driving", from my understanding, the most common cause of drum explosion is failure of the sprag and high engine rpm. The drum can end up spinning more than twice engine rpm. 6,000 rpm equals maybe 14,000 rpm of the drum, kaboom. I've seen the aftermath of drum explosions and it's not pretty. Sometimes doesn't do the driver (or passenger) any favors either.

Not really sure if it's the actual rpm the drum gets up to, or the fact that it more than doubles it's rpm in a basically in a split second that causes drum failure.

 

[Camtron]

Barring a previous fracture crack in the cast iron drum and "spirited driving", from my understanding, the most common cause of drum explosion is failure of the sprag and high engine rpm. The drum can end up spinning more than twice engine rpm. 6,000 rpm equals maybe 14,000 rpm of the drum, kaboom. I've seen the aftermath of drum explosions and it's not pretty. Sometimes doesn't do the driver (or passenger) any favors either.

Not really sure if it's the actual rpm the drum gets up to, or the fact that it more than doubles it's rpm in a basically in a split second that causes drum failure.

Yea, very true but it’s also still not as common for a 904 to let loose with a bang as the 727 due to the mass of the 727 drum. Then again on average you don’t see nearly as many 904s behind builds with enough torque to roll the sprag like that. So maybe it’s just the difference in the numbers of how many more 727s are being built/put behind built motors vs built 904s that get ran hard at the tracks. I’m just regurgitating what I’ve been reading lately on A body and 727 groups while I’ve been tearing mine open.

 

[Camtron]

Even with the “904s can be built to take blah, blah, blah and run .20 seconds faster” it doesn’t seem like enough guys spend the money on it to make the support worth while anymore. Cope doesn’t offer much for 904s anymore he’ll even chime in on the FB group and tell guys to build 727s, A&A has 904 parts but is 727 focused, Keith at 727 specialties is well just that he can build you a 904 but has 727s ready to run. It’s getting harder to find 904 race parts but 727 is still everywhere.

 

[Camtron]

just got the last of what I needed/wanted ordered for this 999 I’m putting together. Hi performance red lined low/reverse band, billet 1 piece rear servo and spring, double seal billet accumulator, billet 4.2 ratio apply lever and front band strut and a reverse wound clutch spring for the front drum.
Now I just need to find a shop to do the stage 2 shift kit for me. There’s a slot that has to get cut into the valve body that I’d rather not hack out in the garage. I’m comfortable doing the drilling but I want the slot to be cut nice and clean and I’m fairly confident I can’t do it at home.
I’m pretty excited to get these parts in and finally get this trans together. It should shift super firm with no overlap between the gears and make for a pretty stout trans behind the 5.9mag that’s in the car; so I can give it all the damn beans all the damn time and send it around, Chicago, lol

 

[GTX JOHN]

ProTrans supplies all the parts for 904 for racing.
We routinely run well over 500 HP in our Superstock
cars.

 

[Camtron]

ProTrans supplies all the parts for 904 for racing.
We routinely run well over 500 HP in our Superstock
cars.

I’ll check them out for the next 999 or 727 build I do. I used A&A, Cope, Mr. Randy (eBay seller) and Oregon performance for this one that I’ll hopefully be putting together next weekend.