tci 904 or built 727

-
Bill Dedman said:
One thing I need is a "ground" (lightened) governor weight that will allow me to run the car at the strip without having to manually hold it in 1st gear. I have a friend who has a 390hp crate 360 Magnum-powered '69 Dart GT, and when they rebuilt his transmission, prior to installation, they ground his governor weight so that the automatic 1-2 upshift at full throttle comes at 5.800 rpm. He can start with his selector in "2", and ignore it 'til he needs to shift into 3rd gear.

I want that, too.

I wonder if there's a spec for the weight of that governor to accomplish this?
Might just be a trial-and-error deal, but they got it right on the first try on his transmission. It works great!

The guy who built his transmission retired and sold the business, so I can't ask him...:angry7:

Anybody reading this have any experience with this procedure?

Bill, in Conway, Arkansas
Click to expand...

Most any good performance trans shops sell them. Andrews Racing, Cope Racing, A&A just to name a few.

Even Mopar perf. used to sell them but I'm not sure if they still do.
 
what do you do with the gov. if you have a manual Valve body?
 
74Burntorange said:
what do you do with the gov. if you have a manual Valve body?
Click to expand...

Nothing. The manual VB bypasses any functions the governor does so it's like it's not in the circuit any longer. Some racers go as far as removing the governor for weight savings. That's for those guys looking for every last .005 sec.
 
The part that explodes is the sintered iron front clutch drum. It explodes because the sprague gets damaged. They get damaged in a lot of ways, but the ones I see have never turned in the case. the steel fingers are simple sheet metal, and the rollers or fingers break or flatten, and then the forward drum loses it's fixed anchor. The sprague can turn in the case, but the bolt in spragues run bolts thru the case to stop the turning. Still doesnt stop the fingers straightening out...lol. So the best way to do it is to get rid of the drum and replace it with a steel unit that holds more frictions, and has the multi-spring piston.

I have a buddy who runs the C4 in his car, I was simply using the metric trans as an example of "good because no-one uses them".

On the governors... using the A&A ones with Cheetas or modified valve bodies may end up with a different rpm than what you bought them for... Just an FYI...
 
>>>The part that explodes is the sintered iron front clutch drum.<<<

Is that drum ever replaced with an aluminum one? I have seen aluminum clutch drums, but I don't know where they fit in the case.

My valve body is un-altered except for the transmission received a Trans-Go shift kit when Len rebuilt it. You think it would be okay for a light governor? That is, should it still shift at the intended pre-determined rpm?

It would sure be nice, not to have to manualy make that 1-2 shift.

Thanks for any info, and thanks for the explanation on the sprag damage, and how it happens.

Bill, in Conway, Arkansas
 
They have steel drums, and aluminum ones. The steel is because the wear surfaces of the drum does get worn with every engagement and disengagement, and all the material goes thru the oil system. Aluminum is for minimum ET. It also means replacing it every year or two.
As for where it is and the whys... The way the geartrain works, is the sprague is the pivot point at the back of the case for first gear and reverse. There are two sets of gear sets called planetaries that are splined to various parts to get the reverse, first, and second gear ratios. In 3rd they are all coupled together for direct. One of those parts is a big cupped looking thing called the sun shell. That is splined to the forward clutch retainer. If you pull the valve body, you can see the sun shell and the 2nd gear band over the clutch drum directly over the valve body. The 2nd gear band surrounds the drum. To understand how this all comes together gets a little wordy. I'll try and be brief. You need to realize low gear when in drive, and what's called break-a-way first are not entirely the same. When the shifter is in drive and the trans is in first, the Low/Reverse band is NOT applied. This means the only thing holding the parts steady is the sprague. When the shifter is in "Low" or "1", this is known in Mopar literature as Break-a-way first. In that mode, the Low/Revers band IS engaged as a secondary holding device backing up the sprague. Manual valve bodies do not use the Low band in break-a-way first at all. Because the use of that band means 2nd gear cannot apply as fast. Which is why every box reads "Positively NOT for street use". In first gear, if the tires at any time spin faster than the engine (like letting off suddenly in first gear burnout...) or if the driveline (rear end or Ujoints) fails, the sprague alone is placed under forces it's not designed to take. Some of this can be addressed by using a bolt in sprague, but they dont address everything.. Only some of the forces. When the sprague fails as that holding role, that sintered metal forward clutch retainer (or drum) is allowed to spin at 3 times the rpms it was designed for. It explodes with enough energy to completely explode the case, floor pan, doors, roofs, drivers, and spectators.
When you hear "low band apply" manual valve body, that's the difference. The band needs time to release so inevitably they will be a slower first to second upshift. On a pure race car, totally scienced out and repeatable, this might mean as much as a 2-3 hundreths increase in ET.
This is why I said the only way to address the explosion issue is to replace the part that fails with catastrophic energy. That's the drum, and both 904s and 727s use that powdered metal drum. Most racey 904s use that steel or aluminum drum.
Sorry for the wordiness.
 
That was an excellent explanation of how these transmissions work!

The clutch drum blowing up from excessive rpm is just the last thing that happens, and is a symptom of the REAL problem, which is the sprag anchor coming loose in the back of the case, AS I UNDERSTAND IT.

Is that true?

The method by which that sprag anchor is secured to the case apparently different in the 727's and the 904's.

Having never even SEEN one, I am way ignorant and just trying to get information here. My friend, the tranny guy, says the 727s have a lot more trouble with that happening than do the 904s, and that's why they are the ones that blow up. He's been rebuilding Torqueflites for drag racing applications for 30 years, and has always attended LOTS of drag races (was Div. VII S/S Points Champ for 3 years), and says he's never seen a 904 blow up.

I have never seen ANY Torqueflite blow up, but I need to get out more...LOL!

Thanks again for that interesting and educational post, moper; that was some really good information!!!

Bill, in Conway, Arkansas
 
Thank you for all that information. Seriously it helped a lot.
 
Bill, the sprague canbe addressed with a bolt in unit, that uses 4 capscrews thru the case to reinforce the factory pressed/splined/set screwed factory part. but, it cannot addres the stamped steel fingers or rollers that can also fail simply because of brute force. So the drum is the secret to no explosions. You may still have a bad sprague, but nothing will explode, the car will just slow way down and feel very, very strange..lol. Think of it as instead of placing a trigger lock on a gun, taking out the bullets...
 
I'm currently rebuilding a 904 (with a lot of help from the guys at A & A).

The stock sprag in the 904 is riveted in, which A&A says is basically as good as a bolt-in sprag. I don't know what a 727 uses to attach their stock sprag, but its apparently not as good as either riveted or bolted.

If the sprag fails in first as previously mentioned, the drum is spun at engine RPM * first gear ratio, and if its a high stall car with a lot of torque, things are going to get ugly in a hurry. A&A says the stock drum comes apart under 10,000 RPM. Even with a 2.74 first gear, you're going to have to launch pretty high to get that to happen though.

Most peope tell me that the stock drum is ok until about 500 horsepower or so.

Steve
 
Moper said: "So the drum is the secret to no explosions."

So, the no-explosion drums need to me made of aluminum, or did you say steel was okay?

I am not sure what's available material-wise, in the aftermarket.

Thanks for the good info; I am learning a lot.

Bill
 
no, there are billet steel or aluminum drums. either is much stronger and can take any rpm the trans will reach. The factory one is sintered metal and will come apart around 8K rpm. Normally it turns at less than engine rpm. There in no horsepower reason to change it. It doesnt fail with any horsepower level. However, factory ones take 3, 4, or 5 clutch frictions. The fewer frictions, the less power it can hold. There are parts available to make any drum hold 4 or 5 clutches, and those will live behind 600, 700, or 800hp with no complaints so long as the frictions are held strongly enough, which is a function of line pressure.
 
That's more good info that I am glad to get. I appreciate the time you take to post this stuff; not many places to get this kind of information.

My friend, Len, says that main line pressure should be just enough to ensure slip-free shifts; any more than that will cost you e.t., if it's a race car application.

I know most guys like hearing the tires chirp on a 1-2 shift, but I wonder if they'd still see it as a good thing if they knew what it was costing them at the finish line?

Food for thought...
 
Len's opinion was, it was the power drain to make the shift so hard that it spins the tires that was costing the e.t., not the wheelspin, itself. I'm sure you're right though; the wheelspin couldn't have been doing anything good for the elapsed time. :angry7:

He (Len) would back the main line pressure off until it began to have a really soft shift, and then increase it in small steps until it was just satisfactory, but not harsh.
That minimized the power it took to make a sufficient amount of main-line pressure for efficient operation.

Len has won 3 Divisonal Chanpionship in Super Stock (NHRA's Div. VII), was runner-up for two others, and I have won zero, so when he talks, I listen.... LOL!
:read2:

Bill
 
abodyhotrod said:
wow buddy you must not like tci. i get it..

i was planning on the 727 but since i have a new 904 and know its lighter faster in the 1/4 i was just asking the forum for there input, thanks for yours stroked 340.
Click to expand...

hey don't hate the guy , you asked for opinions and you got one , was it not what you wanted to hear ?

Add me to the list of being a TCI hater , the street fighter is not much more than stock rebuild parts , overpriced for what you get .

Yes the 904 will be faster , but it has to be built with purpose built parts , a stock 904 will not last long .
 
Bill Dedman said:
>>>>>They have the same rear sprague and geartrain designs. Identical except in size of parts. Both will explode if the sprague is damaged and they run a stock sintered iron forward clutch drum.<<<<<

It wasn't the sprag that was the offending part; it was the way the sprag is anchored to the case that was what caused the problem in 727s, according to Len. I have never had a T-Flite apart, so I am only repeating what Len said about the problem. You, obviously have hands-on experience, which puts you miles ahead of me when discussing this issue. All I can do is repeat what he said, which basically was, the 904s don't explode because the rear sprag anchors stay put; the 727's don't, sometimes. If that's wrong, I apologize for dissemnating bad information.

>>>>>But 904s were never considered good for race cars until racers really looked into the driveline for lower ETs.<<<<<

That's true, I am sure. But, when ProTrans started building and selling their $5,000.00 race transmissions, they used the 904 exclusively, which says a lot about its power-handling capabilites, since a lot of their transmissions go into 800+ hp, 426 Hemi-powered Super Stockers.

Bill
Click to expand...

Bill it's not how the sprag is anchored in a 727 , it's the design , the new sprags available from Coan and A+A add more rollers so the typical failure of the rollers rolling over is pretty much eliminated . the 904 does have the outer cam of the rear sprag riveted to the case , not sure why that was done to the 904 and the 727 .

As far as the pro trans 5k trans , I'm pretty sure it's 904 sized components inside a 727 case and they are using STOCK 904 components , also they are rebuilding those transmissions after every event .
 
JohnRR said, "not sure why that was done to the 904 and the 727 ."

Did you mean, "not sure why that was done to the 904 and NOT the 727 ?"

I figured you did, but wanted to be sure.

Thanks for the sprag information. I'm beginning to see how this stuff happens. I think I'll stick with my 904 for now. If I ever get into some SERIOUS horsepower, I'll give a 727 some real consideration. But, I probably have all the horsepower that a 70 year-old should have at his disposal... :angry7:

Now, what did I do with that bottle of Geritol?????????????

Bill, in Conway, Arkansas
 
dear concerned i'm drag racing a 72 dart 360 ,904 trans and 8 3/4 rear 488 gears, cheata reverse manule valve body,4800 stall converter. no nos. 33x10.5x15 mickey t slicks. 1/8 mile times are 6.9 60ft time 1.46 I cant brake the little beast. the 904 is about 85 lbs lighter then 727. go with the 904 and if you need to go a little stronger go up to eather the 998 or 999 which have the same 904 guts. go for it ! Gary
 
You must log in or register to reply here.
-

Back
Top