727 rebuild advice

[Darn Dart]

I am getting ready to rebuild my 727 out of my Dart drag car and was wondering what kind of performance mods anyone would recommond. It already has a 5.0 lever, a low(2.77)ratio low gear set and a homemade manual valve body, that I am going to replace with a TA Cheetha manual reverse unit. I am also going to use a Kevlar Band and possibly clutches?? I have also heard a bolt in sprag is a good upgrade?? Trany guys, let me know what you think.....

[sumthin fishy]

Darn Dart, I have been racing 727's for awhile, and in my opinion the 4.2 lever is better. ( easier on the trans) and shifts just as hard. As far as the bolt-in-sprag, I wouldnt use it because if your sprag does fail, the trany really comes apart. LOTS MORE DAMAGE. and flying transmision parts. As long as you dont do any 1st gear burn-outs you'll be OK. You always have the option of a shield, if you are worried, and they are required at certain et,s

[Darn Dart]

Why don't you want to do a first gear burnout? I have heard this before but I never knew why.

[PLUM CRZY]

I keep hearing the 4.2 lever is better. Where can you get one??? Ive only seen the 2.9 levers. I wanna do a 727 with the B&M kit, one cause it has performance modification instructions and two all the perf mod parts are in the box! It cant get much easier! What do you guys think?

[Jims451]

I think the 4.2:1 lever was more common the the AMC cars that had the 727. The 3.8:1 lever also works pretty good.
Make sure to check your clutch clearances too.
I just put together a trans and I could not get the correct clutch clearance using the retaining rings that came in the transmission. I was bailed out of this problem by a good Mopar Mechanic that had a box of various thickness retaining rings at his shop.

[CUUDA]

THERE IS AN ARTICLE IN THE APRIL 2001 ISSUE OF MOPAR ACTION
CALLED "BIG BANG THEORY" THAT WILL TELL YOU ALOT OF WHAT YOU MAY WANT TO KNOW ! IT IS ON PAGE 32

MOPAR TO YA !!

[tsteiner61]

PLUM CRAZY,
TCI sells the 4.2 lever, part #146900.

S.F.,
I have to disagree about the bolt in sprag. IMO, it is in the case much more securely than the stock sprag, which is just pressed and staked, and the cam and retainer are fresh with no grooves or brinnelling which really is the major cause of a sprag failure in the first place. In fact Chilton's recommends a bolt in sprag be used at overhaul time. You are right, though, when it goes, it REALLY goes.

TCI sells the bolt in sprag as part # 127000

[transfixleo]

Ditto on skipping the 5.0. The 3.8 or 4.2 are the levers of choice. The 3.8 is readily available in a 904 case and as mentioned the 4.2 was in the AMC Torque Command version of the TF. As for the low roller, the best thing to do IMO, is to leave it alone! I mean, don't even touch it if you can avoid it. Why? Because there is wear, even if it is slight and it all is still in there working now. Once you pull it out, guess what? That is when problems start. Just spray it with some WD-40 if you run it through a washer or otherwise just oil it up and set endplays down tight to help keep things in line. I would prefer to see you use the TransGo full manual Reprogramming Kit and do first gear burnouts, just DON'T let off and get back ON again, that KILLS the roller! I also am not a fan of Kevlar unless you are a Cop and need a good vest!



To all on this board, Merry Christmas to you and yours!

[sumthin fishy]

Something else that should probably be brought up here is installing the 4 gear planitary, in place of the 3 gear. It has been discovered that some years (and I'm not sure which years) the pitch on the gears are slightly different than others, and cannot be used. they will drop in, but you can feel a bind, if you have some experience. I have run into one that would only go 1/2 way in. There have been some trans explosions that have been caused from this, that have previously been blamed on the sprag. I am guilty, as I'm sure many of you are to mix and match parts from several transmissions. If ANYONE has the dates, or any more info on this please respond.




Win if ya can,,, lose if ya must,,,but always cheat! :-)

[John Kunkel]

The planetary gear angle of helix was changed from 21.5 degrees to 22.5 degrees in '67 for noise reduction. This change was enough to prevent interchange. If a low angle planetary is inserted into a high angle annulus gear, or vice versa, it will go half way and stop. There is no way it could be assembled into a trans and, therefore, no way could cause an explosion. There were no 4 gear planetaries prior to '67 so all 4 gear units have the later 22.5 deg. gears.
I would disagree with the advice to leave the sprag intact when overhauling a trans. One of the preliminary failures of the sprag components is for the rollers to develop flat spots and proper inspection of the rollers and the outer cam require disasembly.
If you're using a manual valve body that doesn't apply the rear band in first gear (most don't) then burnouts in first gear are a NO-NO. It can lead to sprag failure and trans explosion.

[topfueldart]

does anyone know where i can learn alot about going thru a 727? or any tranny for that matter? Ive done motor work in the past and i know alot, but i dont know where to start in a tranny. Id like to learn how to rebuild them and make them stronger using sprags, clutches, bands etc. Is there a good site on tranny rebuilding? a book? Thanks,
Andrew

[71 scamp]

Darn Dart, some nostalgia super stock guys told me an aluminum drum is one of the best safety items you can put in a trans. Not quite sure why, they said it helps keeping it from blowing up.

[sumthin fishy]

John, Thanks a lot for responding, takes a load off my mind. I heard all that at the track, and did have the one that would only go in 1/2 way, so made me a believer, I appreciate this thread, and folks like you to set us straight.

Merry Christmas to you all............................
Sunthin Fishy

[transfixleo]

"I would disagree with the advice to leave the sprag intact when overhauling a trans. One of the preliminary failures of the sprag components is for the rollers to develop flat spots and proper inspection of the rollers and the outer cam require disasembly.
If you're using a manual valve body that doesn't apply the rear band in first gear (most don't) then burnouts in first gear are a NO-NO. It can lead to sprag failure and trans explosion."

I respect your opinion on this but let me elaborate on my position so others are better able to make a decision on what they will do. Agreed that if the sprag has wear on it that it must be replaced. I am going by myself and others experiences with these over the years in that we believe that you are taking a risk when you dissassemble the roller on these. The actual rollers themselves on any roller clutch are good/no-good. There is no midground as there is with a sprag that by nature, wears away. If there is a flat on the roller the roller has already fragged. There IS a very good chance though that the outer race could have a bad spot in it and you should try to check for that as best you can. The problem is there seems to be a unique failure on the TF tranny that happens when you dissassemble the roller. I know a guy that would very often experience a blown roller shortly after OH and never understood why. I finally convinced him to leave the roller alone if at all possible and his problem mysteriously went away. I rarely had this happen to me because of this practice (which you probably know as something Gil Younger teaches- {TransGo}).

As to no rear band and problems with burnouts you will notice two statements I made. One is that you must NOT let off and get back on the gas. That is what kills the roller- and probably the case too. Second, I recommend the TransGo full Manual kit which DOES use the rear band.

I want to repeat that this is simply expressing different views so others can understand our positions and not criticising the position. Merry Christmas everyone!

[John Kunkel]

I am familiar with Gil Younger's advice regarding leaving the sprag unmolested but in another bulletin he recommends grinding the ends of each roller to a taper. Is it me, or is that a paradox? How do you grind the roller when it's not removed from the case? I don't want to set myself above the "experts" but I respectfully disagree with him on this subject. I have always removed the components for cleaning/inspection and have not experienced the failures shortly after that you cite. I would chalk up any such failure to pure coincidence or poor workmanship.
Getting off and on the throttle in first gear is, indeed, hard on the sprag but so is the water burnout in first. The sprag relies on the reaction torque imposed on the gearset to firmly seat the rollers. If the tires are spinning freely in water, there is little resistance in the gearset and, therefore, less reactive torque to seat the rollers. In this situation, the inner race tends to "skid" across the rollers and wear flat spots on them, leading to eventual failure.

[transfixleo]

Part A: Not contradiction at all. If you recall he says to leave it in there but if you do take it out to chamfer the roller so as to allow it to work with the wear already there.

Part B: Agreed but again I am talking about using a VB kit (TransGo) that DOES use the rear band and as such should leave the roller ready to go. You can start in first with the tires spinning and shift up to second and the rollers are out of the equation.

[cdignition]

Why even suggest to start a burnout in 1st OR 2nd....you should start them in 3rd...with wet tires ONLY. Never dry hops, never start them in 1st...I have done hundreds of burnouts in 3rd with no damage to anything....

[Tim_K]

Here's my opinions and questions.
For improvements to third gear and reverse shift quality, use a flat (rear drum) clutch retaining snap ring in the front clutch assembly instead of the stock waved ring.
Aluminum drums may be safer, but they put out a metal powder in the oil and wear faster. Metal in the oil is not good.

For my burnouts with stock transmissions, I put the shifter in manual low to lock the rear band, which either supports or takes the load off the sprag rollers. I don't do crazy burnouts, just enough to get the tires spinning, then I let off the brake and the car rolls forward until the tires get traction and stop spinning on their own. My burnouts are never more than part throttle, that's all it needs. Shifter in manual low the whole time. This is ok, right?


transfixleo - can you give me a shift kit recommendation? Here's the setup: '74 duster, built up /6 car with a 904 and 3.55 gears. It'll be running 13's or 14's next year. It has a floor shifter, so I want a manual valve body that keeps the stock shift pattern AND applies the rear band in manual low.
Now - I've heard that some valve body kits use the kickdown linkage and some don't, even if they are full manual kits. The kickdown being hooked up is supposed to give normal feeling shifts at part throttle around town driving, while going to full throttle opens up the kickdown for hard shifts. I don't want to bang shift while cruising around, so I guess I need the kickdown setup. So, what kit will do all this for me? And will I then be ok to do burnouts in manual low only?

[sumthin fishy]

Can anybody tell me if there are any parts that are not enterchangable in the 727, say from 67 to 78? except of course for the reaction shaft support and front clutch. (piston retainer)
Thanks in advance.

[Darn Dart]

Thanks for all the great advice guys, I have a better understanding of the whole transmission now. With the TA Cheetha valve body are you saying it does not apply the band in manual low, it only uses the sprag?

[transfixleo]

Hi Tim,
I would suggest the TransGo Reprogramming Kit as it works on both the 904 and 727. It is allot more than just something to make it shift harder. It also fixes some of the more mysterious problems that have plagues TF's for years, including drainback problems and at least one of the reasons for the broken converter necks that most of us have seen. If this is a street car I would use the Auto version as it still allows you to hold any gear till any RPM so being a manual setup is not required. If you do want the full manual it still uses the TV linkage to control pressure, which is a good thing. I ould do the burnouts in Man1 but as mentioned before, get the tires wet, get 'em spinning and either upshift out of low or just let off. Do NOT blip the throttle again or you will be paying track cleanup fees!.

As far as changes I think that John Kunkel will probably have more of this at the tip of his fingers that I will. There were general changes such as the L/U or non L/U, changes in the Input shaft spline, Pump changes as well as you mentioned the drums and other subtle changes I can't think of at 5AM!

[Mr. Trans Am]

Hey Transfixleo, what do you think of putting an aluminum drum in one?

[transfixleo]

I honestly don't think that most people need that sort of thing. If you have a high revver or are looking for that last .001 then OK but you are looking at some big dollars.

[John Kunkel]

Most '67-'78 727 parts will interchange as long as their associated parts are also changed.
The front drum and reaction shaft will fit the earlier trans if changed as a pair.
In '76 the angle of the front spline on the output shaft was changed, so the front planetary gear won't interchange unless the shaft is also changed.
Valve bodies changed in '71 with the introduction of part throttle kickdown. '71-'76 VB's will work back to '66.
The rear clutch drum and Belleville spring design changed in '73. Will fit earlier units if all components are matched.
'78 saw the introduction of the lockup converter. Input shaft, reaction shaft, valve body, etc. are different. Gotta be careful here, best to not interchange parts with earlier units.

[tsteiner61]

On the subject of parts interchange, I came across something odd in my latest 727 rebuild and was wondering if anyone could identify it (year or years). It was an input shaft with the rear clutch apply hole in a completely different area than I am used to seeing on 70s models. Normally, there is a large (approx 1/4") hole between the two rings, then toward the rear clutch piston retainer, there is a sloped area. The one I saw had a 3rd ring where the sloped area is and fed through there. It wasn't compatible with the oil pump reaction shaft assembly from an early 70s model.

Was this a lockup style input shaft? It came out of a non-lockup unit, but it was a junkyard pick and you can never assume that those are in stock condition.

Just a question, because it was puzzling. Gee, no wonder I couldn't go forward.

[John Kunkel]

What you describe is the lockup setup, the third ring rides in the bore of the clutch retainer and seals the feed port to the clutch while the frontmost ring now seals the feed port for the lockup converter.
That's why I recommended against swapping parts from the lockup to the earlier units.

[tsteiner61]

I guess you learn something new every day. I learned that one the hard way. Thanks for the positive ID. Good to know next time.

[djswwg]

WOW! what an incredible amount of info-thanks everyone! In my 727 I use the B&M manual pak, which to my knowledge does apply the low gear band when in first gear. This trans was rebuilt last summer. Way to much heat (from too small a cooler) took out the front clutch pack and hurt most of the other soft parts, but NO hard parts were damaged. During the rebuild, we went to the extra high gear clutch plate, enlarged the fluid drain holes as per the B&M transkit instructions, and added the 4-gear planetary. The roller sprag was not removed and according to the Tranny man who rebuilt it, (over 20 years rebuilding them) it was as good as new. I have always done my burnouts like this. back into the water, shift into low, blip the gas pedal to wet the slicks, roll ahead 2 feet and smack the throttle. The revs come up real quick and around 4500 I hit second gear, then when it climbs back up to about 5000 I hit 3rd. By this time the slicks are trying to pull the rpms down so I deep throttle a bit more to keep her at 5000 or so. After the smoke is really rolling, (about 5-10 seconds or so), I take my thumb off the line lock and let the slicks spin across the starting line, (still in 3rd). Then I just let off the gas, stop and back up to stage. So why am I saying all this? Cause I want to know, is there a better way-read easier on tranny/driveline- to do a burn out, or is this what most of you guys are doing? Thanks again......djs

[Billydelrio]

djswwg That sounds like a ginuine tire smokin burnout that is similar to most others I have seen. I don't ever try to burn across the line as it is beyond the reach of my car's power. I start in 1st, shift to 2nd, and then shift to 3rd. When the tires pull, I release the lock and ease off the gas. My entire burnout takes about four seconds and three feet of track. I then puttputt to the stage. My 273 can't keep them slicks spinning long enough to cross the line! Some of them BB rails and alterds go past the 60 ft cone with their burnout pass. The amount of burnout depends on power, weight, traction, etc...

It seems to me that up-shifting during a burnout is harmless to the transmission.

Two different concerns related to the "sprag problem" as I see it.
1. The rpm that the 1-2 shift takes place as well as the 2nd gear band apply rate determines the "relaxation event" of the sprag. An instant relaxation event of the sprag will slam the springs and fatigue them. This will eventually lead to failed springs, which allows sprag slippage and front drum overspin(explosion). Some folks say not to do a 1-2 shift when the tires are spinning because it allows for too quick of a "relaxation event" on the sprag.

2. The "instant sprag apply" is the other concern. If the sprag is applied too hard, the rollers wedge too hard and things start to crack. This also allows the sprag to slip and thus allowing front drum overspin. The hard apply takes place when there is an inertia spike on the low/reverse drum. Some folks say this takes place when spinning tires grab while in 1st gear, or when spinning tires grab, causing an automatic shift back into 1st under high rpm/torque loads.

Billy

[djswwg]

Billy, sounds like the key is to make sure all the shifting is done before the slicks get real hot and sticky, which is what I do. Thanks for the input!.......djs