When is a Race trans not a race trans....

Before I start, the subject question is rhetorical....but....

A few mths ago I got talked into buying a “Race” 727 with rmvb from a well known commercial trans company.

I wanted to go with CRT....but international shipping was just too much with our dollar so ended up going to a local retailer and buying a RMVB from CRT and billet servos from a seller on here.


Unfo my upgrade strategy didn’t go far enough....

A guy I know just had an issue with his “race’ trans, and on inspection, we found a lot of ‘heavy duty’ components simply weren’t included....which is kind of surprising as the company claims the trans is good for 800+ HP.

ANYHOW...my question is this.

If I change to a low band apply RMVB....how important is a bolt in sprag?

The motor will be making around 500hp at 3700lbs.

Broken Arrow.

Yep...that means a lot! :lol:

A bolt in sprag is nothing more than a stock
sparg.. they are used when a sprag has spun
in the case and a stock one is put in.. A
super sprag has many more rollers and is much
less likely to blow.. you can pull the VB and
use a stock one

Hi Mr P

I don’t know a lot about trans, I guess what I’m trying to pin down is - Does a low band apply VB take the risk out of spinning the sprag?

LBA takes a lot of load off the sprag but sprag failures have been known to happen even with Super Sprags and LBA. At you HP level it's less likely.

There is no universal agreement on what constitutes a "race trans", some of us believe that a lot of the "race" components are just glitter....nice if you want to spend the money but not needed at some power levels.

I would invest in an alum or steel billet front drum

The only thing that take the entire risk out is a good high gear drum. That being said I've seen transmissions roll the sprag with LBA and stay together. My trans just busted up a Super Sprag (non LBA). It was no fault of the sprag itself (the output shaft roller bearing failed). The trans still functioned perfectly. In fact it went 1.25 60ft on its last pass. I've even seen Super Sprags break after axle failure. I ran stock drums and sprags forever. Never hurt a stocker. As far as power level the stock planets (foot brake) , clutches, shafts have all survived easily at well over 800. I'd suggest a steel carrier front planet if you run a trans brake.
Doug

Hey Mal.

Just went through this with my 904. Said trans was built by a Sydney Chrysler
guru but when i found excessive band material in the filter the line given was "Its the filter doing it's job" Anyway turns out the rear band was shot and the rear clutches were burnt after 6 street meets and a 1k's

If you have the tools build it yourself or buy the bits and have some one local piece it together. You could try Pro trans or BBE automatics. Its not rocket science.

Hi again

Thks for the input. I have a really good local trans builder, just wasn’t sure what to swap out and what to keep.

I have a CRT rmvb that’s going in and billet servos - But I think I’m going to swap out the sprag.

I’m disappointed in this TCI Drag trans, has no bolt in sprag, no re-enforced front strut, only 3 pinion planetaries and no billet drum - I should have just paid the extra shipping and gone with another CRT.

A standard 727 properly assembled without any tricks, will easily handle your power and vehicle weight. The billet front clutch retainer will keep you from getting hurt and breaking the case if you have a driveline issue.

Take a look at an old Direct Connection catalog which shows “race” transmissions available.
These were new, production transmissions built at the transmission plant, using production parts. No bolt in ORC, billet drums, etc.

The problem that I have seen repeatedly is the builders ability to know what is good and what is questionable when reclaiming some of the parts.

Another reason why some builders insist on using new drums, planetaries, etc.
If it fails they can blame the supplier of the part while taking the risk out of the equation.

This same mentality is seen in some dealer repairs,

Not criticising, just stating some findings and facts.

I take your point, but some parts provide insurance against accidental abuse.

I guess I just assumed a ‘drag race’ transmission would at least have a bolt in sprag -

I wasn’t expecting a billet drum or servos, (although CRT do priovide a billet servo in their race model...so not sure why TCI can’t?)

Buit with the motor rebuild nudging 500fw....I want to at least make sure noted weak links are fireproofed.

I wouldn't lose any sleep over 3 pin planetaries. The aluminum spline will fail before a pinion will.

My trans guy used to remove 2 pinions on a 4 pin on his SS Hemi car. Never broke a pinion but spun the splines out of a few.

Kevin

How many rpm are you planning on

6700. Launches around 2500. Converter flashes to 3600.

I was gonna tell you if the RPM was low enough
(below about 6300) you wouldnt have anything
at all to worry about.. RPM is what causes drum
failures.. IF the ORC fails that lets the drum
to spin 2.2 times the engine rpm..drums have
have been spun(used old drums)and they tend to
fail at right about 13K rpm which is close to
6,000 rpm but giving a cushion.. I have been
running a stock drum from day 1.. if you dont
do stupid stuff you dont have a issue.. I've
been turning my engines to about 8100 and some
as high as 9600rpm(not often to 9600).. that
was a test

I would rather SPEND DA BUCKS on a good drum than CHANCE blowing up a trans ... losing the case .... destroying the valve body and MAYBE hurting the converter !!

A local high dollar racer had his engine, tranny builder cut some corners on a trans brake 727 which ended up exploding the front drum, came through the floorboards setting his driving pants on fire and hurting his left foot
A steel drum or a aluminum drum with steel liner or a all aluminum front drum will insure that you won't explode it

Mal,
Sorry to see/ hear your results .
Lets just say i heard once what TCI means but i have not used them so thats not for me to say .
Here is a couple of my thoughts , as i am in Aus just like you . And i have built,worked in auto shops .
I have a foot brake B&M . Cracked old case and no BB core .
I ended up with a Griner RMVB . This trans ran 10.50s behind my 505 . It ran about 9 years with only regular servicing . Only broke 2 front flex bands , swapped to solid band solved that . No other issues. Still on my shelf for a spare .
Current trans has a brake and has gone 10.20s off the brake @4000 trapping just over 7000
This has a billet drum and is set for racing , though i daily drive it . And yes i paid $ for it , similar to importing a CRT .
Both trans have low band apply to help .
Fred @ Protrans here in Sydney built it .
I rang B&M when choosing theirs and they said 600hp is the round about limit as delivered .
I guess its all a pick and a poke . Who will look after you ?

Tex

Gday Tex.

So what is the story? I have a Griner/Cope RMVB to swap in.

Where I’m stuck is the d3cision on the sprag and 2/3 strut...I think the bolt in sprag is a must...haven’t heard much about struts failing.

The bolt in sprag, as others have said, is not necessary. The only reason I would use one is if the stock sprag was loose in the case or had obvious problems.

I tyically build 4-5 727's a year for local guys and never have an issue there.

The 727 in my car holds well over 700HP on spray and it is surprisingly stock! LBA Turbo Action fwd pattern valvebody, good clutches and steels and governor removed (not necessary, but just less parts to fail if removed.)

Which brand(s) have you used and why?

I have been racing mopars since 1974, never had a trans blowup or even burn one up, knock on wood. Always built my own. I have seen several of my buddies blow up over the years, lucky only minor injuries. With the damage possible to car and humans, it is only smart to use a good drum. I like the aluminum drum with the stainless sleeve, good friction surface and lightweight. The problem is most valvebodies do not hold the rear band in low gear, that plus the stress of not doing a burn out right is what causes the issue of sprag failure. I have used the low band apply valvebody, because it is safer, but in my testing the regular manual valvebody, that does not hold the band is a little faster. The low band was just not designed to be released quickly. Which is what you need for a clean 1-2 shift. Even with the modified low servo, just my opinion.


http://www.tcsproducts.com/media/1/TCS_TF727_Performance_Transmission_Parts.pdf

Correct me if I’m wrong but isnt the low band applied in all forward gears if you have LBA valve body. The 1-2 shift has the kickdown band apply with no change to the rear band. The 2-3 shift releases the kickdown band and applies the front clutches?

No. It releases on the 1-2 upshift.

You can weld a small piece on the strut to reinforce it at no cost. The standard bolt in sprag does nothing. It to repair a damaged case, nothing more.
Doug

Ok thanks!

If building a big sprag will not hurt , strut bar yes a heavy duty or billet one us good
Low band apply only way to go especially street driven
If you are starting from scratch and are seriouslly racing put a billet drum in . Though my footbrake trans has a stock drum , it was 65/6600 throuh the traps

Tex

DVW - Thx for clearing that up. Maybe I’m being paranoid, but my buddy cocked a roller in his sprag by simply jumping on-off and then on the throttle again. (Car got loose on him in the street)

Tex - I have a LBA valve body from CRT so an exploding drum is not my concern - a spinning sprag or busted rollers is....simply because of repair costs.

Mal,
Sprag failure is a bit luck of the draw in my opinion .
High HP and or high rpm needs a drum .
Make your own call after adking and thinking . Then hang on for the ride

Tex

As usual Doug’s info is spot on.... personally my $.02 is that if the car is going to see a track, put the good drum in it!

Adding a bolt-in over-running clutch adds to the prevention of turning in the case should the situation arise in my opinion. The 4 bolts add to anti-rotation protection over a set screw, aluminum interference and staking. And right or wrong I always use an aluminum front drum in a race build.

....actually a bolted in aftermarket “super sprag” can take the case out if it fails. Just some forces involved there that you can’t do a lot about when mayhem sets in.

dont let this happen

And contrary to popular belief, it doesn't take big horsepower to do that. If the sprag/overrunning clutch fails, a stone stock 318 is capable of causing that kind of carnage.

A drum explosion is strictly a product of RPM x first gear ratio, 2.45.

Kevin

I saw one let go in a 340 Barracuda dialed 13:70, so yes, it can happen to anyone.

^ Yep

.....and least we forget - TEARING UP the floor of the car and even the dashboard !!

NOT TO MENTION possible personal injury to your feet !!!

Currently putting together a 1966 727. More HD than race, the Super Sprag and Billet drum are out of the budget.
Changes so far have been replacing the 19-spline input shaft with a 24-spline input shaft so torque converter choice is easier. Rear vent, and sprag lube hole from the cooler return. Threaded restrictor plug in case. FT-2 Shift Kit using the stock '66 servos, stock 3.8:1 band lever.
Have an old rebuild kit where all the clutches were supposed to be Alto red eagles, but bulkpart shipped alto read eagle rear clutches and Raybestos Green (High Energy) front clutches. Kolene steels for both clutch packs.
The trans looked pretty good and stock with maybe one rebuild (low mileage car.) No stripped threads in the case, sprag still tight in the case, but previous rebuilder had many of the sprag roller springs installed backwards. Might install a later dual "O"-ring rear band pin.
Haven't decided on bands yet. The stock bands look fine and thinking of reusing them, but I have a new Mopar Performance Front band on the shelf. I think it is Kevlar? Not sure if I should install it or not.
Need to still get a trans cooler and maybe a deep pan.

This is the exact setup I do for guys that want a good street/strip trans. In addition, we usually add the governor of their choice if they want to leave it in drive and have it shift on its own at a desired rpm. I ALWAYS tell them to shift into 2nd during a burnout and to let me tear it down if they break a driveline component to check the sprag.

I have used both stock bands and rebuilder bands with zero issues.

I add RTV over the rear band pin depression at the outside of the case. never had one leak. If the old rear band looks good use it. I like the hard Red band best. I'd use the Mopar one you have.

You can buy more Altos here, $6.80 each. In fact they carry near everything you might need.
https://www.transpartsonline.com/TRANS_P...nsPartsType=727

But I've found the greens to hold up at 700Hp with no issue. Cant beat the 518 OD truck pan. free ship from Amazon, $39
https://www.amazon.com/gp/product/B00PH4...d=ATVPDKIKX0DER

Doug

Thx everyone for the advice. I have one last dumb question -

IF, I run a Super Sprag and a LBA valve body, is there any chance of the drum still over-running and exploding? .....or will these two items fix the risk?

Yes

Tex

The only way to eliminate the risk is buy the good drum. About the same cost as a LBA valve body and Super Sprag anyway.
Doug

I think the separation of views is coming down to HOW a drum explosion may occur.

Ruling out the common cause of no LBA valve body causing an over-running clutch.....I think I’m right in assuming only some form of drivetrain breakage would cause similar trauma.

I’m prepared to bank on no major breakages at my power level - so hopefully the LBA VB and the Super Sprag will be enough fire proofing

F this thinking is flawed...have at it

You don’t have to have driveline breakage to fail the ORC.

As mentioned, the stock drum is the real issue, the part that can explode. The Super sprag and LBA are improvements to help prevent the overspeed condition.

Link to TCS Drum tests:
http://www.tcsproducts.com/media/uploads/user-files/Drum_Tests_Jan_2017.pdf

Wow! Page 3 and the “I been runnng the stock drum 4ever and if you do everything right it won’t fail” crowd hasn’t chimed in!

Having been around two of these failures over the years (both started with broken 8.75 gear), you REALLY don’t want this to happen. One occurrence was full tilt catastrophic with peices stuck in the door panels and wiped out all the gauges + dents in the roof (he limped away luckily). This was in the early 90’s and we had NO clue that this could even occur. Our stuff got the good drum in the 727, and we put blankets on both of our cars.... even the 904.

....and speaking of 904, much smaller mass and they don’t explode. Not saying it’s not impossible, but to date I’ve never heard of one that has.

On the race trans stuff, I though the TF-2 shift kit (or was it the B&M Trans pack?) used to include the HD front band strut? Was looking through the TF2 kit and no band strut, so ordered up one of the nice thick band struts this morning.

I've been using the TF-2 kits for over 25 years and never had one come with a HD band strut, so it must have been the B&M.

Who has ever bent a band strut?
Doug

Me. Never seen one in person either. (only pics)

Not personally in roughly 50 builds, for customers and myself since 1977. I'm not betting my reputation against it, though, for basically peanuts.

After all these years, there's just no reason for anyone to be exploding a transmission. But...people still do, just like they still stick their foot under a mower, touch a stove to see if it's hot and blow their fingers off with fireworks.

5500-6000 engine RPM with a broken roller clutch is all it takes. Lower horsepower applications can get by with a non-LBA valvebody, IF you drive the car correctly. At higher power levels, you have to apply that band to give the roller clutch some help. And you have to maintain the thing - take it apart once in a while and look at it - instead of running it till it quits. In any race style application, not putting a good drum in the thing is asinine.

Well I guess I'm insane.. been running the stock
drum since the 80s.. yeah I've tore it apart a
few times for worn parts but NEVER blew it up..
no LBA.. dont pedal it in LOW.. SHIFT
it.. they only blow in low gear so
get out of low as soon as you can

If I have an LBA valve body, AND a Super Sprag, how can the drum explode?

This is what I’m not getting

2 things here.. the LBA wont stop it fast enough
and the super sprag isnt a save all.. it helps
but it doesnt help all.. if you get on and off
the gas the rollers go back then slam forward
and tighten up to tight for the sprag and starts
to come apart
EDIT
there is 3 ways to not have a explosion.. 1
is dont pedal the car under load.. 2 is buy a
drum(alum or steel or 3.. put a 904 in it

4. Scattershield and put an 833 in it. Or a Jerico, a Lenco...

Chances are it won't, unless the rear band fails to apply due to broken parts (servo, band, etc.) AND the roller clutch has also failed due to driver error, parts failure, AND you have your foot in it causing the engine to free rev to 6000+. You have to decide if you want to trust that all of that won't happen at the same time.

Ok, thx for the explanation, I get it now.

Both Dizuster and I have failed roller clutches. His with LBA. We realized it was shuddering in low gear took it apart. Rollers were were wedged and twisted, many laid over 90 degrees. Nothing was damaged but the low roller. Mine has a Super sprag with non LBA valve body. It was recently disassembled for maintenance. The rear roller support bearing had lost it's press and slid out of the governor support. Being the rear drum has been converted to roller bearing, the drum is no longer piloted on the rear support. It pilots on the output shaft. This allowed the output shaft to wander around breaking a few tabs, half the springs and laying the rollers over at about a 20 degree angle. If it hadn't been removed for maintenance it wouldn't have been caught. Car worked perfect. Ran 1.25 60ft last two passes. Both cars have good drums.
Doug

You can have a failed roller clutch that will function well enough to get the car to the lanes and to the starting line (always start the burnout in 2nd). Then when you hit it, it fails completely, usually at full throttle. Happened to me long ago, with a 904 thankfully.