how many springs in the 727 front clutch?

Hi Everyone!

By the sounds of things my 727 rebuild kit should be here tomorrow, which likely means
I'll be doing some tranny work over the weekend. One question that popped into my mind
was with regards to the number of springs in the front clutch drum. Stock, the 727 has 9
springs, I've heard that increasing the number of springs will produce a firmer clutch
engagement? Would this be of benefit when trying to firm up the shift?

My '80 FSM says almost all the '71-'79 727s used 9 springs with the exception of the
440-6 and the 426, which used 12 springs. Those 2 setups however also used 5 front
clutch plates and discs.

Any hints or experiences?

Thanks as always!

-Dariusz

As per Mopar Chassis 8th edition. The 225 cid had 3 plates and discs, .036-.086" plate clearance and 12 springs. The 318cid had the same. The 340-360 used 4 plates and discs, .024-.125" plate clearance and 6 springs. The 383-400cid. used 4 plates and discs, same clearance as the last and 8 springs. The high perf. 383-400 had the same specs but only 6 springs. The 440 high perf. used 4 plates and discs, .066-.123" plate clearance and 10 springs. The 426cid used 5 plates and discs, .022-.079" plate clearance and 12 springs. I do not know anything about front clutches but I thought I would share my book if maybe it could help.

[PLUM_72]

This is an ANCIENT post, but I have a similar question. How many springs should be used in a 727 front clutch? From the different posts, it seems like 12 is the magic number. Opinions?

[PLUM_72]

btt

[John Kunkel]

The factory used a variety of different spring combos on the same motor in different years and the aftermarket builders won't even agree on the best combo. To add to the confusion, there is a long and short front clutch return spring and their tension is different at installed height. (The short spring is the stiffest) So, ten longs have the same tension as seven shorts, etc.

The theory behind a strong front clutch spring pack is to slow down the engagement of the front clutch during the 2-3 upshift, this should prevent the severe overlap that occurs if the clutch applies firmly before the kickdown band is released. If the clutch engagement is slowed down too much, there will be engine rpm flareup as the band releases and there is no clutch application. One downside to a stiff spring pack is reduced holding pressure at the clutch. Higher pressures can overcome this but higher pressures lead to quicker apply times, a vicious circle.

The front clutch spring pack and clutch clearance should work in concert with the kickdown servo and band lever ratio for the most efficient 2-3 upshift overlap.

Confusing??? You betcha.

My personal preference is to run a fairly loose four disc front clutch pack (.060"-.080") for minimal drag and best lube flow, combined with a medium spring pack of nine short springs. The apply rate of the clutch can then be controlled with a simple orifice restrictor in the front clutch apply passage. Most reprogramming kits supply a small cup soft plug with a drilled orifice that is driven into the passage in the case. I prefer to tap the case 1/8" NPT and install a socket head pipe plug drilled to the appropriate size (I start at .150"), this is easier to remove and change.

The orifice offers the advantage of being easy to change by merely removing the valve body, clutch changes require removal/disassembly of the whole trans.

[mhenesian]

I'm reading this 11 years after John Kunkel produced this very excellent discussion. I'm trying to decide on the number (and length) of springs for the front clutch pack in the A727B that I'm rebuilding for our '69 Plymouth bracket machine that my son and I race at Sonoma Raceway. If John is reading this we wish him good health ! Thanks John for your tremendously informative posts over the years. Mark and Stephen Henesian

[John Kunkel]

For drag cars the current favored trend is to run the full 15 short springs with .015" clearance per disc, this takes advantage of the current higher pressure valve bodies.