Chrysler built
Group Name = TK 7ML


High Drum Information

High drums in A727 transmission come in several different flavors. In particular they are 3-friction, 4-friction, or 5-friction and either narrow bushing or wide bushing.

The vast majority of high drums use only three frictions. Some of the heavier duty applications used a 4-friction drum. The 5-friction drum was used ONLY behind a Hemi engine. The 3- & 4-paks are totally interchangeable as long as bushing size is considered. Because of the larger size of the 5-pak drum, a special pump assembly and special forward drum are REQUIRED to use it.

Early A727 transmissions all used a narrow (1/2" wide) bushing in this drum, while later models were upgraded to a wide (1" wide) bushing. Wide bushing drums do NOT interchange with narrow ones. If you change torque converter, pump assembly, input shaft, forward drum hub, and high drum, either bushing type will work in any A727.

The ONLY positive way to determine which drum will work in your transmission, is for you to remove the pump assembly from the transmission and measure the bushing surface length where the drum fits on the back of the pump. IF no one has ever replaced the pump body, then you may remove the converter to determine bushing size. If there is a 2" round BULGE around the vent hole at the top of the pump, then you need a later wide bushing, otherwise you need the narrow bushing. HOWEVER, THIS PART OF THE PUMP WILL FIT IN ANY A727, so it is POSSIBLE that your transmission COULD have a late type pump body and an early bushing drum or vice versa. If you order a drum using this vent criteria and it is wrong, you now own a boat anchor. To be safe, you MUST physically measure the bushing surface length.

To sum up we have the following possibilities:

Front Planets

The A727 transmission has several different types of front planets. Some interchange with each other and some don't. Unfortunately this interchangeability is VERY hard to determine accurately. Basically there are only three types of differences, 1) 3 or 4 pinions, 2) early or late gear pitch, and 3) early or late output shaft splines.

In the first case, a simple count will suffice.

The second case is a little harder, but since all planets (except for the very early 60's) are late pitch, this is usually not a problem, and if a mistake is made, is very easy to solve before re-installing the transmission.

The third case is a different ball of wax. If the wrong planet is used, the rebuilder will probably never know what happened even after the customer returns REPEATEDLY with the front planet splines stripped. Unless the rebuilder knows how to tell early splines from late, it is almost IMPOSSIBLE for him to replace the front planet in an A727 and keep the transmission from coming back to bite him REPEATEDLY unless he gets lucky. The problem arises from the fact that ALL front planets of the same count and pitch appear IDENTICAL regardless of type of splines. Not only that, but they are so close that it is also IMPOSSIBLE to measure the difference. Bottom line is that Chrysler (yes, they ARE to blame) built DIFFERENT planets that LOOK and MEASURE identically and they did NOT mark them differently in any way.

After twenty years of dealing with this problem, I know of ONLY one POSITIVE way to determine early splines from late splines. The solution stems from the facts that EARLY front planets will slip on ALL output shafts (BOTH early AND late) and that LATE front planets will ONLY slip on LATE output shafts. So, to separate early spline front planets from late spline ones, all you need to do is try all planets on an EARLY output shaft. If you don't have a KNOWN early shaft, then just keep trying planets on shafts until you have two that will not slip together. At that point you will have an EARLY shaft and a LATE planet. Mark and save the shaft, then test all planets. That should solve all of your comebacks related to the stripping of front planet splines.

To sum up we have the following possibilities:

High Drum Names

Mopar invented the high drum, designed it, produced it, and named it. TECHNICALLY the ONLY correct name for this drum is "Front Clutch Retainer," which is what Mopar named it. If you think that what YOU call it is the ONLY correct name, then YOU are welcome to your OPINION, but PLEASE do NOT try PLAYING God. No one likes being force fed YOUR OPINION. Only BULLIES (like Osama bin Laden) act that way. Just because you BELIEVE something to be correct does NOT make it correct.

Some of the CORRECT names for this drum are: High Drum, High/Reverse Drum, Front Drum (in front part of the transmission), Forward Drum (in the forward part of the transmission, not to be confused with the next drum which controls the forward MOTION of the vehicle), Kickdown Drum, Direct Drum, Reverse Drum (not to be confused with the Reverse Brake drum in the rear of the transmission), all of the above with "Clutch" inserted before "Drum," and all of the above with "Drum" replaced by "Retainer" or "Cylinder." These are just SOME of the American English names for this drum. When you take in to account that there are OVER 3000 languages and thousands more dialects on Earth, and EVERY one has or can have one or more DIFFERENT correct names for this drum, even a jackass should be able to see that it is IMPOSSIBLE for there to be ONLY one correct name for it.

Some references:
Don't you just L-O-O-O-O-VE the terminology in the transmission business???

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