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Discussion Starter #1 (Edited)


The forward clutch wave plates mentioned in the 'Transmission 101 thesis' are only for '96 and later forward clutch drums. They will not properly fit the old style drums unless you omit a clutch plate set - even with the thinnest snap rings available.
It is not recommended to omit any clutch plate sets, thus you are limited to the .039". 5 wave style plate with the older drums.

The '96 and later style drum has an increased distance from the piston to the snap ring groove which will accomodate these thicker plates. Not only are the new style plates made of a thicker material, but the amount of 'wave' in each plate is increased as well - making them substantially thicker than the old style .039" plate.

Please also note the earlier mention of the pressure plates being different as well.
The plate mentioned in the article will not properly fit the older style drum.
The part number for the clutch pack upgrade pressure plate for the pre-'96 drums is listed in Potential Additions/Modifications - Part 1.


For those of you who are considering a rebuild or modification of your 4R70W transmission, here are a few additional points to watch for:

Pressure Regulator Valve and Boost Sleeve

While you have your valve body off, or when rebuilding your transmission, it pays to carefully inspect the Pressure Regulator Valve and Boost Valve/Sleeve.

If you have a 1991-1995 transmission, these parts are notorious wear items, and can cause damage to the valve body, EPC boost oil leakage resulting in low line rise pressure, and extremely high pressure in reverse resulting in case and parts breakage in extreme wear cases.

Remove the main valve from the valve body and inspect carefully for wear. The valve spool typically wears severely only on one side. If not in perfect condition, inspect the valve body bore for wear as well. AFAIK, Ford does not sell the part separately, but an improved radially grooved and hardened valve is available from Sonnax - Part # 76948-01.

Carefully inspect the boost sleeve and valve for wear as well, and replace if worn.
Sonnax Part # 76948-02K.

Some units included a small return spring on the boost valve, newer models eliminated the spring. It may be left out of all applications if desired.

The '96 and later valve bodies were modified by Ford to reduce/eliminate this problem, and this valve should NOT be used.

TCC Bypass Clutch Control Sleeve and Plunger Valve

To correct notorious problems with '91-'95 4R70W torque converter shudder and to quicken and firm the TCC apply, an improved upgrade TCC Bypass Clutch Control Sleeve and Plunger Valve is available. Sonnax Part # 76948-04K.

Probably not needed/recommended on '96 and later valve bodies.


You can identify the model year of your valve body by the alignment pin bolts and pressure regulator valve design.

The older pre-'96 bolts have 13mm heads and no step on the pressure regulator #3 spool.

The improved '96 and later valve bodies have alignment pins bolts with 10mm heads, and the pressure regulator valve is of a stepped design on spool #3.

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