Twitch,

The 'Type F' argument has been going on for years now. It's ironic that aftermarket 'performance' transmission fluids, like that marketed by B&M, is based on the Ford Specification. B&M also provides this fluid with the GM 700 R4 Hydramatic which calls for Dexron-Mercon as a factory fluid.

MBZ changed the frictional properties of the bands in the 722.120 transmission sometime around 1980 to give a 'softer' shift, based on customer complaints. However, keep in mind that a crisp, instant shift, promotes clutch and band longevity because it reduces 'flare' and the subsequent heat of slippage.

When I serviced my 722.120, I used the ATSG Manual, which was fairly decent.

I made no modifications other than adding (6) springs to the Direct Clutch Piston. You will notice a number of small 'pins' in the piston onto which a small spring is placed. In most 722.120's there are (12) springs, but there are enough pins for (18) if I recall correctly.

I believe these were omitted by MBZ over the years to make a softer shift.

Basically, I have several transmissions for parts and I placed a spring on every pin. This requires more pressure to overcome the springs and gives amuch crisper shift into direct (4th) speed

What I also did was take the time to reduce the clearance in both clutch packs to the minimum specification by utilizing the selective fit steel plates. I also took great pains to get the proper band adjustment. This pays some real performance dividends when the unit is properly built.

The planetary units in the 722.120 would be at home in a 2.5 ton truck. They are larger than the GM 400 Hydramatic and even the modern GM 4L80-E Transmission. Hard parts and bushings seem to last forever in this unit.

There are two major problems I have found while working on these transmissions. The first is Direct Clutch Failure which is brought on by lowering modulator pressure (backing out the modulator adjustment) to satisfy the customer who complains of a hard or suddent shift.

The faster, more immediate the shift is, the less heat and 'slippage' the friction elements are exposed to. You don't want the shift to 'jerk' but it should give no indication it is about to take place either.

The next problem is Direct Clutch Failure (3-4 shift flare or slip) brought on by low vacuum from leaks in the system, depriving the vacuum modulator of proper signal.

You should have relatively high vacuum signal at the modulator valve on top the injection pump, around 10 to 12 in/Hg. The vacuum should diminish gradually as the throttle is opened to around 2 in/Hg or 0 in/Hg as full throttle is reached.

What I did on my 116.120 to minimize this proplem is chang the vacuum routing to make the modulator the first item in the vacuum circuit. I installed a 'T' fitting with a one-way check valve on the line coming off the vacuum pump.

In this way, vacuum goes to the shift modulation system (the plastic valve on top the injection pump and the actual modulator on the transmission itself) before anything else receives a vacuum signal.

The one-way check valve is positioned downstream of the modulator valve so vacuum is maintained after shutoff. Keep in mind the modulator valve on top the injection pump is a controlled bleed, so a small amount of vacuum is lost through it all the time.

I then increase modulator pressure (clockwise) until the shifts 'feel' good and crisp, but are not harsh. I have found this is more of a trial-and-error effort than a specific adjustment.

However, I have personally seen these 722.120's with over 500,000 miles that still looked good on disassembly. When I opened the one in my Dad's old 300 D with 475,000 miles on it, the MBZ Star could still be seen on the friction elements and the bands.

The only reason we pulled it was because of external leaks resulting from hardened rubber seals. Dad didn't want to spend the $175.00 on the overhaul kit that contained the (8) clutch plates, so we just replaced the rubber seals

I hope this information is helpful...bert