Zamorush,
The main point of not wanting to allow the car to change up to D or 4th ratio at slow speeds has been covered in detail in some of these threads, particularly by Harvey, ob-au, you can search his posts.
Because the final drive is so high, 3.53 as Phil corrects me, and because 4th is a very high overdrive at 0.694, this means if the car is travelling at slow speeds with 4 engaged, the engine is only turning over at 1500 rpm +. This is very restful in a "cruising" sense, but puts high torque loads on the internals, and also, the pump oil pressure in the box is not up to maximum because the revs are too low.
Line pressure being too low means the brake band which operates on 2 and 4 may not have sufficient grip to avoid slippage. Most of the people who have replaced/rebuilt ther trannies first notice the wear as a "flare" on 2.
The shift map causes the box to seek 4 at about 45, and will slip the TC rather than drop to 3 unless you make it kick-down or get POWER engaged. This puts heat and torque loads on the tranny.
These loads are a contributary factor in the recurring tranny failures. If the final drive was lower, say 4.11, then possibly the current shift map would work very well, this is discussed in another thread.
Joe
