Trying to clarify facts about the 5r110 tranny

[R2millers]

Reviewing this section and some earlier posts about potentially trying to use all 6 gears of a 5r110 tranny, Mark Kowaski, a former Ford engineer who helped design and develop this transmission regularly posts on the FTE forum- 6.0l Powerstroke section.

Here's one of his posting to help clarify why the 5r110 only uses basically 5 gears, not 6. If you have a tuner or scanner, you might see it downshift to 4th gear under the right conditions, even in warm weather but very rare to get a glimpse. You will also see the ratio difference between the two gears is 1:1.09 vs 1:1, so negligible and unnoticeable for us users. Enjoy.

"Originally Posted by Mark Kovalsky View Post
The extra fourth gear is a by product of the design.

The trans is a two speed in front of a three speed.

First gear is both sets in first gear. (1:1 time 3.11:1 = 3.11:1)
Second is the front upshifted and the rear still in first.(0.71:1 times 3.11:1 = 2.2:1)
Third is the front back in low and the rear in second. (1:1 times 1.54:1 = 1.54:1)
Fourth is the front in high and the rear still in second. This is the one used when cold. (0.71:1 times 1.54:1 = 1.09:1)
Fifth is the front in low and the rear in third. This is 1:1 on both sets.
Sixth is the front in high and the rear in third. (0.71:1 times 1:1 = 0.71:1)

Fourth is used cold because it was easier to get the trans to do this shift in extreme cold. The 3-5 shift didn't work very well cold, so this was the best way to make the trans work when cold. It stops using fourth when the trans is above 0F, so it doesn't stay in this mode very long."