Can someone confirm which tranny solenoid controls 2-3 shift?

[CADiesel]

Hey ya'll, I just bought an 08 F250 6.4L regular cab 4x4, automatic, that was bone stock with 65,000 miles. I noticed that even when bone stock, the 2-3 shift was not quite as smooth as the 1-2 or 3-4. From reading the forums, it seems that this is somewhat (?) common, even when these trucks are new. Now that I have the dpf delete, S&B intake, and IDP tune (I'm running Xtreme X engine tune and Firm Shift Delay Lock trans tune), the 2-3 shift is definitely not smooth. Kinda shudders or stumbles very noticeably into 3rd under WOT. Around town, light driving, if I'm not hard into boost, the 2-3 shift is totally normal. But the more throttle I give it, the rougher the shift. What I notice is, the 2-3 shift is VERY close to the 1-2 under WOT. It's like, almost immediately after the 1-2 shift, the 2-3 shift happens out of nowhere, then there is a relatively long wait for the 3-4. FWIW, the 1-2 and 3-4 shifts are firm, but totally normal...

Not wanting to invest too much money into this thing in case the trans needs internals, I pulled the pan and removed the intermediate solenoid (SSPC-C in the diagram below), and the reverse solenoid, thoroughly cleaned both with carb spray and compressed air, and swapped them. I figure it was better to have a shift "stumble" into reverse than into 3rd. I thoroughly cleaned the pan, installed a new Motorcraft trans filter, topped off fluid with Mercon SP from the dealer, and went for a drive. The stumble is somewhat better (might just be from 8 qts of fresh fluid), but not totally fixed. It's really evident because all other shifts are firm and nice. Since there wasn't hardly anything gritty at the bottom of the pan, I'm going to possibly conclude that the clutches aren't thrashed, and that the issue lies in one of the other solenoids that also affects the 2-3 shift. Can anyone shed any light on what other solenoids affect the 2-3?

[senix]

Perhaps Mark K will chime in when he sees it. He was in on the engineering of this trans.

[Mark Kovalsky]

The 2-3 shift is a swap shift. It's a unique type of special shift.

The TorqShift is really two transmissions in one case. There is a two speed in the front, with ratios of 1:1 and 0.71:1. The 0.71:1 ratio is commonly called overdrive. The rear transmission is a three speed.

Here's how the trans shifts:
1-2 The two speed shifts from 1:1 to 0.71:1, the three speed remains in first gear.
2-3 The two speed shifts from 0.71:1 to 1:1, the three speed shifts from first to second.
3-4 (really 5, 4 isn't used except in special cases) the two speed stays in 1:1, the three speed shifts from 2-3.
5-6 The two speed shifts from 1:1 to 0.71:1, the three speed stays in third.

Since there is an upshift and a downshift going on at the same time the 2-3 shift will NEVER be as good as any other shift in the trans. Those two shifts (upshift and downshift) have to complete within 0.030 seconds of each other or you get some nasty shift feel.

So for the 2-3 the transmission downshifts the front unit using the overdrive solenoid and upshifts the rear unit using the intermediate solenoid. That's the long way of saying the overdrive and intermediate solenoids combine to make the 2-3 shift.

[foreman1063]

Interesting, thanks for sharing.

[jimmy]

I never bothered to study on this before. I thought something more "special" occurred in the 5 spd torqshift.
SO it is really a 4 speed with OD top gear but with careful selection of planetary ratios you slide an extra gear through use of the OD in a lower gear range. Nice.
It looks like the 6 speed uses a Ravigneaux planetary to get the 6 ratios.

[Mark Kovalsky]

No, it is really a three speed that uses the overdrive gearset to create three additional ratios. The first additional ratio is second gear (2.2:1.) The next additional ratio is fourth gear (1.09:1.). This gear is only used below 0 F and during certain kickdowns from sixth gear. The last additional ratio is sixth gear, commonly called overdrive (0.71:1.)

[CADiesel]

Very interesting and informative, thank you Mark and others for posting! So I'm going to just live with it? However, what are everyone's thoughts on some of the modified "direct drive" solenoids such as the one from Go-Go Diesel? Just with the Innovative trans tune, the 1-2 and 3-5 shifts are firm, yet not overly harsh, but I've read guys who say the shifts are brutal with the Go-Go solenoid combined with aftermarket trans tuning. If there is some way to improve the 2-3 shift I will certainly do what I have to, otherwise I will leave it and enjoy the truck.

[senix]

I think if I were looking for a fix of some kind then what about just some trans tuning in the form of an aftermarket TCM?

Is that a possiblity? Is that something that is even out there?

[Mark Kovalsky]

I've never heard of an aftermarket TCM, that would be rather hard to do since the TCM is in the same box as the ECM. There are many aftermarket tuners that also tune the trans. Can they do a better job tuning it than I did? We'll see.

[CADiesel]

So I'm guessing that because the 2-3 shift also involves a downshift .030 seconds later, the "stumble" is probably a magnification of normal 5R110 behavior, that is more noticeable because of increased line pressure brought about by the aftermarket trans tuning?

[Mark Kovalsky]

If the downshift is later than the upshift the shift is going to feel awful. Both the up and down shifts need to happen at the same time and end within 0.030 seconds of each other.

I have no idea what the aftermarket tuning does to the shift. I spent hundreds of hours working on just that shift. Just adding line pressure would probably magnify any bad feel.

[jimmy]

Thank you Mark. Your work on the 5R110 is great. I have had mys expectations exceeded on this transmission.
It's the people behind too few head bolts on the engine who are a classic fail.

[Mark Kovalsky]

International was a fail on that engine from the start. We had problems developing the transmission because we needed to be able to drive the trucks. The engines often prevented that. On one memorable cold weather trip we had three of six trucks DOA after the first day. Two of them never ran.

[senix]

Originally Posted by jimmy

Thank you Mark. Your work on the 5R110 is great. I have had mys expectations exceeded on this transmission.
It's the people behind too few head bolts on the engine who are a classic fail.

I agree it is an excellent dependable tranny..far better imho then the new one out for the 2011 and ups

[Mark Kovalsky]

The first prototype of the six speed TorqShift (the current transmission) was assembled on my last day at the Ford Motor Company. I didn't bother going over to the build up area to see it.