Allison Transmission (HT-740) Washer retainer.

[chris19a]

Hello,
i just opened my ht-740 oil pan and found this broken washer retainer.
Does anybody knows where it came?
I looked to the service manual and the only washer retainer is from the (body,modulator pressure valve) above the control valve.
Also how can i make the shift of second to third and third to fourth to change a little bit stiffer???
It's about modulator adjustment or from the shift valves???
Thank you very much.
Chris

[dbarton291]

That is a piston retainer from the center support.

[dbarton291]

For the AT/MT/HT valve body:
Signal valves send signals. The decide when the transmission shifts.
Relay valves sump and apply clutches. You can't really change anything there.
The trimmer valves along with the trimmer regulator affect the harshness/smoothness of the shift.
The modulator valve tells the valve body what the throttle position is to affect the shift valves' timing of the shifts.

[dbarton291]

To stiffen the shifts, there are generally two methods.

One is to install a fixed shift plug in the modulator bore. You will have no shift modulation and all shifts will occur at full trimmer regulator pressure at fixed shift points.

The other is to play with stiffer trimmer springs until you get the shift to your liking.

Hope this helps.

[dbarton291]

One bit of advice though.....with the broker piston retainer in the pan....
That piston retainer came off of either the second or third clutch piston. That really needs to be fixed, especially if you're going to try stiffening some shifts.

[chris19a]

Thank you very much for your respond my friend.
A couple of days ago i opened the oil pan to see how can i make the shifts 2-3 & 3-4 a little bit stiffer.Then i saw this piston retainer.
Today i opened the modulator pressure valve, and the washer(piston)retainer missing according to the service manual sketch.So i must fix this.
Now about stiffen the shifts....
You said to play with stiffer trimmer springs.
You mean the springs of all the clutch trimmer valves?
Thanks..

[chris19a]

Or the shift valves ????

[dbarton291]

You can change out any of the trimmer springs to stiffer springs if you want. There is one for each clutch except forward clutch. Forward is applied off the selector.

Stiffer shift signal valve springs will make the shifts occur at a higher engine RPM but won't necessarily make the clutches slip less during each shift.

[chris19a]

Sorry again,
To the modulator pressure valve has a ring,spring adjusting.
Can i adjust something from there or i must install a fixed shift plug in the modulator bore as you said?

[dbarton291]

Modulator pressure in an Allison is opposite how it is used in a hydramatic. Lower modulator pressure means high throttle position. Cranking down the modulator pressure will make the trimmer regulator go higher, making the shifts a bit stiffer. It will help some, but the real fix for what you are trying to achieve is stiffer trimmer springs.

[chris19a]

Stiffer trimmer springs from the clutch valves right?
Sorry my English is not so well.
How easy is to find these stiffer springs?

[chris19a]

This is the 3-4 clutch trimmer valve.
You can see that there is two springs.
I must change both of them??

[dbarton291]

You said you had a service manual. It it is an Allison service manual, there is a wear limits and spring data section. You can choose stiffer springs based on the dimensions in the spring data information.
The outer trimmer spring controls the initial clutch apply pressure. That's the one that needs to be changed to stiffen up the shifts and make them feel more firm.

[chris19a]

Thank you very much.
I found the spring data..but one last question.
i can't do the two steps together? (stiffer springs & fixed shift plug in the modulator bore)?
Do you believe with your experience that i will damage my unit with this setup?