Hard shift high to low range

[Mrkentee]

Eaton 13 speed trans:
When shifting from high range to low range it sometimes, not always, slams into low range. But:
1. It only happens when the weather gets warmer, like now.
2. Only from high to low. Shifts fine going up.
3. Only if speed is between about 9 mph up to 15 mph. I don't use low range over 15 mph.
If I slow down to 5 or 6 mph, it doesn't do it.

I'm replacing the filter/regulator. It's cheap enough, $50.
Other than that it could be synchros.

Any ideas?

[Hammerhead]

Sounds like the synchro is glazed, or the oil is old or possibly contaminated; i.e. Liquid cooler leaking.
Pull a sample and have it checked for coolant ASAP! Coolant intrusion destroys synchros, and fixing it before it goes BOOM is much cheaper...don't ask me how I know, I just do.

[Mrkentee]

(05-06-2017 )Hammerhead Wrote:  Sounds like the synchro is glazed, or the oil is old or possibly contaminated; i.e. Liquid cooler leaking.
Pull a sample and have it checked for coolant ASAP! Coolant intrusion destroys synchros, and fixing it before it goes BOOM is much cheaper...don't ask me how I know, I just do.

Oil was changed less than a year ago. When I get service at Speedco, they put a little on that plate to show you when they check it. Always looks good. I will check it.

[hhow55]

Maybe this help's http://www.roadranger.com/ecm/groups/pub...0902hr.pdf

[Hammerhead]

(05-07-2017 )Mrkentee Wrote:  Oil was changed less than a year ago. When I get service at Speedco, they put a little on that plate to show you when they check it. Always looks good. I will check it.

A visual look at a couple of drops on a plastic card will not tell you if you have small coolant intrusion.
The fiber material in synchros absorbs small amounts of coolant masking the intrusion, but the chemicals in the coolant destroy the fiber material.
The synchro material is somewhat sacrificial. It's purpose is to either speed up or slow down the gears in the back end of the transmission making smooth shifts. When they don't function as intended, the gears don't match speed quick enough which is why it hammers in hard. The air shifter is bringing the gears together whether the speed is matched, or in this case not which is why it's shifting hard. Once your stopped, or at very low speeds, the gears are no longer spinning, or doing so slowly enough, which is why it doesn't do it then.

[Mrkentee]

(05-07-2017 )Hammerhead Wrote:  

(05-07-2017 )Mrkentee Wrote:  Oil was changed less than a year ago. When I get service at Speedco, they put a little on that plate to show you when they check it. Always looks good. I will check it.

A visual look at a couple of drops on a plastic card will not tell you if you have small coolant intrusion.
The fiber material in synchros absorbs small amounts of coolant masking the intrusion, but the chemicals in the coolant destroy the fiber material.
The synchro material is somewhat sacrificial. It's purpose is to either speed up or slow down the gears in the back end of the transmission making smooth shifts. When they don't function as intended, the gears don't match speed quick enough which is why it hammers in hard. The air shifter is bringing the gears together whether the speed is matched, or in this case not which is why it's shifting hard. Once your stopped, or at very low speeds, the gears are no longer spinning, or doing so slowly enough, which is why it doesn't do it then.

The only thing I don't get is why it didn't do it sll winter, but now as the air temp increases, it starts doing it again.

[in2trux]

Hi lo spliter hanging up or lagging. Maybe time to change the valve.
Moisture could have corroded valve internals. Higher temps=tighter tolerances and it's not moving fast enough or sticking for a second or two. Just enough to throw synchronization.

[Mrkentee]

(05-08-2017 )in2trux Wrote:  Hi lo spliter hanging up or lagging. Maybe time to change the valve.
Moisture could have corroded valve internals. Higher temps=tighter tolerances and it's not moving fast enough or sticking for a second or two. Just enough to throw synchronization.

Transmission people didn't seem to think so. But, could be.
I changed the filter/regulator. It seems good but haven't put it to the test in hot weather. Also took a sample and sent it off.
One other thing: if you can picture the back of trans. The big line that came from the valve on the bottom left (below the fluid level), that goes to the filter/regulator, had a little bit of fluid drip out of it when it was hanging down disconnected from regulator. That seemed odd. I haven't asked any trans people about that yet.
I have a photo in my iPhone, but can't figure out how to post it.

[kmk]

Range select cylinder might be dragging or leaking air past the o-rings causing a delay in moving. Rear o-ring is easy, front one more involved, check the repair manual on Eaton's site.