18 Speed transmission

BLOCKMAN

New Member
I have a 2018 Peterbilt 367 tri- axle with an 18 speed with 32000 miles 510 horse. When I am in say 5th Direct and switch to over drive the engine does not come down any RPM it jumps into gear jumping the whole truck. Took it to Peterbilt they replaced the regulator and O-ring, If it was O-ring issue it would shift slow. This has been going on for the last 2 months. Only way to go into Over drive is push the clutch in then select.
 

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My favorite thing about 18speeds was the ability to skip gears.

The only time I used absolutely every gear was loaded at 253,000 pounds.

This one was only about 149,000.

IMG_4220.JPG
 
For the trans to shift from direct to overdrive the engine rpm has to drop otherwise it will just grind and not go into gear.

Is this the first 18sp you have driven?
 
I've had Eaton Fuller 13 speeds do that, with ISX engines. I never did figure it out.
 
For the trans to shift from direct to overdrive the engine rpm has to drop otherwise it will just grind and not go into gear.

Is this the first 18sp you have driven?

I have driven 18 speeds all my life, Up till 2 months ago it shifted into over drive just fine. Now as soon as it feels no load or you let off the throttle it jumps into gear it does not grind. Others drivers have been have tried my truck out and said something is wrong. It seems like it has to my pressure but 2 regulators they both can't be bad.

I was mad aware the they do change the slider clutch gears in those transmissions years ago, They should have stayed with the old design IMHO
 

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