Hey All,

My 1st post here, try to be nice LOL

I've got Mack 613 we swapped out a 10spd Fuller for a 9sp Rockwell this winter. Rockwell rm145a was used but known 2 B good, sat a while.

Following the swap everything was AOK, truck sat a month in Jan,
now will not consistatly shift to the hi side.

Pulled and rebuilt the air slave valve and feel sure it's working.

What is the next step?

I've got air going from the ASV to the back of the tranny in the L line,
but also have air coming FROM the back of tranny to the ASV thru the H line - is that right?

Or is there some leak inside that back valve thats causing this?

Dumb farmer here, not a very good truck driver but average mechanic,
all and any help appreciated

Thanks
CC

 

I don't know anything about the mechanics portion of the swap out...but I am wondering...Why did you swap out a Fuller...which is a top-line tranny, for a Rockwell..which is a mediocer(sp) tranny??

 

I'm not familiar with the Rockwell (Meritor) transmissions, but I have had that scenario on Fuller and Mack transmissions with air range shift.

The fact that you are applying air to the range shift cylinder thru the "L" line, and at that time you have air coming back up from the range shift cyl. thru the "H" line indicates to me that air is getting past the seals or "O" rings on the piston in the range shift cylinder (leaking thru from the lo side to the high side and coming back thru the "H" line.

This condition is usually more likely to happen in cold weather, because the "O" rings tend to shrink and are less pliable.

If this is indeed what's going on, fix it ASAP, because it could raise hell with the range shift setup if it's sometimes partially engaging.

 

Stan - the Rockwell was cheap, and a good friend had it in his Pete, so I knew it was good. The Fuller sits here in the shop ready for reman, and will go back in one day I'm sure. There's nothing at all involved in the swap,
bellhousing switched 'cause it's a Mack, other than that just a bolt-in.

Splitshifter - I thought I may have had some ice or trash in that back valve -
"piston housing" so I guess that'll be next. Thanks for the advise, it seemed
like the air coming back to the ASV would counteract the air from the hi/lo
switch causing the piston in the ASV to stay put.

I'll post back when I get into it, thanks,

CC

 

Splitshifter Wrote

"The fact that you are applying air to the range shift cylinder thru the "L" line, and at that time you have air coming back up from the range shift cyl. thru the "H" line indicates to me that air is getting past the seals or "O" rings on the piston in the range shift cylinder (leaking thru from the lo side to the high side and coming back thru the "H" line. "

Nailed it, Big O-ring on the piston had a chunk out of it, threw the range into
neutral or just a little ways engaged. 1 hour job, $20 seal kit. I appreciate the help!

CC