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Allison HT 740 No reverse
Posted: Sun Jan 01, 2017 4:19 pm
by Clydes Barn
Hey Folks, new to the forum, but appreciate any help. Got my 82 Silver Eagle in July and have been out on the road with it for a couple months. Had the tranny serviced before leaving, everything has been fine.
Suddenly today found out I had no reverse. Had it this morning leaving Ft. Lauderdale but got to Deland area and it is now in-op in reverse. Any ideas? I am surely going to have to have help as I checked the fluid and it's on point, linkage is fine and working.
Re: Allison HT 740 No reverse
Posted: Sun Jan 01, 2017 5:02 pm
by luvrbus
If you have 1st gear the clutch pack is good so it will be a stuck valve or a broken spring in the valve body
Re: Allison HT 740 No reverse
Posted: Mon Jan 02, 2017 5:08 am
by Clydes Barn
Thanks, I was hoping it was something like that. I will check it out this morning as I usually operate in drive, and never dropped it all the way down into the first gear position.
Re: Allison HT 740 No reverse
Posted: Mon Jan 02, 2017 8:35 am
by Clydes Barn
Haven't been able to get a hold of anyone yet today that can help, but here is a new update as of this morning. I started the bus and let it build air. I had not only first but also reverse was back. So it would seem that the problem has a temp related aspect to it.
Thanks again for the forum and the ability to seek answers.
Re: Allison HT 740 No reverse
Posted: Mon Jan 02, 2017 9:44 am
by grandpaD
Glad to hear your trans is cooperating with you again.
Hope it continues to do so.
Re: Allison HT 740 No reverse
Posted: Tue Jan 03, 2017 8:39 am
by luvrbus
It's funny how gremlins go away if you don't panic,but if keeps happening you may need to clean and polish the valves in the valve body
Re: Allison HT 740 No reverse
Posted: Tue Jan 03, 2017 8:57 am
by Clydes Barn
Hahahaha right? I have a guy coming today to change out the shift solenoid. He was an Allison tech at one time and feels that's the problem. We'll see but thanks for riding shotgun here with me.
Re: Allison HT 740 No reverse
Posted: Tue Jan 03, 2017 9:21 am
by luvrbus
LOL he going to have a tough time finding a shift solenoid on a 740
Re: Allison HT 740 No reverse
Posted: Tue Jan 03, 2017 9:40 am
by Clydes Barn
Ruh Roh! Well he'll be here in a few and then we can see what he knows.
Re: Allison HT 740 No reverse
Posted: Tue Jan 03, 2017 10:38 am
by Clydes Barn
Ok, so here's the update guys. I got a hold of my trusted Allison tech on the West Coast. Electronic transmissions have a shift solenoid and the local guy probably just assumed. It is a mechanical transmission and the problem is the valve body.
As it went into reverse the morning after the failure, it can be surmised that a broken spring is out which leaves a sticking valve. Run her but watch her, is the order of the day and if the problem stays away I will take it in when I get back for service and while they do that have them take the valve body out and spiffy it up. If it acts up again, at least I know what it is.
Thanks to you guys who responded during the crisis.