HT740 slipping

lostagain · July 21, 2020, 05:41:45 PM

Today not too far from home on the way back from a one week road trip, my HT740 started slipping in torque converter mode. It heats up too. It still shifts fine. It works fine in lock up. The oil is up where it should be. No leaks.

I am going to drain the oil and drop the pan. From there on, I don't know what I am looking at. Isn't there a filter there? What else should I be looking for?

I see I am going to learn about the HT740, lol.

I am hoping it is fixable with it on the bus. Taking it out doesn't look like fun...

JC

Taibob · July 21, 2020, 08:00:33 PM

JC
Give us your update on the terrible Bus crash on the
Athabaska icefield. {ex Brewster coach} 3 lost lives, many
extreme injuries.
Wreckage removal in progress, That was a large unit to roll
over down the hill.
Regards Bob

rusty · July 22, 2020, 05:59:04 AM

OFF TOPIC SHORT RANT.I am thick skinned and don't give a damn about being PC. Can we get rid of the big ugly thump in a reply like the on above. Not a good look
RANT OVER
Wayne

lostagain · July 22, 2020, 07:00:49 AM

Bob, how have you been? Re the icefield crash, I don't know anything other than what is in the news.

JC

lostagain · July 22, 2020, 07:01:36 AM

Guys, I am really looking for advice on my transmission. Thanks.

JC

dtcerrato · July 22, 2020, 07:10:13 AM

I heard the Ice Field roll over was caused by a land slide. Not even a full track would deal with that. Now lets get back to JC's transmission!

luvrbus · July 22, 2020, 08:47:35 AM

May have a broken spring in the valve body check all your pressures at the front and rear and pull the governer check to be sure all the plastic is still intact lol maybe start a new topic

lostagain · July 22, 2020, 09:37:22 AM

Thanks Clifford. I have an Allison service manual for it. 328 pages! I have some studying to do...

So far I am assuming that my shift sequence is: 1C-2C-2L-3L-4L. I'll have to confirm that from the serial number.

Thinking back at the symptoms: it works normally from a stop in 1 and 2, then slips beyond that. So I am thinking that it is the lock up that doesn't work.

Lots to learn... I have rebuilt many engines of all types, but never been into any transmission...

JC

lostagain · July 22, 2020, 09:42:57 AM

https://www.scribd.com/document/326083921/HT-700-Hydr-Service-Manual-SM1270-199904?fbclid=IwAR18deuZNCVhmer4AixMKPpCJHKMraX5GkUsR5SMcOrRmCyP5urXnUaaDFQ

This is the service manual I have. Might be useful for someone else.

JC

luvrbus · July 22, 2020, 10:30:07 AM

Quote from: lostagain on July 22, 2020, 09:37:22 AM
Thanks Clifford. I have an Allison service manual for it. 328 pages! I have some studying to do...

So far I am assuming that my shift sequence is: 1C-2C-2L-3L-4L. I'll have to confirm that from the serial number.

Thinking back at the symptoms: it works normally from a stop in 1 and 2, then slips beyond that. So I am thinking that it is the lock up that doesn't work.

Lots to learn... I have rebuilt many engines of all types, but never been into any transmission...

JC

no

Quote from: lostagain on July 22, 2020, 07:01:36 AM
Guys, I am really looking for advice on my transmission. Thanks.

JC

If you do it I have the snap ring tool I can ship you it is a bitch without it,when you get into the lock up stator there thin brass clutch parts that break it is easier to buy a rebuilt stator than worry with

lostagain · July 22, 2020, 05:27:38 PM

I drained the oil: looks good. Dropped the pan. Took the governor out: looks good. The plastic gear looks good. Everything so far looks clean. Now I am studying the manual... I'll take the valve bodies out tomorrow.

JC

lostagain · July 22, 2020, 05:51:44 PM

The model no is: 740D 7D30. Serial: 17352.

robertglines1 · July 22, 2020, 07:50:33 PM

ck modulator on side for leak. Had to change mine once on 740=you could actually hear bubbling in pan. Just put shop air to it in a cup of oil. no bubbles=ok.

Van · July 23, 2020, 10:10:06 AM

Quote from: lostagain on July 22, 2020, 05:27:38 PM
I drained the oil: looks good. Dropped the pan. Took the governor out: looks good. The plastic gear looks good. Everything so far looks clean. Now I am studying the manual... I'll take the valve bodies out tomorrow.

JC

Hows the filter?

lostagain · July 23, 2020, 02:24:16 PM

The filter has some metal shavings on it. Not a whole lot, but noticeably some. Is that bad?

I started removing the valve body cover plates (heavy suckers when you're working upside down!). Looking at the manual, I am thinking that I am in over my head. And what if I fix something, there might be something else wrong deeper in there. And I don't know how old it is. It came with the bus. I think I remember the previous owner saying he got it used.

I can get a rebuilt HT740 (Coachguard), never installed, for a good price, not far from home.

I would have to pull the engine to swap it out. But that doesn't scare me. Been there, done that...

I am talking myself into doing that...

JC