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Bus Discussion => Bus Topics ( click here for quick start! ) => Topic started by: Cliff on November 26, 2007, 07:16:21 PM

Title: Allision 740 transmission
Post by: Cliff on November 26, 2007, 07:16:21 PM
This is behind a 8V71 Detroit engine.  The problem is overheating.  Can the oil level on the transmission has a bearing on the overheating., ie maybe the transmission not locking up?  Need some expert comeback as to whether our assumptions are correct.
Cliff
Title: Re: Allision 740 transmission
Post by: TomC on November 26, 2007, 10:43:56 PM
There are many things that can cause heating.  Lock up clutch slipping, any of the other clutches slipping, bad bearings causing drag, clogged up transmission cooler.  If you have a tachometer, you can test the transmission gear by gear to see if it is slipping just by watching the tach and speedo relationship.  Both should move exactly the same when locked up (at the top part of 2nd gear, usually around 30mph).  If the tach moves up and down when locked up, the trans is slipping.  Good Luck, TomC
Title: Re: Allision 740 transmission
Post by: Sojourner on November 27, 2007, 12:13:10 AM
Quote from: Cliff on November 26, 2007, 07:16:21 PM
The problem is overheating.

Yes if it like what TomC said but are you sure it the trans is the cause of overheat problem?
How did you determine which is one of the two or both engine & trans?

If your trans oil has burnt smell & brown colored and few drop of oil onto clean white tissue to look for metal particle & clutch compound...then you may need to pull pan to inspect. Otherwise if trans is ok but yellow oil (old fluid)...need changing for new.

Suggest to look up for knowledgeable bus or Allison transmission technician.
Here a link and fill in for nearest location:
http://www.allisontransmission.com/locator/mappoint/index.jsp?country=US

FWIW

Welcome new member on board!

Sojourn for Christ, Jerry
Title: Re: Allision 740 transmission
Post by: makemineatwostroke on November 27, 2007, 03:54:10 AM
Cliff, oil level is very important too much or not enough will make a 740 overheat. you can download a trouble shooting guide from Allision it will cost you a few bucks but is very helpful