Allison HT70 6-speed

[tninov8r]

Looks like about 2 decades since this has been a topic of discussion.....

I have a leak on the bottom of one of my HT70 transmissions that is coming from a hole in the bottom of what I believe is in the area of the scavenger oil pump.

It drips about 1x every 30 seconds on high-idle and on a 6 hour I lose about 1.5 quarts, sometimes more.

It seems to leak more when NOT running than running.

After thorough review of my HT70 Allison Maintenance and Parts Manuals and cannot find any documentation of this hole, or it's purpose...other than to let fluid escape when it pool in the cast well just under the pump.

When this first started to happen, about 9 months ago, trans oil was NOT leaking from the bell housing hole but now is.

• Has anyone had a leak in this area or know the cause?
  Does anyone know who could work on/repair a HT70 transmission? We are in Tennessee but can ship/go anywhere.
  The local Detroit/Allison people in Nashville cannot even cross reference parts on a transmission that has been out of production for almost 50 years.

I commercially run 4 different MC8 Custom Coach Conversions with this HT70 and this is the only one with any issues and need have it addressed.

Please see pics attached.

[luvrbus]

Is that a wet converter or dry ? I have only been around a few and never saw that hole before,do the others you run have the same threaded hole ?

[tninov8r]

Good morning. It is a wet converter and yes, my other HT70's have that same threaded hole.

[luvrbus]

I don't have the H-70 manual, I do remember the wet converter was a a adapted Allision Industrial Power Torque Converter used in tractors and other applications like on drilling rigs. I have a friend in NM that bought the H-70 thirty + years ago to use behind a series 60 in a Eagle bus back then the B500 were selling for 25 grand, the hp & torque rating were to low for the series 60. I will get in touch with him he was well versed on the H-70. He still had that rebuilt old transmission in plastic wrap last time I was there