Transmission cooler

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Dave DeSalvo
Posts: 29
Joined: Mon Jul 30, 2007 10:36 pm

Transmission cooler

Post by Dave DeSalvo »

Am about to replace my damper plate as a preventative measure. Following the excellent directions provided by other owners, I know that I will be pulling the transmission and will have an opportunity to replace the fluid from the bottom of the tranny for the first time. My M35B operators manual talks about a transmission cooler as a "possible" external attachment and recommends having a spare on board. I haven't been able to identify this unit. My question is did the motor / transmission combination come with the cooler and if so what experience do other owners have with this unit?

Thanks for your help.

Dave
AynB
Posts: 88
Joined: Tue Jul 08, 2008 8:13 pm

Re: Transmission cooler

Post by AynB »

Dave, I need to voice a couple of things here.
The stock engine / gear did not come with the cooler.
The cooler is nothing more than a cast piece of metal with a number of fins on it for heat dissipation that bolts directly to the side of the gear box. Nothing more, no plumbing or fittings. So it's basically trying to dump 'some' heat into the engine compartment - which is already pretty warm.
You wrote " will have an opportunity to replace the fluid from the bottom of the tranny for the first time " . How many hours do you have on the box ?
We have posted a number of threads on the forum about the ZF Hurth gearbox and the bottom line is that you really should consider replacing the fluid every 100 hours. You don't have to remove the gear to properly drain it. Even if you put the "cooler" on. The 500 hour number is pretty much a joke. We've sent samples of fluid after a 100 hour change to labs and got the reports back that the fluid was already toast.
As for the damper - good and wise move, just upgrade the damper to a high arc one - will make everything last longer.
Al
S.V. Halona
#17
Dave DeSalvo
Posts: 29
Joined: Mon Jul 30, 2007 10:36 pm

Re: Transmission cooler

Post by Dave DeSalvo »

Thanks for the feedback.

I have been changing the trans fluid at each oil change which has been every 100 hours or each season, whichever comes first. My motor has about 420 hours on it and the trans has been acting OK. I have been drawing the fluid out through the dipstick hole. I seem to be able to get most of it out but taking the fluid out through the actual drain will allow me to see any metal filings which may be there.

The trans cooler pictured in my owners manual has fittings for coolant to flow thru it. The text in the operators manual talks about coolant flowing through the cooler unit. My hull is #383, perhaps the "cooler" was a fitting on the M-40B or M-50B which the manual also covers.
leigh weiss
Posts: 208
Joined: Mon Mar 05, 2012 7:32 pm

Re: Transmission cooler

Post by leigh weiss »

Dave,
I think you are correct about the cooling fluid running through the trans heat exchanger.
I have not added this to my engine but thought about it. The cooling fluid I would use would be the same run going to the DHW water tank. This seems to be the easiest solution with less plumbing. Let us know what you do and where you found the external heat exchanger. As a final note: you might want to mount the heat exchanger with the aid of heat sink grease (used on high power transistors) between the two surfaces for better heat conduction.

Leigh
Leigh and Donna Weiss
Brisa #155
Georgetown, MD. USA
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