Transmission temperature question

Bruce Herrington

Bruce Herrington

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Jan 1, 2000
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The stbd gear runs 200 degrees while the port side runs about 160.. Could this difference be due to the recent rebuild? Didn't begin monitoring temps until stbd rebuild 2 months ago.
 
Assuming these are IR gun temps I don't think so. Have you cleaned the oil cooler??
 
Could the hoses between gear and cooler be causing the higher temps? I've compared temp readings for engines/gears and they are within a few degrees of each other except the gear.
 
Flush and inspect cooler look through it for junk
 
FWIW, With the aid of a short sections of garden hose and some adapters and an inline on/off valve to the flush supply hose , I back-flushed the cooler on both engines into a 5 gallon bucket a few days ago as I do at least once a season for maintenance. As usual I found several pieces of leafy sea weed big enough to at least likely block a few tubes in the bundle. That weed is larger than anything that I could imagine slipping through the RW inlet scoop strainer or Groco sea-strainer basket, so I suspect it may get in when smaller and somehow gets retained and grows a bit.

The 1st time I saw this I knew that back-flushing would be added to the maint. routine.
 
Flushed U-cooler; nothing but clear water came out. Did notice that shaft will not turn by hand in either direction. Port side shaft will turn easily by hand.

Could the cutlass bearing have been damaged when shaft was pushed back to remove the gear? Running gear was painted
 
I wish that you had looked in the cooler really well. Flushing just is not as sure thing
 
The amount of water that came out seemed to indicate all is good. I'll do a visual tomorrow. Thanks.
 
I guess it is also possible that the oil line is obstructed in some manner
 
What kind of engine/gear?

Every time I ve had a gear running warmer than the other one, especially at slow speed, it turned out to be a raw flow problem. Apparently the gear will run a little warmer before the engine coolant. If exhaust flow if visible, check for a difference between port and stbd. If not, feel the raw water pump cover or check temp with ir gun. In one case, the warmer gear was caused by a pin hole in the fuel cooler on the suction side of the pump (so no leak but air coming in) and another time by debris in the fuel cooler restricting flow. Engine coolant was fine, and gear temp was fine at speed but 20 deg higher at hul speed.
 
Borg Warner 72c coupled to 2002 Crusaders (454). We've checked all the lines for obstructions, didn't find any. Temps for both engines, shafts, exhaust are within a few degrees of each other, except the actual gear. Even the fluid line at the gear is less than 130 degrees.
 
Is there by any chance a similar temp difference on the engines at the riser/elbows (RW side?)

Presumably ATF levels are still optimum. Do your transmissions have replaceable filters ( mine do not) ? If yes, it might be worth inspecting the stbd one, and if no filter you might consider ATF fluid drain & fill even though it has only been 2 months. That way you could get a good inspection of fluid condition after the rebuild and even strain and reuse if it looks very good.

Confirm the hydraulic hoses to & from the cooler are not bent too sharply & crimped at all. Were the hoses inspected internally at time of rebuild?

Anyone have any idea whether an air-in leak at a hose fitting on suction side ( if there is such a thing) could raise gear temps without any visible clues on the stick when checked? Or perhaps the stick was only checked when the ATF had a chance to settle out? But I'd think running with aerated fluid would likely push froth out the vent or maybe pop the stick.

What transmissions and engines? Is there any reasonable way to get a pressure reading underway? ( for example, on pfd p. 4 ,this VD 71C/72C manual says check fluid level at operating temp "max 190*F fluid temp" , and also gives spec pressure reading for F,N & R at various rpms : http://www.boatfix.com/merc/Servmanl/16/16B8R2.PDF )
 
Well you answered a bunch of those questions while I was pecking away at the keyboard. :D
 
Sandy, I try to rule out the obvious before posting a question here. Even read similar threads looking for answers.
You guys offer great feedback; someone will benefit from the "keyboard pecking". :-)
 
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