Cummins QSC “Gear Temperature Alarm”

[brewster16]

I got this alarm on the starboard engine. Gear temp, running at 21 Kts was 190F as compared to the port engine at 150F. Once I shut it down it cooled down and enabled me to get to my destination.

Anyone with insight or knowledge on how to handle this is welcome to comment as I will be heading home at the end of the holiday weekend.

 

[ttmott]

That is typically associated with the clutches inside of the gear slipping. If it were the gear oil cooler raw water flow then you'd see higher temps on the engine also. Slipping clutches is caused by hydraulic pressure being too low.

 

[Halfhitch]

But before getting involved into hydraulic pressures, makes sure it's not just inconsistencies in either your gauges or the sending units by switching the wiring between the gauges and if they still tell the same story, then switch the senders to opposite gears. If it remains the same through that exercise, then it's time to check relief pressures on the clutch control system.

If you verified there is that difference with an IR heat gun then no need to question the gauges though.

 

[brewster16]

That is typically associated with the clutches inside of the gear slipping. If it were the gear oil cooler raw water flow then you'd see higher temps on the engine also. Slipping clutches is caused by hydraulic pressure being too low.

 

[brewster16]

So does that mean that the transmission fluid level may be too low?? Is it a simple do it yourself fix like add trans fluid or is it tear down the transmission time??? Please educate me about this as I don’t know much about this.

 

[km1125]

So does that mean that the transmission fluid level may be too low?? Is it a simple do it yourself fix like add trans fluid or is it tear down the transmission time??? Please educate me about this as I don’t know much about this.

It could, but it probably would have to be pretty low. Have you even checked the levels to see where they're at?

If it is low, you need to figure out where it went. But you'd also want to know the last time it was at the 'full' mark to know how long it took to get that low.

 

[brewster16]

I’ve never checked the transmission fluid level. I will be checking first thing tomorrow.

 

[ocgrant]

I’ve never checked the transmission fluid level. I will be checking first thing tomorrow.

one check it yes, secondly how long has it been since it was replaced?

 

[brewster16]

Grant, to be honest I’ve never replaced it and gave it a cursory check here and there mostly trying to understand how the plunger/dipstick is situated. I have very little knowledge about the QSC/ZF transmission system. I’ve been reading through a bunch of posts from CSR but I’m trying to piece them all together. Some guys talked about filters or screens in their trans, some guys said my QSC’s don’t have any filter to worry about….ANY guidance you can offer is very welcome…

 

[brewster16]

Grant, to be honest I’ve never replaced it and gave it a cursory check here and there mostly trying to understand how the plunger is situated. I have very little knowledge about the QSC/ZF transmission system. I’ve been reading through a bunch of posts from CSR but I’m trying to piece them all together. ANY guidance you can offer is very welcome…

I’ve never gotten a “gear temp alarm” before and just to recap, the port gear temp was 194 which eventually cooled back down allowing me to run the boat but it was again creeping up as I approached my current destination. I want to emphasize that there is no grinding or rough gear noises putting it in to forward neutral or reverse. I also want to emphasize my engine temp remained at its usual 172F. Right now I’m open to suggestions as I anticipate returning to my home port tomorrow.

 

[ttmott]

My advise - Don't push it until you know what is going on.
Slipping clutches generate a lot of heat. Too much heat and the clutches will warp and then they will unable to be disengaged. You will be stuck in gear. Attempt to put in reverse will just kill the engine - start the engine and the boat will move even in neutral. It is terminal and expensive.
If you have the ZF 85IV gears then a common issue is the filter access cover comes loose and it leaks air. That cap (held in place by a single screw which expands an O-ring outward for seal to the case) isn't the best design, and is on the suction side of the hydraulic pump; if it leaks any air the hydraulic system will greatly drop in pressure which, in turn, will not provide the clutch clamping force and consequently slipping.

 

[km1125]

Post your exact model of the transmission (there should be a placard on it somewhere) and you'll get much more specific advice!

What ttmott says!!! Don't push it even if your temps aren't increasing, as the clutches may well be slipping and wearing and even if they don't overheat and warp, they will become useless. You won't hear any noises when this happens, as all the other noise would overwhelm the slight noise that the slipping clutches make. If your engine has a filter and you've never replace it, that could also cause an issue as that would be a restriction in the flow of trans fluid. And the more it slips, the more debris gets caught in the filter.

 

[Woody]

Look around and you should find a tag with all your gear info on it. ZF manuals are easy to find online. I don't know what you have but mine doesn't have an actual filter on it. Mine has more what I'd call a strainer that would only catch quite large particles.

Once I had a situation where my port side felt like it was partially engaging/disengaging while in gear at idle speeds. My oil looked like new but had a near two hundred hours on it. I changed oil and problem was gone. Had that not happened my next step would have been to check pressure which is easy to do, although you need to get a gauge.

 

[brewster16]

Several times you guys have mentioned "hydraulic pressure". Is that the same as the reading on Vessel View called "gear pressure"? If so, the reading for "gear pressure" was 343ish on BOTH transmissions throughout this situation. Forgive me, I'm just trying to learn about this system.

 

[ttmott]

Several times you guys have mentioned "hydraulic pressure". Is that the same as the reading on Vessel View called "gear pressure"? The reading for gear pressure was 343ish on BOTH transmissions throughout this situation. Forgive me, I'm just trying to learn about this system.

It is the same. The pressure you are showing looks to be OK if it is stable and you verified that.
At this point I'd swap the temperature transducer between the two drives and see if the problem follows the sensor. The temperature transducer should be located on the gear cooler and pretty easy to get to.

 

[brewster16]

My transmission is ZF280IV. Both transmission fluids levels are at the top full mark. Still no grinding, popping, sticking or any other abnormal noise from the port transmission during shifting or running. However, once again port gear temp inches up 40F higher then starboard side. Are these findings all pointing to clogged transmission gear cooler?

 

[swaterhouse]

There isn't a spin on filter for your gearbox but there is a screen and magnetic plug at the bottom of the gearbox. I can't recall the exact size wrench but it's like 30mm or something like that. Your drain the fluid, remove the plug and screen, clean them off and replace the crush washer.

Fluids should have been changed every other year.

 

[ttmott]

That temperature sensor should look something like this (from my boat the sensor on the right) -

 

[ttmott]

My transmission is ZF280IV. Both transmission fluids levels are at the top full mark. Still no grinding, popping, sticking or any other abnormal noise from the port transmission during shifting or running. However, once again port gear temp inches up 40F higher then starboard side. Are these findings all pointing to clogged transmission gear cooler?

Again - if your gear cooler was plugging up on the raw water side, your engine temperatures would also increase. All of the engine's cooling water goes through the gear cooler.

 

[ttmott]

If your shifting solenoids are not correctly directing the hydraulic fluid and causing the clutches to slip then, like low hydraulic pressure, the clutches will slip.
At this point if further TS is out of your wheelhouse then getting a service rep would be best.