Hi can any one help me regarding a problem I'm having with a Caterpillar 740 truck. When a gear is selected either forward or reverse it engages really aggressive bang. The truck has done 14000 hours but has always been serviced as per manufactures recommendations and we run it on Shell spirax 10W. Once the gear is selected it changes and runs perfect and the tranny never gets above half way on the temp gauge. I was thinking could it be some sort of soft shift solenoid causing the bang. Thanks in advance for any input on this it is appreciated. Steve
A couple of questions; How long have you had the machine? Has the noise always happened, started gradually or came on suddenly? Are you comparing it to other 740's? Why the 10W transmission oil? It's not a common grade and for your ambient temperature, it's (arguably) too low. I would be using 30W, although I don't think it's going to affect the diagnosis at this point. With 14000 hrs, I'm guessing either AXM or B1P serial number?
This bang you refer to. Appeared all of a sudden or has always been there but recently got much worse..? Serial Number prefix..? B1P maybe..? Without knowing a S/N it's difficult to know what level of electronics you are dealing with in the transmission and what Diagnostic Codes you may have and their significance. I'd be thinking more along the lines of a drive shaft U-joint starting to get some wear in it, or maybe even something in the drop box. Has anyone watched the driveline to the centre axle when you shift from neutral into 1st or reverse..? Does it jump at the same time as you get the bang..? Do you do oil analysis and if so what results are you seeing..? If it was mine I'd be running SAE30 TO-4 in the transmission rather than 10W and any brand but Shell because I don't like their TO-4 oils. That's personal preference though, and probably nothing to do with your present problem, although I do really believe an SAE 30 oil would be better in UK conditions. Edit: It appears as though my learned Australian friend and I were both typing at the same time ......
I'm not saying you don't have a problem but from my experience with these 740's most of them bang pretty hard going into gear from neutral. I was concerned at the first one I saw do that but have never seen a failure because of it.
Thanks to both of you. Serial number is B1P02858. Il get the oil changed over on the next service, how ever I would say our ambient tempratures are low, we live in Cumbria northern England where average temp is 10 Celsius. Regarding the clunk it has always done it but it has got slightly worse recently but not excessively.The machine does not jump when engaging and all the drive shafts seem ok as do the diffs. I know on our Volvo trucks they have a soft shift solenoid that can cause harsh engagement but I'm not as clued up on the Cats.
Mobiltech when I was inspecting the machine at the auction prior to us purchasing the machine it was one of a batch of 6 from Zeppelin cat in Germany, every one of them banged when engaging gear so I did figure it must be a trait of these machines. I just thought something must cause it and I know a new tranny is in the region of £20000 hence my concerns.
I think il collect some oil samples, the machine has only done 200 hrs on new trans and drop box oil will this still show what's needed for sos
When you have the SOS sample analyzed pay the extra (if it is extra with Finning, it was with our dealer) and ask them for the Particle Count (ISO Code). Check the drive shaft movement when you engage gear with the machine stationary as suggested in my post #3 above. I agree with you about what the Maintenance Manual apparently recommends regarding ambient temperatures and oil viscosities for the transmission, however to me unless you're above the Arctic Circle you should be using SAE30 TO-4 in that compartment. When the weather's really cold in the winter let the machine run for a few minutes while the operator is doing his pre-shift inspection and you'll be fine with 30. Just don't thrash a really cold machine before warming things up a bit, it should be a given but I'll throw it out there just in case. According to the manual SAE30 covers an ambient temperature range from 0 to 50 DegC so you should be fine. As an aside I would say SAE30 in the transfer box and SAE50 in the axles
Yes, 200 hrs will be enough to tell if anything is going on. You asked the same question back in January HeavyEquipmentForums and said you were waiting for SOS results. How were they? What oil was in there at the time? At what point was the oil drained and the 10W put in? Viscosity of the oil is important for more than just its lubrication qualities in electronic controlled systems like this. The ECM will monitor the temperature of the oil, calculate what it thinks is the viscosity at that moment in time and adjust the clutch modulation times to suit. If the oil is an inappropriate viscosity to start with, it will throw the ECM's calculations off.