Hello there,

So, as the title/subject mentioned, this is our second 6.2L gasser. First one was 2012 F250 XL CCSB FX4 with the 4.30 rear end. Got it to pull a Cougar 28RLS (basically 30 ft tip to tip) travel trailer, along with the usual occasional stuff - not as a daily driver. We got it with ~102k on it, sold it with a little over 121k, and it ran *great*. First time with a 6 speed and integrated trailer brake, and with the WD hitch set up right, there were times when I had to look back and check that the trailer was still there! Going over mountain passes out west there were some times when we had to slow down to say 55 by the top, but even in 3rd gear it took it like a champ.

We decided to change to a slide-in truck camper, and sold the '12 F250 XL short bed for a '18 F350 XL long bed 'extra' cab with the plow and camper packages, bringing the GVWR up to 11.5k. Fully kitted out, our camper uses every bit of that weight rating, but the truck handles it like a champ. I'm fairly sure this truck has the 4.30 rear end as well - the sticker on the door shows a '4M' code in that slot.

Except when going up almost *any* kind of hill.

If it has to kick down into 3rd, with that kind of load on it, for any length of time - like a minute or less - some really loud and unpleasant noises start coming from the engine bay. Back the speed off down to 55, maybe 50, sometimes even 45, and it *usually* stops. Shifting to 'M'anual and popping it to 4th stops whatever it is immediately. It did it the very first time we went over the pass east of Butte MT, both coming and going, in '21. Last year it happened at almost every mountain pass, and this year we're fighting it just going over some of the big 'rolling hills in southern MT / northern WY. It does it on downhills too, though less repeatably. Basically anytime the transmission is in 3rd and the RPM are high (< 4k), there it is.

I've asked around locally, and without actually being there and hearing / *feeling* it first hand the best guesses I got was maybe it was the engine fan or something like that. The way it seems to be tied to the engine RPM and transmission gear i.e. 3rd vs 4th seems at odds with that theory, though. It doesn't sound like a fan starting up, it sounds like a whole 'nother *engine* starting up in there!

I was hoping someone here might be able to help me out with this. Seems kind of odd - and maybe this is naive on my part - that there'd be this much difference between *towing* 8+k, and *carrying* 4k with the same engine and rear end.

Thanks!

 

im guessing your not getting any codes? can you describe the sound coming from the truck under load? Whats the trans temp when your having this problem?

 

No codes when I checked with an OBD-II app (Torque, if it matters). I'll have to see if I can capture an audio recording of the noise, and see what the trans temp is next time it happens - probably tomorrow, when we're back on the road, from western Nebraska up thru SD to pick up I-94 by Belfield ND.

 

In case I don't get an audio recording... I'd say initially (first few seconds) it maybe sounds like a motor or fan starting up... but quickly becomes louder than the engine *and* transmission together to where it's almost all I can hear. It's definitely a little higher pitched than the other engine sounds - not a lot, but a notch or two higher.

 

Sounds time like your fan is engaging, could be a faculty fan or your transmission or motor getting warm enough to bring it on. I know when I pull ours hard in lower gears it will come on and be very noisy. I think the computer monitor monitors the speed (air moving over radiator) and temps both transmission and motor and brings it on before they climb to high.

Denny

 

based on the HP Tuners tables I have for my 2016. the fan speed is monitored by ECT vs ambient air temp, ambient air temp vs trans oil temp, A/C pressure vs ambient air temp, Max RPM, Min RPM, WOT disabled time and desired ECT. those are just the tables that i can adjust. there might be more in the background that are not adjustable.