So when towing with an E4od; if you are on a bit of an incline in O/D but the tranny is not haunting back and forth between 3rd and 4th....what are the benefits to cancelling O/D and holding it in 3rd? Other than more power from higher revs.
Cooler temps?
Less clutch wear?
What effect does lugging have on an E4od (not that I would ever lugg excessively)
For ex. would it be easier on the trans to tow at 2500rpm in 3rd gear or 2100rpm in 4th at the same speed, even though its not trying to shift back to 4th.
You can almost think of it like how higher RPMs can keep EGTs under control.
Increasing engine RPM will also increase the pump speed in the transmission, and that means higher flow through the cooler. However since this is a hydraulic system, more flow also increases friction and the effect likely isn't linear (double engine RPM does not mean double the cooling of the transmission). Avoid using a manual torque converter unlock feature if you are on long steep hills at highway speed. The slip in the converter will add significant amounts of heat to the transmission even if you are at high engine RPMs.
If you are slipping one of the clutches at any point once in gear and hauling, you have minutes to pull over (maybe closer to seconds depending on how bad it is). Slipping shouldn't at happen ANY time no matter how much you are lugging it. If it slips, somethings wrong.
2500 RPM is a good speed for engine and transmission if you are loaded heavy enough to justify it. Since diesels run unthrottled, you are letting the engine ingest large amounts of air under those conditions for direct - in chamber cooling. (engine braking is an extremely effective way to rapidly bring EGTs down because of this) However, if you aren't wanting for extra power on flat ground, its just wasting fuel and you don't need the extra margin (but in terms of reliability, it won't hurt).
A few ways I decide to hit the cancel switch, or not are:
1: If EGTs are higher in overdrive than in the lower gear (by a significant amount, say more than 250F)
2; If coal starts rolling out the tailpipe (this doesn't always result in high EGTs if at lower RPMs and low power settings)
3; If the engine accelerates easily after downshifting (this is something I learned to anticipate) but NOT adding more fuel. Conversely, on flat ground popping it back into a higher gear for the same fuel settings can show the speedometer rise slowly. This last one is where it gets really finicky and aside from learning your own vehicle's ideal operating charactaristics, this doesn't have much to do with reliability anymore.
I guess what I'm trying to say, is drive the truck how it wants to be driven. Listen to the vehicle, get a feel for the powerband and the limits of the engine and take it from there.
Having a good transmission temperature gauge (which has been on my todo list for a few years now...
) is always a good idea. Having a good Pyrometer is also a good idea (mine busted almost a year ago, yeah I'm one to talk
)
are there kits for this type of tranny gauge?
