18 spd vs 15spd/9LL

Or...just hold that gear you are already in, until the terrain makes it practical to upshift.
Saving 3 seconds at the end of the day isn't going to make any difference.

 

I figure it uses the same gear as 1st except its in high range. No doubt that puts extra burden on it like .

I've got a synchronizer whining and crying ever since I had the heat exchanger fail and got water into the transmission. I want to get that switched to air/oil cooler quick as possible.

I'm pretty sure I can change it but getting parts on the weekend might be tough. I think MHC Kenworth has them local. I don't know what all I'll need. I've never been into a Eaton Fuller Manual tranny. I think they should be fairly simple like a dirtbike transmission just heavier.

 

Its just another 3 seconds in paradise right?
I wouldn't trade my truck for a suit and 4 walls any day.

 

Eaton Fullers are dead simple. Download the service and parts manuals off their website and its really nothing to it. A stand and crane would be beneficial. I did the 15 speed out of mine on the floor with a few blocks of wood and an automotive engine hoist.

 

I used the low gear position in high range many times when driving 9 speeds. I used to go from 3rd direct to low position in high range with 13 speeds so I could split that gear when pulling up steep hills in old 318s and the like with no power. 3 direct to high range low position is the same step as going to 4th, but then you can split that gear to high, then split to low 5th as smooth as silk.

I know there is a lot of debate about not doing it, but so far I never had a problem using that position on 9 or 13 speeds.

 

@Hammer166 I seem to recall knows these transmissions quite well. Maybe he could clarify?

 

I'd agree the 13/18 are more likely to get torn up by ham-fisted operation. But they are rated for much higher torque, and should last longer under big power with a good operator. A lot of the trucks with 15's tend to have shorter rears, too; and pull through the bad harmonic spots quicker than a higher geared truck.

As to the OP: the LL trannies are in the same cases as the 13/18, they just have different gearsets, so you can't really say they're any stronger. And by any qualitative measure, the high-torque 18's are stronger than a 15 could ever hope to be, as far as ratings go. But what works in any application is a lot more complicated than just the ratings.

Yep, more input torque into the high range of the auxiliary. A different but similar issue as to why 13's are prevented from splitting in low range. If you spend some in the manual looking a power flows you can see the unique paths of the oddball gear combinations.

9's don't have the splitter section in the auxiliary, so that helps. Eaton actually made what was called a performance 9 speed that had you use that gear all the time. That tranny had a very short jump from 8th to 9th, almost like a split. So you skipped the big hole in low range and caught the dead gear for 5th.

That said, I too have occasionally used the dead gear going around corners, I'm just much easier on the throttle when it does happen, and have never had issues. My last truck was at 800K when we put a clutch in it, and the mechanic who put the front suitcase put the spacer in the wrong place, so it wouldn't stay in direct. As such, we had the top off trying to figure out what was going on. I wish I'd taken a pic of how good the gears looked, especially considering carhauler duty cycles. Shafts all nice and tight, too. It'd had the back half synchro kit done at around 600K, IIRC, and everything back there was in amazing shape then, as well.

 

I’ve been pulling trains and oversize for 9 yrs with a RTO14715. My Cat just loves the ratio set in that transmission.

 

Is there a kit to rebuild the back box or do you replace only what needs replacing?

It probably is a thin gear with a shaft running inside of it. Just have to be careful with it I guess as all gears. Any can break or bend with the right shock load.