I have to hit the button too when I start to get below 1800rpms. I hate hitting the button b/c the engine revs really really high for a short period while I wait for the tranny to lock-up (I think that's what you call it when it's not slipping the torque converter). I actually let off the gas to have it lock-up sooner. Does yours do the same thing?

 

...and...


Unless the trans is "hunting" (shifting frequently/ up down up down) while on an incline I would not use the O/D button.

I use the O/D button for "deceleration" on downhills, I also do not use Cruise Control while towing (uphill) in anticipation of hill(s) I gradually increase speed to give me some momentum and in most cases the trans never downshifts.

YMMV.

 

Even with my light load of 4000lbs the engine will eventually have to down shift out here when we climb up the mountains. I use the button b/c it seems to wait way too long before it does it itself (1500 rpms). I wish I didn't have to b/c it just doesn't sound natural.

 

I don't recall the exact behavior, but that sounds about right. The rpms jump to the high 2000s if not to 3000 and it may settle in a little lower than that after a short time.

 

Yes, same here. I'm not sure what RPM it does it at but it seems like a lot of momentum is lost by the time the trans downshifts. I've never experienced hunting in and out of overdrive.

Maybe someone with EGT and an aftermarket/ODB transmission gauges will chime in. Mine seems happier in the mid to high 2000 range on a hill while maintaining speed/rpms vs slowly dropping speed/rpm in overdrive.

 

I have all the gauges and I'm still trying to figure this all out. When I do down shift, I lift off the pedal enough for the tranny to lock-up. Which by that point I'm doing 50mph. Then in the lower gear I'm able to accelerate back up to 60mph when going up the hill.

I've been looking into the chip tuners (i.e. php hydra) b/c everyone says how much better the truck shifts with it. I'm hoping w/ the chip it would shift at about 1700rpms on it's own and give a firmer shift so I don't have to slow down so much before the tranny locks.

 

Excellent advice and very good towing strategy Mark!
I have found that my custom Performance tune from 5Star greatly improves the trans performance and allows it to hold onto OD longer while climbing grades allowing my V-10 to stay in a sweet spot where it makes enough power to carry decent speed up most Interstate grades without having to downshift. I would assume that a similar trans tune would be a nice compliment to the 7.3 unless it would cause a lugging situation at a certain point, I know deezles don't like being lugged.
And I never use Cruise Control while towing, I like having total control with my right foot at all times with the trailer following me, and you can get better MPGs without CC. My typical OD button use if for engine braking on the downhills too.

 

I think we all get not to use the CC and get your momentum up before the hill.

The issue w/ the 7.3 is that it has a very narrow powerband say 1900-2200 rpms and then it waits way too long to down shift i.e. 1500rpms. Then when it does down shift there's a huge ratio gap between OD and 3rd gear (I guess it is) so then the torque converter is being slipped at a really high rpm which can't be good. So I let up on the peddle till it locks up. It's like the tranny needs another gear between 3rd and OD and some better smarts on when to downshift and how to lock up the torque converter sooner.

 

Check, I'm fortunate as the V-10 has a much wider RPM range where it makes decent power. I think a good tune writer could make that 4R100 work more like you want it to, quicker downshift and lockup and at a specific speed under high load situations to keep the 7.3 in it's sweet spot during the change. The trans performance improvements with my tunes were remarkable!

 

Thanks Tom, I use CC (while towing) in isolated flat lands, never in traffic or in inclement weather. If I were piloting your rig I would not use CC either.

As an example, this past weekend south of Macon below the "fall line".

 

It would be interesting to see trans temp, eot, egt and boost, in OD up a hill vs hitting the tow/haul button before the hill and running it at a higher rpm.

 

I just installed the gauges and have only towed once with them. I'll keep an eye on it and report back once we start camping again this year. I'm hoping this month sometime. If my memory serves me correctly I think the EGT actually actually goes down even though the engine is spinning up.

I'd be ok w/ the downshifting if it didn't sound like the pistons were going to fly through the hood and the tranny wasn't slipping so much.

 

I pull 8k TT and the 7.3 likes 1800-2000 all day long.
I find slower and the trans temp get high

 

Thanks for the feedback. Mine is the same, 2000rpm is golden. After re-gearing w/ the 35's, I run 65mph at 2000rpm. It's a little slow if you are not towing but our Ex is our tow vehicle.

I just got off the phone with PHP and asked them about their programs. They said the shifting is much firmer and sooner than stock for the tow profiles. I think I'm going to go w/ the hydra to get better shifting if for nothing else.

 

I just ordered my PHP Hydra from KT Performance. I'll update this thread w/ my impressions once I tow with it.