ECO Hubs Who needs 3:07 gears?

[GCecchetto]

Great info! I haven't seen the cruise control menu in cat et, I'll have to look for it. I do have access to Allison software, but how does target gear work? If I say target gear is two, does it always try to hit gear 2 when engaging the brake? Does it care about engine redline? I'm happy with the brake except I hate how aggressively it downshifts, rpms feel too high. I've heard some other trucks have thrown rods during pac brake use, although don't have much data on it.
Seems like I want target gear at 1, but be able to set an rpm limit lower than what it currently is so it will brake in all the gears, but not have the motor wound out quite so much?

I don't think there is TC lockup on 1st or 2nd, so no exhaust brake functionality. There is a setting in the ECM for the max RPM the trans should try to maintain on downshifts. By default it set at 2800. Yes, the trans will aggressively shift to the target gear.

 

[GCecchetto]

If you increase the target gear, you won't get much braking effect on medium and lower speed descent since the trans won't downshift and raise engine RPM to where the PAC brake is most effective. I assume you can manually shift it but what's the desire to not have this automated by the computer?

Because it's unintelligent and way too aggressive. If you're in high mountain passes on the freeway going 65mph, if you engage the exhaust brake it's going to aggressively downshift to 3rd and you'll be risking throwing a rod and be travelling at 30 mph when all you wanted was to coast down the backside of the pass at 65mph without using a bunch of service brake.

 

[GeneralDisorder]

Because it's unintelligent and way too aggressive. If you're in high mountain passes on the freeway going 65mph, if you engage the exhaust brake it's going to aggressively downshift to 3rd and you'll be risking throwing a rod and be travelling at 30 mph when all you wanted was to coast down the backside of the pass at 65mph without using a bunch of service brake.

I haven't had an issue and there's plenty of hills around me. If you lightly depress the accelerator the exhaust brake will turn off and you will coast without downshifting.

IDK I find it to be really pretty dang good overall and WAY LESS aggressive than it was before the ECO hubs. Compared to a stock reduction gear truck, the function of the exhaust brake and the downshift program seem to operate quite well. And it's easy to override with slight pressure on the accelerator. And as you found you can latch the cruise control so if you are wanting to maintain 65 down a pass it will do that for you.

It's not going to go anywhere near 3rd gear unless you slow down a lot - the TCM is programmed with maximum input RPM's that correspond to the engine redline or slightly below, etc. If the engine throws a rod it was going to do so anyway and just happened to coincide with a downshift because of the higher RPM.

 

[aw113sgte]

If you increase the target gear, you won't get much braking effect on medium and lower speed descent since the trans won't downshift and raise engine RPM to where the PAC brake is most effective. I assume you can manually shift it but what's the desire to not have this automated by the computer?

It doesn't go straight to 3rd. It goes to the next lowest gear that's acceptable for the engine RPM. So if you are in 7th then the trans will first go to 6th, and then 5th and 4th etc - but only as conditions are safe to do so - as engine RPM drops down to the acceptable limits of the next lower gear for maximum braking effect.

Don't want it screaming rpms when coming down the hills around here. I get it's more effective but I'd like to not have it at it's redline.ive been happy with its braking in 4th before it downshifts to 3rd.

 

[GeneralDisorder]

Sounds like you guys are worried about hurting the engine from over-revving. Empirical evidence suggests this isn't a failure mode we need to be worried about. Have never heard of this happening. Fuel consumption isn't an issue when in decel. And so we're down to nervousness over engine speed and noise I guess. Sounds like you want a setting that delays the downshift till you achieve a slower speed, not one that limits the gears available to the program.

 

[GCecchetto]

Sounds like you guys are worried about hurting the engine from over-revving. Empirical evidence suggests this isn't a failure mode we need to be worried about. Have never heard of this happening. Fuel consumption isn't an issue when in decel. And so we're down to nervousness over engine speed and noise I guess. Sounds like you want a setting that delays the downshift till you achieve a slower speed, not one that limits the gears available to the program.

Everyone has their preferences. I vastly prefer the way the brake works now with the changes. I also prefer not having it aggressively downshift to 3rd, which makes sense for the speeds the military drives the trucks, but doesn't for a truck that now can cruise with the rest of the traffic on the freeway. "I" prefer having the target gear set at 5th or 6th and then I can manually downshift to a lower gear when need be. For me, the aggressive downshift to 3rd slows me down way more than I need to, and yes, I'm well aware that you can apply the brakes engaging the exhaust brake and then release before it downshifts, but in my truck you have to literally be on and of the brakes in that scenario and the result is the exhaust brake not doing anything.

I didn't post what I did in an attempt to sway everyone to do what I did. Just so the other folks that want the EB to work a different way know what options are available. if you don't think the changes are good for you, don't do it.

 

[Ronmar]

Yea, without eco hubs these things cruise at max governed, so going to 2600RPM is not a real issue…

 

[GCecchetto]

Continual running of a motor at or near its red line isn’t good. Will these motors stand up to it? Sure, but I can assure you if you take two identical motors and run one a very high percentage of the time at or near its max governed rpm and the other at 1400-1800 for its life, the latter is going to out last the former.

The military has endless money to spend maintaining these trucks. Motor wears out or grenades they rebuild or replace it. Of course that’s if they ever keep a truck long enough to wear it out. I don’t have the budget for that, so I’d like mine to last as long as possible.

 

[GeneralDisorder]

Continual running of a motor at or near its red line isn’t good. Will these motors stand up to it? Sure, but I can assure you if you take two identical motors and run one a very high percentage of the time at or near its max governed rpm and the other at 1400-1800 for its life, the latter is going to out last the former.

The military has endless money to spend maintaining these trucks. Motor wears out or grenades they rebuild or replace it. Of course that’s if they ever keep a truck long enough to wear it out. I don’t have the budget for that, so I’d like mine to last as long as possible.

That's just it though - the engine isn't "running" at or near it's redline in decel. It's being spun by the transmission and is not under power - no combustion pressure is taking place. That's not the same kind of load as operating under WOT, 370 HP @ 30 lbs of boost pressure.

And over the road trucks with these same engines still operate under decel with exhaust brakes to the same redline RPM - just like our trucks. And do it for about 350 to 450 thousand miles till they wear them out.

As a mechanic that has rebuilt hundreds of engines and seen probably a thousand engine failures over my career - I've never seen one that threw a rod on decel under engine braking - I've seen people miss 4th and hit 2nd - that will typically trash up your valve train. And the one instance I was involved with a C7 that started to run away due to a turbo failure it caused several bent valves. Bottom end stayed togther and indeed drove hundreds of miles after the fact on 5 cylinders. The valve train was much more of an issue at excessive RPM than anything else.

In my personal opinion this is a non-issue. I'm much more worried about the engine oil pump, HEUI system filtration, oil bypassing the filter in a warped oil cooler, heads cracking, and head gasket failures, etc - all the things I've actually heard of happening on these engines. Even when the oil pumps start to give out - it typically doesn't result in severe bottom end failure. They stop running due to the HEUI system taking a dump from debris.

 

[GCecchetto]

In my personal opinion this is a non-issue. I'm much more worried about the engine oil pump, HEUI system filtration, oil bypassing the filter in a warped oil cooler, heads cracking, and head gasket failures, etc - all the things I've actually heard of happening on these engines. Even when the oil pumps start to give out - it typically doesn't result in severe bottom end failure. They stop running due to the HEUI system taking a dump from debris.

Understood, but the way the exhaust brake works after the mod is way more useful for my intended use of the truck. Given that the mode with the cruise set does not have the aggressive downshift, I will probably have the target gear set to 5th and see how that goes in the other two modes.

I don't think I have an oil pump issue but am definitely planning to add the filter between the HEUI pump and the head and would like to also add bypass oil filtration. I'll likely do my oil changes at 7500 miles for now, then likely extend that if I do install a bypass system.

Relative to the oil pump issue, shouldn't CAT be able to tell us what oil pump was used in the motor by the serial number? If you already have the revised style pump, no need to change it unless you are actually having a low oil pressure issue.

Now, back to ECO hubs......the exhaust brake info was relevant as I think it mitigates (mostly) one of my concerns with the eco hubs. Oil pumps and such have nothing to do with the hubs

Happy Holidays everyone!

 

[GeneralDisorder]

I don't think I have an oil pump issue but am definitely planning to add the filter between the HEUI pump and the head and would like to also add bypass oil filtration. I'll likely do my oil changes at 7500 miles for now, then likely extend that if I do install a bypass system.

Relative to the oil pump issue, shouldn't CAT be able to tell us what oil pump was used in the motor by the serial number? If you already have the revised style pump, no need to change it unless you are actually having a low oil pressure issue.

Now, back to ECO hubs......the exhaust brake info was relevant as I think it mitigates (mostly) one of my concerns with the eco hubs. Oil pumps and such have nothing to do with the hubs

Happy Holidays everyone!

The thread has 26 pages of ECO hub information at this point. If it drifts a bit it's pretty much irrelevant as the original discussion has already covered most aspects of note.

The oil pump has/had multiple design revisions and defects. The pump rotor (gear vs. gerotor), and the idler gear have both been changed and I suspect also the bypass valve spring rate. Having seen the oil pressure on a 3216b with a new pump compared to where mine runs and having done oil analysis that suggests likely (in my mind) idler gear bushing wear materials - I'm not taking any chances. It's on my short list. If I'm dropping the pan to inspect it I'm just going to replace it. Not worth the effort to put it back in. And a replacement engine from CAT is $55,000 give or take..... oil pump is CHEAP insurance.

 

[GCecchetto]

The thread has 26 pages of ECO hub information at this point. If it drifts a bit it's pretty much irrelevant as the original discussion has already covered most aspects of note.

The oil pump has/had multiple design revisions and defects. The pump rotor (gear vs. gerotor), and the idler gear have both been changed and I suspect also the bypass valve spring rate. Having seen the oil pressure on a 3216b with a new pump compared to where mine runs and having done oil analysis that suggests likely (in my mind) idler gear bushing wear materials - I'm not taking any chances. It's on my short list. If I'm dropping the pan to inspect it I'm just going to replace it. Not worth the effort to put it back in. And a replacement engine from CAT is $55,000 give or take..... oil pump is CHEAP insurance.

Out of curiosity, what kind of oil pressure did you see with the new pump in the 3216?

 

[GeneralDisorder]

Out of curiosity, what kind of oil pressure did you see with the new pump in the 3216?

@Lostchain reports ~40 psi at hot idle. My truck is ~22 psi at hot idle.

Before the oil pump change his pressure was below 20 psi - sometimes would not read on the gauge if it was very hot and he would get an oil pressure warning. His old pump looked pretty good just on a visual inspection - there was slight play in the idler gear bushing. We suspect the bypass valve spring was weak. His truck had about 6,000 miles on it when we changed the pump. My truck has 16,000 miles - but I suspect my engine has a newer revision of the pump being a 2008 and his being a 2003. The 3126 and the C7 use the same pump though since they are basically the same engine.

 

[MatthewWBailey]

@Lostchain reports ~40 psi at hot idle. My truck is ~22 psi at hot idle.

Before the oil pump change his pressure was below 20 psi - sometimes would not read on the gauge if it was very hot and he would get an oil pressure warning. His old pump looked pretty good just on a visual inspection - there was slight play in the idler gear bushing. We suspect the bypass valve spring was weak. His truck had about 6,000 miles on it when we changed the pump. My truck has 16,000 miles - but I suspect my engine has a newer revision of the pump being a 2008 and his being a 2003. The 3126 and the C7 use the same pump though since they are basically the same engine.

Can you post the part# for that new pump revision. My '04 has the exact same numbers with 12k miles. I'm at ~5psi ish at stop lights in summer.

 

[Lostchain]

20R-7247 is the Reman part number which was 683.82 with a 1026.03 core charge lol. They really want the old one back.

https://parts.cat.com/en/catcorp/20R-7247

 

[Wingnut13]

Wow, big price difference from where you got quoted. My local CAT dealer quoted like $1800 with a $600 core charge if I recall.

the job was easy enough that I decided to chance a used pump…. Which has worked perfectly and maintains 40psi with thinner oil. I was running 15-w40 and now 10-w30.

I don’t recall any issue I found with the pump. Could be the bypass spring. I still have it.

 

[GeneralDisorder]

Can you post the part# for that new pump revision. My '04 has the exact same numbers with 12k miles. I'm at ~5psi ish at stop lights in summer.

Yeah your pump is trashed. Check out this video on a 3126b pusher RV with 92,000 miles - and remember mileage is irrelevant because our engine's spin 1000 rpm faster at highway speeds (without ECO hubs) than this RV so wear rates on parts that have known design flaws are accelerated:

 

[MatthewWBailey]

Yeah your pump is trashed. Check out this video on a 3126b pusher RV with 92,000 miles - and remember mileage is irrelevant because our engine's spin 1000 rpm faster at highway speeds (without ECO hubs) than this RV so wear rates on parts that have known design flaws are accelerated:

Looks like I gotta job coming up then. Do you recommend the cat sourced part or aftermarket? I see some from GTE on eBay for $430

Wagner cat wants $1000 core charge see pic

 

[MatthewWBailey]

20R-7247 is the Reman part number which was 683.82 with a 1026.03 core charge lol. They really want the old one back.

https://parts.cat.com/en/catcorp/20R-7247

Maybe I'll offer them a deal(real estate) to sell their house and they'll give me a discount.

 

[Wingnut13]

Looks like I gotta job coming up then. Do you recommend the cat sourced part or aftermarket? I see some from GTE on eBay for $430

Wagner cat wants $1000 core charge see pic

I saw a lot of bad press on RV forums of questionable quality pumps from eBay. The one I found was a company out of TN? That scrapped school buses. Which of all CAT 3126 uses is probably the best case. Not idle time to speak of, generally on a maintenance schedule, and warmed up before starting in the cold.