The Mystery that is the 68RFE

BobSagetIsGod? said:
Whose driving an add a turbo truck at 7-800 HP on a stock 68rfe? That's simply not gonna happen.

Just talk with suncoast or Steve at commercial powertrain and get a replacement unit. That's really the only solution.
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I bet you're in that range with your s475. What'd you have to do to the trans, and how's it holding up?

If in the next couple years, they can nail down tuning and everything, I'll get pretty excited.
 
CorneliusRox said:
I bet you're in that range with your s475. What'd you have to do to the trans, and how's it holding up?



If in the next couple years, they can nail down tuning and everything, I'll get pretty excited.
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I have a stock transmission currently slowly dying every time I turn the key. I run the lowest tune I've got trying to preserve things as long as I can. Suncoasts mega68 holds my set up great on another guys truck. I will be visiting Calgary or Florida in the spring.


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Ive gotten over 3 years and 105,000km on my stock 68 in my 2012. Deleted since pretty much day one of buying it new, with hot dam tune and OD software. After the first year i did a second gen swap (s471) pushing 575-600hp with custom mcc tuning. Ran it that way for the following 2yr+, when overdrives finally failed late summer of 2015. I am pretty impressed with it considering i never babied it. I beat that poor transmission like a red headed step child, doing burnouts, countless amounts of 4wd boosted launches (always manual shifting). Little bit of towing here and there. I did have to replace the stock torque converter and flex plate though lol. Now i am running a 68 from commercial powertrain and i love it. Working great for me and i know of quite a few others that its working awesome for them as well (someof which have more power then me). I have fuel mods sitting at home to install so i am excited for this summer, have a goal of hitting 8-900hp, so we shall see. Might do compounds as well. Overall, i like the 68 for daily driving but it definitely does need good tuning imo! Still working in that for mine.
 
Can the adaptive learning ever be eliminated through tuning in a 68rfe I wonder?


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No, and I would not recommend it if it could. Just like the Allison the 68 has to be able to adjust the fill rates on the clutch packs. If you were to set them to a static value, you would have either really soft shifts all of the time which burns packs or really hard shifts all of the time which would be death on hard part components (input shaft for example). The issue is not the learning (the Allison and torqshift both have it and work fine).
 
phale said:
No, and I would not recommend it if it could. Just like the Allison the 68 has to be able to adjust the fill rates on the clutch packs. If you were to set them to a static value, you would have either really soft shifts all of the time which burns packs or really hard shifts all of the time which would be death on hard part components (input shaft for example). The issue is not the learning (the Allison and torqshift both have it and work fine).
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If you're going to the strip, is there any way to get it set to the nominal tuning? In my last Audi, I could remove the battery, hold the terminals together for a second, and it'd restart all of the 'learned' info. Since I DD'ed it, it had a lot of boring, stuck in traffic, old grandma settings that were learned.
 
If the adaptive learning could be disabled and hold/fill times calibrated and set to a static value, it would just have to be re-calibrated as the transmission wears. That wouldn't necessarily be "all the time". Deere power-shifts are done this way and can hold a calibration for a couple thousand hours of shifting up/down under load before needing a re-cal. I know it's apples to oranges but the principal is the same. I can see it being advantageous in a racing application.

Just a thought.
 
CorneliusRox said:
If you're going to the strip, is there any way to get it set to the nominal tuning? In my last Audi, I could remove the battery, hold the terminals together for a second, and it'd restart all of the 'learned' info. Since I DD'ed it, it had a lot of boring, stuck in traffic, old grandma settings that were learned.
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Re-flashing the truck wipes out the fill rates, but they just go back to a factory default. This is usually not a fast enough shift and if you hammer on it without allowing the fill rates to adapt it will in a lot of cases smoke the clutches. My best advice is try to drive the truck aggressively on the way to the track to get the shifts tightened up.
 
phale said:
Re-flashing the truck wipes out the fill rates, but they just go back to a factory default. This is usually not a fast enough shift and if you hammer on it without allowing the fill rates to adapt it will in a lot of cases smoke the clutches. My best advice is try to drive the truck aggressively on the way to the track to get the shifts tightened up.
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Do you know how long the adaptation lasts for (how many miles/hours back it logs from)?

If it's as easy as driving thirty miles with your foot to the floor, that's not too bad.
 
phale said:
Re-flashing the truck wipes out the fill rates, but they just go back to a factory default. This is usually not a fast enough shift and if you hammer on it without allowing the fill rates to adapt it will in a lot of cases smoke the clutches. My best advice is try to drive the truck aggressively on the way to the track to get the shifts tightened up.
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I noticed the tuning was not a 68rfe solution personally early on with having the 2nd comp68 back in 2010 or 2011 if I remember correctly suncoast was sending all the TCMS to Dave at B&G for tuning.... for what was a "race " specific tune. Then with time and more R&D they started and still use H&S for the tuning, but I'd put money on it that as has been said before...... if your not driving the 68 hard all the time it reverts back to softer shift schedules. There are time that the 68 can feel different just from a 20min drive hard to the grocery store, turn the truck off to go inside, and then bam it feels like a completely different trans.

I'm no expert, but every builder I've ever talked to say there are 2 main reasons the 68 is so up and down and this is due to 1. the communications between the ecm and tcm, and 2. the adaptive learning that is never ending.

Best advice on the 68 just find one style of driving you enjoy and avoid stop and go traffic.

If your racing it, then do as above poster says and make sure there are a few key cycles before you run down the track as it seems it recalibrates upon each start.
 
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blackmega3500 said:
I noticed the tuning was not a 68rfe solution personally early on with having the 2nd comp68 back in 2010 or 2011 if I remember correctly suncoast was sending all the TCMS to Dave at B&G for tuning.... for what was a "race " specific tune. Then with time and more R&D they started and still use H&S for the tuning, but I'd put money on it that as has been said before...... if your not driving the 68 hard all the time it reverts back to softer shift schedules. There are time that the 68 can feel different just from a 20min drive hard to the grocery store, turn the truck off to go inside, and then bam it feels like a completely different trans.

I'm no expert, but every builder I've ever talked to say there are 2 main reasons the 68 is so up and down and this is due to 1. the communications between the ecm and tcm, and 2. the adaptive learning that is never ending.

Best advice on the 68 just find one style of driving you enjoy and avoid stop and go traffic.

If your racing it, then do as above poster says and make sure there are a few key cycles before you run down the track as it seems it recalibrates upon each start.
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Agreed. I had the B and G tune on my stock 2008 68 for 60kmiles, 20+ sled pulls and plenty of miles with 20k lb trailer. All at 500+ at the wheels. I was actually more impressed with that than I am my fully built comp68 from suncoast.
When you consider all the issues and multiple rebuilds I have had with my comp68. I am at 700 RWHP but don't tow with it anymore. Considering I have $12k! into the trans its been a disappointment. Especially with not being able to control lockup as needed for racing.
I do the drive like a jackass before each race to get the shifts firmed up. If you don't it will smoke a clutch. You can't be running around at 400hp and then switch to 700hp without shifting through the gears 10+ times so the adaptive can catch up.
I agree the adaptive is way worse than an allison and ford. it seems to be set up to give grandpa the softest shifts possible. I wish I could have a switch to turn the adaptive off for racing.
If you have a stock trans and mild power put H and S overdrive on it and be happy...
 
It'd be nice to have a way to quick load some presets. That way it could be more responsive to changes. I know on my latest Hardway tuning anything over 20% tps will downshift 2 gears and unlock the converter. Which makes the truck fall on its face even accelerates to make the speed limit. I called to see if we could revise this and was told they can only control pressure, not shift points etc. Strange that it never acted that way with all the previous tunes.
 
Can you just get the tuning for the transmission from h&s? I already have efi live and don't need their engine tunes.
 
The H&S OD tune may not be the best thing out there, but it dang sure beats the schidt out of stock. Especailly with a trailer. $.02
 
Kick Start said:
Can you just get the tuning for the transmission from h&s? I already have efi live and don't need their engine tunes.
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I have never been able to get that done. I would love an xrt etc with just the overdrive tune for $400. xrt pro is 1200 +300 for overdrive. ummmmm he...ll no.
 
And whoever created this "adaptive learning" bull crap needs immersed in a bed of fire ants. I put put around all day to save fuel then it shifts like mush when I hammer it on the on ramp. Brilliant thinking.
 
Just a fyi; I run straight OD tuning with all settings maxed except line pressure. I've been running this way for years now and the results have been very positive. Last I checked, Suncoast was basically using the same tuning for the Mega units as I am, just in the form of MCC. My tuning never changes and I run mine on the 3200 pulse setting all the time. This may be why my trans seems to hold up so well...

I am also running a manual lockup Valve body.


As of current, Intermediate and output shafts are still stock, It's apparent they are solid enough to hold 1000+ HP as I have yet to break one.
 
So someone 'splain dis to me. I come from a long line of manual drivers and this is my first diesel auto so bear with me.

I'm sick to death of this downshift to 5th when I stomp it on the highway and wrap it to 3200 rpm bull crap. If a lock up switch were to be installed and turned on, that would keep it locked into 6th correct? How does that work exactly....I'm an auto dummy. I shouldn't need to downshift when running 1800 in 6th when I want to pass. It just wastes time and wraps the hell out of it.
 
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