C6 with overdrive unit
Fleet Mechanic
Joined: Aug 2007
Posts: 1,508
Likes: 2
From: The boonies by Dallas OR
So why is the C6 harder to kill behind a diesel?
The C6 didn't have lockup, right? That would make it hot as heck all the time.
Isn't the back end of the E4OD very similar to the C6, with a overdrive planetary and clutch set at the front? So why the disparity on the reliability.
And why the far more expensive repairs on the E4OD vs. the C6?
The C6 didn't have lockup, right? That would make it hot as heck all the time.
Isn't the back end of the E4OD very similar to the C6, with a overdrive planetary and clutch set at the front? So why the disparity on the reliability.
And why the far more expensive repairs on the E4OD vs. the C6?
Freshman User
Joined: Feb 2005
Posts: 25
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I've got one for sale
I have a freshly built c6 with a US Gear 30% manual overdrive behind it. Never been driven. For sale. I'll have to dig up the receipts to see what I have in it. The overdrive was not cheap.
Frmr Ford Trans Engr
Joined: Aug 1999
Posts: 24,705
Likes: 2,626
From: SE Florida
I haven't seen any evidence that this is true.
They did run hotter, but they also had larger coolers because they did not have lockup.
Two reasons. First, Ford cost reduced a lot of things that went into the E4OD. That never helps reliability. Second, electronics in transmissions were brand new, in fact the E4OD was Ford's first electronic transmission. The electronics caused some of the problems. Both of these problems were largely solved in later years.
Electronics are not cheap, and there are a lot more parts in an E4OD than a C6.
Electronics are not cheap, and there are a lot more parts in an E4OD than a C6.
Fleet Mechanic
Joined: Aug 2007
Posts: 1,508
Likes: 2
From: The boonies by Dallas OR
I wonder if that's the key right there? There are times that the E4OD can make a whole lot of heat. As people know, the cooler folks were very stingy with the cooler for the E4OD. The C6 may have run hotter most of the time, but the peak temp for the C6 would be lower with that bigger cooler.
Posting Guru
Joined: Oct 2005
Posts: 1,017
Likes: 3
From: Longwood, Fl
Maybe MK will agree with me--. The is no inherent reason for either to run hotter than the other if none of the internal clutch packs are slipping. Most of the heat that is created in a normally functioning tranny (C6 or E4OD) is created by the slipping of the converter. In lockup, the E4OD has no slippage and will run cooler than the C6. The lockup feature of the converter is not manually controlled, so a smaller cooler is needed. Lockup occurs regardless of what you are towing. You can lockout OD, but not lockup.
I have not seen any figures (you know of any MK?) that suggest an E4OD converter creates any more heat when unlocked than the C6. It can create lots of heat if the converter clutches are slipping in lockup.
I have rebuilt several C6's and am in process on an E4OD now. The E4OD, like the AOD when it was introduced, had some teething problems, but now parts are available that pretty well take care of that. I may get in trouble over this, but I like the E4OD much better.
I have put low gear sets in the C6 and bolted on an OD unit, still like the E4OD. My .02 anyway 
I have not seen any figures (you know of any MK?) that suggest an E4OD converter creates any more heat when unlocked than the C6. It can create lots of heat if the converter clutches are slipping in lockup.
I have rebuilt several C6's and am in process on an E4OD now. The E4OD, like the AOD when it was introduced, had some teething problems, but now parts are available that pretty well take care of that. I may get in trouble over this, but I like the E4OD much better.
I have put low gear sets in the C6 and bolted on an OD unit, still like the E4OD. My .02 anyway
Fleet Mechanic
Joined: Aug 2007
Posts: 1,508
Likes: 2
From: The boonies by Dallas OR
True, the E4OD doesn't generate any more heat than the C6. But with a little cooler, the E4OD will get a lot hotter when generating the same heat.
When highway towing, the E4OD stays reasonably cool.
But lockup doesn't occur in 1st or 2nd below 2/3 throttle. Drive steep back roads and the transmission will overheat.
Backing a heavy three axle 5th wheel or gooseneck will heat the heck out of the transmission. Lots of weight on the truck so it doesn't roll easy, plus the scrub of sliding the trailer axles means better than 1/2 throttle to move on flat ground in a turn. Add any slope and it's even more. With a stock cooler, it's under a minute to hit 240°F on a engine and transmission starting out at operating temp.
The truck says GCWR 20,000, but try 20,000 with a stock cooler and the transmission fries way to early.
When highway towing, the E4OD stays reasonably cool.
But lockup doesn't occur in 1st or 2nd below 2/3 throttle. Drive steep back roads and the transmission will overheat.
Backing a heavy three axle 5th wheel or gooseneck will heat the heck out of the transmission. Lots of weight on the truck so it doesn't roll easy, plus the scrub of sliding the trailer axles means better than 1/2 throttle to move on flat ground in a turn. Add any slope and it's even more. With a stock cooler, it's under a minute to hit 240°F on a engine and transmission starting out at operating temp.
The truck says GCWR 20,000, but try 20,000 with a stock cooler and the transmission fries way to early.
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Frmr Ford Trans Engr
Joined: Aug 1999
Posts: 24,705
Likes: 2,626
From: SE Florida
The manual does not say to shut off the overdrive with heavy loads. It says to shut off overdrive if the trans is frequently shifting in and out of overdrive.
Posting Guru
Joined: Oct 2005
Posts: 1,017
Likes: 3
From: Longwood, Fl
I dont think the E4OD locks up by throttle position, unless it is earlier under no load conditions. Mine locks at ~45 with my foot to the floor. By then it is in 2nd. I have noticed that it is at a bad time because it is usually in the low end of 2nd. When leaving a toll both with an 8K boat, while trying to get up to speed to get to the merge back to 2 lanes (4 lane hwy), it is a very bad time to lose all that ratio. The lockup itself loses about 700-800 rpm in addition to just shifting to 2nd.
Thats why for those conditions, I would like to delay lockup, with a switch, until I reach road speed. Lots of discussion already about installing a switch on the converter clutch solenoid. I will try that! Also add a very large cooler.
Thats why for those conditions, I would like to delay lockup, with a switch, until I reach road speed. Lots of discussion already about installing a switch on the converter clutch solenoid. I will try that! Also add a very large cooler.
Fleet Mechanic
Joined: Aug 2007
Posts: 1,508
Likes: 2
From: The boonies by Dallas OR
The throttle based 1st and 2nd lockup is only noticeable if you have a heavy enough load on a hill. Without enough load, you won't stay in 1st or 2nd long enough to notice it because there is a time delay of about 30 seconds once the revs are high enough. It will lock up as low as 15 MPH in 1st. It's really noticeable because the revs drop so much. Drops from something like 2800 down to 1900.
It is useful for controlling heat on steep, curvy roads. Rather than let is slip at a constant 1/2 to 3/4 throttle, you can get on it and make the TC lock up, then back off to check speed if necessary as you come up on corners.
It is useful for controlling heat on steep, curvy roads. Rather than let is slip at a constant 1/2 to 3/4 throttle, you can get on it and make the TC lock up, then back off to check speed if necessary as you come up on corners.