Replaced 4L80 with reman, now DTC 85 Unknown Ratio Error.

[Shbennett1985]

2008 M1152 Rev B
-Original transmission was shifting fine, but slipping in 1st gear
-replaced with reman 4L80E for 1997 K2500 6.5 diesel with new torque converter
-now I’m getting DTC 85 Undefined Ratio Error and DTC 87 High Ratio Error
-have replaced input speed sensor, output speed sensor and tried known good TCM.

Anyone familiar with this or seen it before? Is there something incompatible in the civilian 4L80E and the humvee speed sensors?

Would switching to a stand along transmission controller be an option?

 

[Shbennett1985]

Update:

It turns out there is no reluctor ring present on the tail shaft assembly for the output speed sensor to read. In 4x4 civilian applications in the 1990’s, the 4L80E used speed sensor located in the tail shaft of the transfer case, and there is no reluctor ring for the humvee output speed sensor to read.

Some lessons we learn the hard way. Hopefully this can help others before they make the same mistake I did.



2008 M1152 Rev B
-Original transmission was shifting fine, but slipping in 1st gear
-replaced with reman 4L80E for 1997 K2500 6.5 diesel with new torque converter
-now I’m getting DTC 85 Undefined Ratio Error and DTC 87 High Ratio Error
-have replaced input speed sensor, output speed sensor and tried known good TCM.

Anyone familiar with this or seen it before? Is there something incompatible in the civilian 4L80E and the humvee speed sensors?

Would switching to a stand along transmission controller be an option?

 

[Retiredwarhorses]

The donor vehicle wasn’t a 4x4, it was 2WD….I've seen this happen on a few occasions.

 

[Mogman]

You have to be very careful when installing a civy transmission, there are a bunch of little stuff, like the 4L80 (there is no need to add the E as all 4l80s were Es)
But I degress, even the lockup solenoid is different for the 4l80s that had EPROMs in the TCM and the later units (used a different PWM frequency)
The reluctor in question is on the rear planetary, some of the early 4X4 transmissions did not have this ring as stated above, all the 2WD transmissions of this era had this ring, there are three output shafts, one 4X4 and two 2WD, none of the 2WD shafts will work as they are much too long.
And as I understand at one point they dropped that reluctor ring all together and the "hole" to mount the rear speed sensor is not even machined. (but have not confirmed that, just something I read somewhere)
One interesting thing is the "rear oil" transmission, the one with the wide spaced cooler fittings was not introduced to the civy market until 1997 but all the transmissions I have seen in HMMWVs have the wide spaced "rear oil" cases, although I don't remember if I have seen any legitimate 95,96 A2 trucks and would be interested in feedback on that!