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1995 4l80E suddenly lost OD and reverse.

Messages
3
Likes
0
Location
Arizona
Thread starter #1
I have a 1995 6.5 vin F, been shifting perfect, went to a buddys house today everything was fine I left and immediately noticed a shift issue, stopped and turn off the truck, restarted and got on the highway to see I have no OD, stopped a few times and restarted the truck while limping home (about 10 miles), hooked up to scantech and had a code for trans input speed sensor, fount it was unplugged, plugged in noticed no reverse and still no OD. trans never got above 160°F, any suggestions?
 

JayTheCPA

Well-Known Member
Messages
1,684
Likes
1,037
Location
Annapolis, MD
#2
If the OBD I systems are like the OBD II systems in terms of allowing OD, the ECM needs to see coolant temps above 130* F (as measured at the thermostat housing) in addition to trans fluid temps above 70* F.

Does the motor sound machine-gun like when the dash gauge indicates it is warm? If so, it might point to a bad ECT sending unit for the ECM.
 
Messages
3
Likes
0
Location
Arizona
Thread starter #3
engine sounds fine, scanner shows temps ate good, 1,2,3 shifts are normal, but no engine braking. I dropped the pan and there is a bit of clutch dust in it but no metal shavings, fluid didn't really smell burnt and its only been about 12k miles since I serviced it last.
 

WarWagon

Well it hits on 7 of 8...
Messages
8,522
Likes
3,138
Location
AZ
#4
Make sure the codes are clear and stay clear. It should code if it won't go into OD when commanded to do so. Undefined gear ratio codes mean something mechanical is broken. I think 4th and reverse are related to a single band, but, I am fuzzy on that.
 
Messages
3
Likes
0
Location
Arizona
Thread starter #5
Yep kept getting dtc 87, I'm pulling it out and ordering a reman seems as I have had too many issues with rebuilt trannys in the past. Thanks for the advice
 
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