DTC's 74, 85, 87

[joescj5]

I'd look them up myself, but I lost my login to the members forum after my recent re-format.

While driving today my transmission seemed to go into limp mode. Wouldn't shift out of 2nd gear. After a restart the transmission was shifting fine. The codes I just checked out were the 74, 85, and 87.

Could someone shoot me the description for these codes. I need to figure out what route I need to take in tackling this issue.

Thanks.

[gmctd]

Those are probably connector related - pull the several transmission connectors, check for oxidation, pinched wires, etc - the first DTC is your input speed sensor - bad connection gives same symptom as bad component - check your harnesses, first

[bcbigfoot]

85: is undefined ratio error
87: is high ratio error

All are trans. related and likely one of the two 20-30$ input/output trans. sensors or as gmctd pointed out a wiring issue.

[joescj5]

Finaly got my access back to the members pages so I was able to find the error codes. Now I just gotta fix them. They all might be related to the larger tires I just had put on. I am now running 255/85 R16's which equate to about 33 inches.

I have already started working over the major electrical. I crimped and soldered new ends on two cables (they had the cheezy bolt on replacement ends). I've cleaned all the battery terminals and will work my way through all the grounding straps. Once I have all the connectiond PM's I'll clear codes, and update again.

[Robyn]

With these rigs the first stop has to be checking all battery connections and grounds.
Be sure to check the grounds at the RH rear of the intake manifold and the body ground strap too.

A poor voltage reading can lead to all sorts of grief.
Be sure your getting 14.7 at the Alt terminal and fairly close at the batteries.
This can vary a little but if you are below 13.5 at the system level you can see wierd stuff happening.
As the wiring ages the long runs that have multiple connections can start to see resistance climb and voltages drop that can drive the ECM crazzy and you too.

With voltage up where it belongs the issues may go away but if they dont they can certainly be easier to diagnose.

Good luck and keep us posted

Robyn