48RE Trans - I Need Help!

[barry mitchell]

When the trans temp reaches 165, the speedo sweeps erratic back and forth, and then the trans doesn't shift correctly.

This only happens when the trans has reached 165 temps. there are no codes

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[AK Bob]

Not familiar with the 48RE transmission, but it sounds like a heat-related transmission control module issue.

Hopefully, others with more knowledge and experience with these transmissions will chime in shortly.

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[toyota_mdt_tech]

Just from the description, it might be as simple as a failed trans speed sensor.

Usually, it's just a small fine coil of wire and generates an AC signal as a pole piece, or reluctor wheel passes over it.

So if there is an open in this fine coil (keep in mind, it's been heating and cooling down for years), it's probably an open in the coil as it heats up and pulls apart.

A quick ohm reading will show it, but if it's cool, it may test OK.

Of course, this is a critical input to the trans controller (engine ECU), and trans behavior may be erratic without this input.

I think I'd toss in a new one.

Indeed, you will have a code; you have 2-speed sensors, input, and output.

Suspect its the output.

Input isn't used for speedo.

I suspect it is in the tail shaft housing area somewhere.

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