4L80E: Doesn't shift into overdrive...

I'm on the road on a short trip (120 miles) in the motorhome; due to traffic, I didn't put the selector into OD until about 1/3 of the way here. It usually shifts into OD at around 50-55 mph. Never did shift, stayed in 3rd.

I had the coach serviced a week ago, and it worked normally. The only messing around I did was to spray lube on the IP shaft, as it wasn't returning to idle like it should. That's normal now.

I checked the TPS, and it's secure.

Temps and performance are otherwise normal.

Any ideas?

Contaminated TPS with spray lube?

Any trouble codes?

I don't have access to a scanner at the moment.

It's possible I contaminated the TPS, but I don't think so as it's an enclosed unit.

"Enclosed" is far from "sealed". Most spray lubricants penetrate very easily, which is as most are designed to do. Some of them aren't "plastic friendly", as well.

Trouble codes aren't really relevant on a mechanical system.

The tranny was about a qt. low on ATF; that might be it. I have the Mag-Hytec pan, BTW.

Mine does throw basic codes.

I'll wait until I get home to mess with it.

May be time to put the voltmeter on the TSP...

Thanks for the tips, guys.

Quote:

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Originally Posted by DmaxMaverick

Trouble codes aren't really relevant on a mechanical system.

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4l80e will have codes in the TCM if applicable.

:)

I guess I did the right exorcism chant; the tranny operated normally on the 125 mile trip home...:D

Hi Rusty,
I am curious if your overdrive issue remains fixed.

I was returning from a long trip from Port Hardy at the top of Vancouver Island and lost my overdrive last week, just south of Campbell River. I was towing my boat without camper, and the tranny temp reached 220° so it was cooking. Lots of ups/downs and twisting pavement on that highway.

The overdrive returned once the vehicle cooled down and worked fine after I pulled off the Ferry.

I had the transmission flushed and currently have no issue... but wonder if I need to be concerned the next time I go on a long haul.

I did my monthly 20 mile "exercise drive" a few days ago, and all was well.

A tranny temp of 220° is not excessive.

The stock torque converter is known to be weak, which is why I had a Suncoast Converters unit installed - the stock one failed, and although it would shift into OD, the temp ran around 180° up from the usual 145-150°, and also raised the engine coolant several degrees.

So to answer your question, it depends. I'd monitor the temps and see if there's a trend. I have the same basic drivetrain you have (no chips) - the stock 4L80E is good for 450 lb.-ft. of torque, so if your engine is uprated from the stock 190 HP, there's a very good possibility the TC is failing.

Noted with thanks.. will monitor for sure.
Cheers! Mike

Looking for something else last night, I found the Suncoast invoice - the HD torque converter was ~$1,300 and the machined spline was ~$600. They also rebuilt and upgraded the tranny itself, now rated at 850 lb.-ft.