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

[rustyk]

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?

[DmaxMaverick]

Contaminated TPS with spray lube?

[greatwhite]

Any trouble codes?

[rustyk]

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.

[DmaxMaverick]

"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.

[DmaxMaverick]

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

[rustyk]

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.

[greatwhite]

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

4l80e will have codes in the TCM if applicable.

:)

[rustyk]

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

[JetBoater]

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.

[rustyk]

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.

[JetBoater]

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

[rustyk]

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.