4R70W shifting issue - TCCoA Forums
 
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post #1 of 12 (permalink) Old 05-20-2011, 02:02 PM Thread Starter
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4R70W shifting issue

A few weeks ago while driving to San Jose a random problem surfaced. I would be cruising along at a steady MPH and suddenly the transmission would down shift, but seems more like the OD is coming off.

Throttle doesn't affect it, it will do it whether I'm on the gas or have my foot off the accelerator.

Only does it with the OD on. Driving in the city with the OD off it doesn't happen. This is what makes me think it's not down shifting from 3rd to 2nd that it's the OD turning off.

Only happens about every 250-300 miles on the highway but it seems that when it does happen it will do it 2-3 times then disappear again.

Should I start with the MLPS? I was also thinking possibly VSS or PCM. The motor was just rebuilt (after the problem started) so I don't think it's melted wires or Dan would have noticed since he had the motor out and re-wrapped most of the wiring harness.

-Kelly
===================================
Fuelly
94 LX 3.8L NA : Daily Driver. 270k on chassis, 10k on motor.
90 35th Anniversary SC : Stored for the Winter.
Needs Harmonic Balancer, complete suspension overhaul.
WTB: 90 SC BHJ harmonic balancer
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post #2 of 12 (permalink) Old 05-20-2011, 09:05 PM
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Yup, start with the MLPS and then also check the TPS if needed.

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post #3 of 12 (permalink) Old 06-02-2011, 03:35 AM Thread Starter
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I changed the TPS and had to put a new IAC on too and didn't help. Time to dig a little deeper.

-Kelly
===================================
Fuelly
94 LX 3.8L NA : Daily Driver. 270k on chassis, 10k on motor.
90 35th Anniversary SC : Stored for the Winter.
Needs Harmonic Balancer, complete suspension overhaul.
WTB: 90 SC BHJ harmonic balancer
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post #4 of 12 (permalink) Old 06-02-2011, 08:46 AM
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Check the wiring harness that runs just underneath the front of the transmission.
Where the harness connects my insulation was about 1/2" short and couple of the wires were nicked from years of road debre. When 2 of them shorted my OD would turn off.
Reinsulate the wires "I used a vacuum hose" and has been just fine since.

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post #5 of 12 (permalink) Old 06-25-2011, 09:29 PM Thread Starter
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Edit: I was really tired when I posted this last night.

I still haven't had time or the means to get my car in the air to look at the harness under the car or check the MLPS or VSS. Hopefully this week I can find some decent ramps that will work.

-Kelly
===================================
Fuelly
94 LX 3.8L NA : Daily Driver. 270k on chassis, 10k on motor.
90 35th Anniversary SC : Stored for the Winter.
Needs Harmonic Balancer, complete suspension overhaul.
WTB: 90 SC BHJ harmonic balancer

Last edited by BlueEyes; 06-26-2011 at 09:26 AM.
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post #6 of 12 (permalink) Old 07-07-2011, 12:17 PM Thread Starter
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Well all attempts to get under my car failed. Even with it up on ramps (safest for me) I couldn't really reach anything I needed to. Ended up taking it to a new shop and they put it up on the lift.

First the transmission harness connector was totally caked with black grease. I managed to get that fairly clean myself but this guy totally cleaned it up, looks pretty new now. There were some loose wires in the connector and bare wires near the connector, also bare wires where the insulation had been rubbed off up along side the trans going up into the tunnel.

He looked at the VSS and there is trans fluid inside the connector. Not that I know anything about it but from what I saw on the VSS there is a seal that is supposed to keep the fluid out of it. So maybe the seal is bad? Anyway he thought it's more probable that it was just the exposed wires shorting and the fluid in the VSS connector skewing the signal than it is a failing component.

So he fixed up all the bad wiring and I ordered a new VSS. I got a MLPS also just to have for backup since mine is so old.

I should be heading back to Utah soon so will be testing it on a long drive soon.

-Kelly
===================================
Fuelly
94 LX 3.8L NA : Daily Driver. 270k on chassis, 10k on motor.
90 35th Anniversary SC : Stored for the Winter.
Needs Harmonic Balancer, complete suspension overhaul.
WTB: 90 SC BHJ harmonic balancer
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post #7 of 12 (permalink) Old 07-07-2011, 02:51 PM
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Question

All that funk at Rear makes me suspect Extension Housing to Tranny Gasket or Drive Shaft Yoke Seal? ... Is this thing losing Tranny Fluid ?

GET OFF MY LAWN~! ... & Let's not forget guys... There's still a dead Imaginary Ex-Girlfriend out there...
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post #8 of 12 (permalink) Old 07-07-2011, 03:33 PM Thread Starter
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No it's not leaking or losing fluid at all. The transmission was rebuilt about 4 years ago and everything is very clean still, it was just that connector that was trashed with grease which seemed weird to me because everything else was so clean. I guess when they rebuilt the transmission they didn't think it was very important to clean out the plug.

-Kelly
===================================
Fuelly
94 LX 3.8L NA : Daily Driver. 270k on chassis, 10k on motor.
90 35th Anniversary SC : Stored for the Winter.
Needs Harmonic Balancer, complete suspension overhaul.
WTB: 90 SC BHJ harmonic balancer
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post #9 of 12 (permalink) Old 07-07-2011, 03:48 PM
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They may have slimed the early MLPS to keep it from Flooding as the early ones were know to do - The nicest new MLPS's come with all new Connector Kit for your harness to keep that from happening.

GET OFF MY LAWN~! ... & Let's not forget guys... There's still a dead Imaginary Ex-Girlfriend out there...
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post #10 of 12 (permalink) Old 07-07-2011, 08:38 PM Thread Starter
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The MLPS I ordered is a Motorcraft and in the picture it shows it with the plug all disassembled, I guess that's the connector kit?

-Kelly
===================================
Fuelly
94 LX 3.8L NA : Daily Driver. 270k on chassis, 10k on motor.
90 35th Anniversary SC : Stored for the Winter.
Needs Harmonic Balancer, complete suspension overhaul.
WTB: 90 SC BHJ harmonic balancer
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post #11 of 12 (permalink) Old 07-07-2011, 08:44 PM
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Yeah that sounds like the nicer high dollar one w/new Gaskets & Connector, the works - As old as yours is (& mine was) that should be a good thing - Clips on damned MLPS Connector are brittle as hell.

GET OFF MY LAWN~! ... & Let's not forget guys... There's still a dead Imaginary Ex-Girlfriend out there...
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post #12 of 12 (permalink) Old 07-19-2011, 08:02 PM Thread Starter
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Well I had the MLPS and VSS put in at the same time last Friday and no more shifting issues so far. The new MLPS is firm and took the slop out of the shifter. Will be able to test on a long road trip very soon.

-Kelly
===================================
Fuelly
94 LX 3.8L NA : Daily Driver. 270k on chassis, 10k on motor.
90 35th Anniversary SC : Stored for the Winter.
Needs Harmonic Balancer, complete suspension overhaul.
WTB: 90 SC BHJ harmonic balancer
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