Transmission Shudder

[FAMOVER]

Hi,

Symptom:
The car shudders at low load under 55 mpg and if pressed at higher speeds may also shudder. No shuddering occurs in 1st or 2nd gear only 3rd and up.

Likely Cause:
Bad Spark Plugs or coils
Bad TC
-Open to other suggestions?

Troubleshooting accomplished:
I changed most of the coil and plugs except for 2 coils. I will change the final two before check spark plus and coils off the list. I also changed the fluid and man it was easy I just wish someone would have spent the 30-40 dollars and done it 50k ago. Neither of these repairs fixed the shuddering although the engine did run better after changing the lugs and coils.

Planned additional troubleshooting:
I will also attempt to remove the TC pin from the transmission wire harness to confirm a TC failure before going whole hog changing the transmission.

If the TC is the culprit:
So because I like to have an idea or plan for the worse case which is transmission replacement. Does anyone know which transmission 6F50 or 6F55 is the right transmission for a SHO? When I search ebay for a used transmission I find that they try to sell you basically any used Taurus transmission but that can't be right. Certainly the SHO has a slightly beefed up transmission. I have the 2012 Ford workshop manual for the SHO and I think it says in there which one is supposed to be the correct transmission but I wanted to ask on the FORUM anyway.

I realize this is no easy job:
The job is very detailed I know and will have to setup and scissor car lift to do it in a gentlemanly manner. Its worth it to me to change it myself using the workshop manual because I will know where I stand when it is done. I would also like to do a bunch of maintenance on other things that would probably not be done if I take it to a shop that just does transmissions (Paint, preservation, etc...). Also I dont really want to pay a fortune to fix this and its definitely not under warranty 150k.

 

[luigisho]

Make sure tire and wheels are balanced. Could be a driveshaft/cv axle/joint issue in addition to what you have posted. Have a shop check the easy stuff first.

 

[FAMOVER]

Make sure tire and wheels are balanced. Could be a driveshaft/cv axle/joint issue in addition to what you have posted. Have a shop check the easy stuff first.

The tires do need balancing and the half shafts need replacement but those kind of problems don't usually cause an abrupt shutter during acceleration.

This shutter is predictable in any gear 3-6 below 55mph under a high torque low rpm accel (i.e normal driving). Once above 55mph the TC must lock and everything is fine but you can make it shudder if you push in the throttle. I've taken to driving with manual control so I cant shift at a little higher rpm so the torque load is must lower and the shudder is minimized.

 

[SM105K]

Buy 5 quarts of tranny fluid. Motorcraft LV Mercon. Drain as much as you can from the transmission. About 5 quarts should come out.....Put 5 new quarts in and see if anything changed.

 

[SHOdded]

What year SHO btw? 6F55 transmission. Yes beefed up compared to tge 6F50, but I believe uses the same torque converter!

Did you completely exchange the trans fluid or single drain/fill. A minimum of 3x drain/fill is required to exchange out the old fluid. 4x is better.

I would check the map sensors for oil fouling, the backs of the intake valves for carbon buildup, and the pcv valve/separator for clogging. PTU fluid might be gunked up too.

The TC does fail but fairly rarely.

 

[FAMOVER]

What year SHO btw? 6F55 transmission. Yes beefed up compared to tge 6F50, but I believe uses the same torque converter!

Did you completely exchange the trans fluid or single drain/fill. A minimum of 3x drain/fill is required to exchange out the old fluid. 4x is better.

I would check the map sensors for oil fouling, the backs of the intake valves for carbon buildup, and the pcv valve/separator for clogging. PTU fluid might be gunked up too.

The TC does fail but fairly rarely.

Its a 2012 and I will definitely look into the PCV and MAP sensor that's a good idea. I guess when looking at the symptoms and how nasty the transmission fluid that came out was it seemed to fit. Also the fluid had been low when I checked it after getting home.

I will look at these things when I get home in a few days. Thank you for the suggestions.

 

[FAMOVER]

DO you know i

What year SHO btw? 6F55 transmission. Yes beefed up compared to tge 6F50, but I believe uses the same torque converter!

Did you completely exchange the trans fluid or single drain/fill. A minimum of 3x drain/fill is required to exchange out the old fluid. 4x is better.

I would check the map sensors for oil fouling, the backs of the intake valves for carbon buildup, and the pcv valve/separator for clogging. PTU fluid might be gunked up too.

The TC does fail but fairly rarely.

Do you know if the automatic AWD transmission for the standard Taurus 3.5L w/o turbo is the same transmission used in the SHO? I don't believe it is but if you search for a SHO transmission on EBAY it'll show you a ton of regular AWD transmissions and if you look in the description all the ones I looked at do not include the SHO so I'm inclined to think that the standard Taurus comes with an AWD version of the 6F50.

 

[SM105K]

From my research and having replaced one myself. All SHO's came with the 6f55.