shuddering on shifts

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KempoDavid

Registered
My car is shuddering when it shifts. How can I tell of it is the accumulators or the TC?

I think it is the TC because it does it at any shift, and mostly at lower RPMs.

I use Merc V. the fluid is filled, its not real new but it's still under 30k miles.

Although I had the 1-2 piston job done originally, this is not my original tranny so I don't know if it is done on this one.

So, how can I tell if I need a new TC?
 
There is only one way to tell if you have the updated accumulator piston for sure, and that is to drop the pan. I'm going to guess you don't. Although you have only 30,000 miles on your current fluid it is time to change it and the filter, and drain the TC. I would get the 1-2 and 2-3 done and replace the filter, and totally refill with Mercon V before I went for a new TC as it means dropping the tranny again.

Didn't they install a new one with your rebuild or used tranny ?
 
I agree, do the simple less expensive stuff first. If that Trans was just rebuilt they should have installed the newer parts in it. You can't get the old stuff, they have all been superseded.

At Trans shop can tell if it's the TC or not but that's additional costs. If it does come down to a new TC don't go with an off brand relined unit your local shop tries to sell you. Some will slip you a 12 inch vice what the car comes with 11.25 inch. I've personally seen this several times when a customer brings theirs in for a TC swap. They then end up having to by a new flex plate too. Then most will reline them with the same thin paper friction they came with from the factory. The factory TC also uses plastic thrust bearings inside the TC vice real bearings. Depending on your budget and plans I would personally go with a 04 Marauder/Mach 1 TC. It is built much better than the all the other 11.25s. Furnace brazed, real Torrington bearing vice the plastic besides several other upgrades. It stalls the same as your stock unit so there's no performance difference, just more reliable. If you are wanting to add some performance than this is the time to step up to a higher stall TC also. Let me know if you are interested, I have several choices.
 
As far as I know the shudder is a bad TC or fluid, more often fluid.

A bad accumulator only causes hard shift, not shudder.

Right?
 
KempoDavid said:
I use Merc V. the fluid is filled, its not real new but it's still under 30k miles.
Click to expand...

The service interval is 20K miles or so on the Mercon V.

Remember, the Mercon V was a 'fix', not a 'cure' for the 4R70W, particularly the earlier models.

Yes, if "fresh" Mercon V does not fix the TC shudder issue, you need a new TC(even according to Ford's TSB). Also it is important to properly diagnose the 'shudder' to be sure it is the TC. The shudder originates from the TC lockup clutch 'slipping and grabbing' usually right after shifting. As soft as stock Lincolns shift, it is felt as 'during' the shift.

One trick is to '2 pedal' the car. Accelerate normally but with the left foot lightly depressing the brake. This forces the TC to unlock and the shudder should be gone during the shifts. ;)
 
driller said:
One trick is to '2 pedal' the car. Accelerate normally but with the left foot lightly depressing the brake. This forces the TC to unlock and the shudder should be gone during the shifts. ;)
Click to expand...

If you just brush your foot across the brake pedal with enough force to make the brake lights come on.. but not enough force to feel the car braking.. it will do just what Driller stated above.

Thought some might confuse the depressing the brake pedal as a power brake type manuever.

If you wonder how little pressure it takes to activate the brake lights back up to a wall or your garage and you should be suprised at "how little pressure it takes" to make the brake lights come on.

The TC lock/unlock is triggered by the brake light/BOO switch.
 
To be honest... Mercon V should last beyond 20k miles... when I did my trans fluid changes on my mark and crown vic the fluid always looked really fresh at 25-30k miles. And there was minimal build-up on the magnet.

I think I am going with 35k on my next trans fluid change on the Crown Vic.

Then again both cars have coolers so that may be an important factor.
 
I will have to try the BOO trick... despite fluid top-off it still is the same shuddering.

It shudders not only when it shifts but also at other times. for example, if I am cruising at 70 on the hiway, foot lightly on the pedal, and I give it some gas (but not enough to downshift) it will shudder slightly, then accelerate. is that the TC locking up (and shuddering as it does)?

Maybe Lonnie is going to get a big chunk of my tax return...
 
KempoDavid said:
I will have to try the BOO trick... despite fluid top-off it still is the same shuddering.

It shudders not only when it shifts but also at other times. for example, if I am cruising at 70 on the hiway, foot lightly on the pedal, and I give it some gas (but not enough to downshift) it will shudder slightly, then accelerate. is that the TC locking up (and shuddering as it does)?

Maybe Lonnie is going to get a big chunk of my tax return...
Click to expand...

The TC will unlock to provide more acceleration - prior to downshifting for even more acceleration.
 
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