Grand Marquis problem 4r70w

[swirlparanoid]

I recently bought an 02 Grand Marquis with 87k on it and am having a problem with the trans. At roughly 35 to 40mph there will be a slight flare as it shifts into od. (no problem at all if od is turned off) I have searched around and only found people with a 2-3 and 3-4 flare but im positive mine is 4-od. Ive read many complaints from those with the 3-4 flare and there seems to be very mixed answers, it needs rebuilt, needs a servo, band is worn, can be fixed with a tune, its normal etc. Any ideas on what it might be?

It has the original fluid right now although i did put a bottle of LG red in it.

 

[Roadkingnc]

Fourth is overdrive. If there isn't any codes you will need to take it out and take it apart and inspect for damage.

 

[eagle23]

With those miles on the original fluid, I'd change to Maxlife right away, doing several drain/fills, and driving a few minutes between each to make sure each gear change happens.

I'm a big fan of LG Red, but you may have introduced it a bit prematurely when the old ATF wasn't removed.

BTW you can safely double the LG dose, per Trav and LG themselves. I've done that on my 91 Ranger (A4LD) and it cured all kinds of issues that Mobil 1 synthetic ATF didn't touch. It took 50-100 miles to become effective.

My thinking is to try the above first. If it doesn't work, you haven't lost much money before going deeper. With some luck, that will do the trick.

Keep us posted!

 

[CharBaby]

In those generation of Gr Marq/Cr Vic's, there was some issues with shift flaring and tq.conv shutter. A drain & refill of DexIII/Merc with LG Red may help or only mask the issue for a while. Or the new MerconV or LV...IDK which your Marq required!

 

[Colt45ws]

I would do a Jmod and install a few sonnax valves into the valve body, namely 76948-12K pressure regulator and 76948-29K OD servo regulator along with a supertuff VB plate #K092
If you want I can get you the hole sizes I drilled in my '04. I love the way it shifts. I left the accumulator springs in it so the shifts are not overly harsh. I call them Drama Free™ shifts.

 

[buck91]

As mentioned above, fourth is OD for you. But the tc lock up is independant. Check for tc lock by lightly dragging the brakes when cruising in OD at low speed (45-50mph maybe), should see rpms rise a couple hundred. If not you have a tc lock up issue. Do you get any shudder when gently accelerating in third (30-50mph depending on rear end)? That is also frequently signs of tc lock and atf incompatibility.

Remember these trannies were spec'd for Mercon and updated to Mercon V to solve the tc shudder problemsso I would start with a good mercon v fluidand go from there. Also check fortc lockup as I already mentioned

 

[RF Overlord]

@ the OP: my 2000 Grandpa-mobile does the exact same as yours, but only if I'm being very gentle on the gas. If I'm accelerating at any decent clip, it doesn't do it. I'm going to go with it being a characteristic of the factory shift schedule tuning.

My Marauder doesn't do it, but it's modified a bit...

 

[swirlparanoid]

Originally Posted By: buck91
As mentioned above, fourth is OD for you. But the tc lock up is independant. Check for tc lock by lightly dragging the brakes when cruising in OD at low speed (45-50mph maybe), should see rpms rise a couple hundred. If not you have a tc lock up issue. Do you get any shudder when gently accelerating in third (30-50mph depending on rear end)? That is also frequently signs of tc lock and atf incompatibility.

Remember these trannies were spec'd for Mercon and updated to Mercon V to solve the tc shudder problemsso I would start with a good mercon v fluidand go from there. Also check fortc lockup as I already mentioned


Unfortunately i have no tach and its so quiet i literally have to have no cars around me and be on a smooth road to hear the flare up, so im sure i wouldn't be able to tell if it did the things you mentioned.

and no i haven't noticed any shudder.

I forgot to mention it will do the same thing if im around 40 with od off then turn it on. I believe it would be in 4th at that speed then locking up the tc when od is pressed???

 

[swirlparanoid]

Yes ive only noticed it at very slow acceleration. I rarely ever get above 40 with it so i really haven't seen if it will do the same at higher throttle.

It does say Mecron V on the stick and the previous owner said it was never changed (original owner) so it shouldn't have the wrong fluid. Im definitely going to get it changed soon, the Lubegard was only put in for possible benefits in the meantime.

 

[oldmaninsc]

Originally Posted By: swirlparanoid
I forgot to mention it will do the same thing if im around 40 with od off then turn it on. I believe it would be in 4th at that speed then locking up the tc when od is pressed???


No - when OD is turned off you are in 3rd gear. The lock up converter can and will engage in 3rd gear also.

 

[swirlparanoid]

Originally Posted By: oldmaninsc
Originally Posted By: swirlparanoid
I forgot to mention it will do the same thing if im around 40 with od off then turn it on. I believe it would be in 4th at that speed then locking up the tc when od is pressed???


No - when OD is turned off you are in 3rd gear. The lock up converter can and will engage in 3rd gear also.


Ahh ive got this all wrong then. I always thought od was when the converter locked up i guess ive been wrong all these years lol. I guess my problem is the 3-4 flare then.

 

[RF Overlord]

Originally Posted By: oldmaninsc
No - when OD is turned off you are in 3rd gear. The lock up converter can and will engage in 3rd gear also.
^^^This^^^

At 87k you're overdue for a change, even if the fluid "looks" good.

 

[spk2000]

I had a shudder in mine and had the fluid flushed and put in a Wolf Head brand synthetic that I had never heard of before. The Goodyear dealer highly recommended it and I looked it up and there were great reviews about it. Fixed my problem with around 120,000 miles.

 

[Colt45ws]

4th is the hardest shift for this trans. The timing has to be just right as it has to unlock one clutch (Forward) and engage the OD band. If the Forward dumps too fast before the OD band engages you get a flare like this as the transmission goes into neutral momentarily. If the Forward doesnt dump fast enough then what would happen is a sag like the transmission is trying to stop the car.
All the other shifts just involve bringing on another clutch (upshift) or dumping one (downshift). Simple.
On a related note, This is why a 4-2 wide open downshift is the 'trans killer' for these as it has to do this shuffle at high power. Its better to hit 'OD off' before doing a pass or do like I do and learn to roll into the throttle and make it do a 4-3-2 shift.
This is why Im a fan of the JMod to modify the fluid flow in the valve body to quicken the shifts.

 

[asand1]

My FILs f250LD had the 2-3 flare and he was quoted $3,500 for a new trans. The mechanic said it was toast. I pumped the trans empty through the cooler line, dropped the pan and cleaned it, replaced the filter, and flushed 14 quarts of merc VI through the trans.

Works beautifully now. I think the OE filter was so plugged that line pressure was down causing slipping.

Change the filter and fluid before doing anything else.