OD Question on 4R70W

[miamibob]

Do you get better CITY gas mileage turning the OD OFF or putting it on? Should OD only be used for Highway driving?? I am asking about a 1995 Mercury Grand Marquis.

[sly]

you might get better mileage with OD on, but you'll get better life with OD off in town. search for torque converter shudder and you'll find out why.

[miamibob]

Why I ask is that checking the Digital Dash reveals between 11 and 12 or 13 MPG's in the City (A/C usually on). EGR ports have been cleaned in addition to new plugs/wires/air and gas filter replacements. Checked tires for excessive heat (dragging) so was wondering if I should leave the OD off as most of the driving is City. To me, those MPG's are pitiful!

[sly]

there's something else wrong then. check all the plug wires to make sure they are pushed down all the way on the plugs. I drove a 95 mgm one time at a dealer that had 3 plug wires barely touching. It ran like a top, but didn't have a lot of grunt. Got back, popped the hood and found the loose wires. Also, if you check them while the engine is warmed up, they won't pop back out due to air pressure buildup as sometimes might happen. I've had that issue on the 93.

That car should get at LEAST 17mpg around town unless you're doing a TON of idling.

[miamibob]

Has plenty of "pep" but checked the wires both at the plugs and coils. They are completely in so we must have another issue.

[sly]

I wonder if the TC is already going out and it's just not transferring the torque to the trans as well any more.

[gadget73]

The shudder problem is usually fixed with a fluid change to Mercon V isn't it ? And does the 4R trans do lockup in 3 and 4, or just 4? I know GM transmissions will do 3 and 4 both locked and unlocked depending on running conditions. I've never looked that far into the 4R's control logic.

[miamibob]

Trany was rebuilt less than 3K ago but one never knows, do one? Shit MPG before and shit now! Shifting seems good. Think I'll have the Dealer check it out unless I hear something good.

[sly]

The shudder problem is usually fixed with a fluid change to Mercon V isn't it ? And does the 4R trans do lockup in 3 and 4, or just 4? I know GM transmissions will do 3 and 4 both locked and unlocked depending on running conditions. I've never looked that far into the 4R's control logic.

in my 93... the shudder was due to completely worn out clutch plates in the TC's lockup. When it was replaced... the TC died in 4 days and the second TC got the job done and is the one that Scott replaced recently (and is probably still good).

[zoomie]

im wondering if youve checked your o2 sensors latley, those if they are broke,will make the car get bad mpg too

[miamibob]

im wondering if youve checked your o2 sensors latley, those if they are broke,will make the car get bad mpg too

Thought of those and as I mentioned, in another thread, I replaced all 4. Maybe 11-12 mpg City is all this car is going to get. No check engine lights/codes. Starts and runs smooth so I am at a loss......

[sly]

every time I've seen this problem... it was the torque converter or pump that was leaking internally like a sieve.

granted, that's only been about 4 times.

[miamibob]

every time I've seen this problem... it was the torque converter or pump that was leaking internally like a sieve.

granted, that's only been about 4 times.

Always possible but not detecting any slipping and the MPG's were about the same before the rebuild.

[sly]

ah. then I dunno. You gotta stumper there.

[zoomie]

call alan at dirty dog he specialises in the 4r70w trans-link in sig