nba1341

Hello I have a crown vic 99 with a 4r70w transmission.

When over drive is off it shifts through the gears fine but when you turn over drive on it will not shift through all the gears once it hits 50mph it just revs and won't shift past there.

Does anybody have any ideas on what could be wrong? The transmission fluid needs to be changed it smelled a little burnt which I will be doing tomorrow but I feel this has to be something different since it shifts fine with over drive off?

Thanks in advanced

WannaBeGearHead

Sounds like your clutches could be going bad. I'm not sure why it doesn't work with OD on but works with it off. Are you talking normal driving or going full throttle with OD on?

But either way burnt smell isn't good and more than likely are going to need a rebuild.

EDIT: Sounds like the OD band or whatever is going bad. IIRC you don't go into OD until 50mph which is where you are having problems.

nba1341

Now is this something that can be fixed by dropping the valve body or would I have to drop the entire trans. For the next two months I would be fine w/o over drive but come then I have to make long highway trips and thats not going to be fun for gas mileage.

I'll be changing the tranny fluid and filter this morning and report back if anything changes from there.

WannaBeGearHead

No. To fix the OD you would need to crack open the case.

ctgreddy

sounds like clutches/seals are going out on you. how many miles are on it? if i'm not mistaken when you turn o/d off i think it ups the pressure a tad for more grabbing force, hence why it may shift fine with o'd offf but not on. sorry but you'll have to drop the trans my friend.

...edit...nevermind i think i'm wrong, i was thinking of when you shift to first it engages something extra to have more grabbing power, not when you turn o/d off. i'd still say that it sounds like seals or clutches are going out.

tbirdscwd

Sounds like a worn overdrive band

Hangwire

A worn OD band should feel very sloppy and slump/sag into gear. Flat out not shifting into OD may mean its totally shot.

nba1341

Changed the fluid (no metal shavings in pan or anything bad) and it shifts very nicely without overdrive on. Still won't shift into overdrive though with it on.

Will it be ok to drive the car as is for now?

The trans has 175k on it so I would rather just buy a used one and drop it in but won't be able to till december/janauary

WannaBeGearHead

Ya you're ok to drive it. Also, if you have 175k miles on the transmission I would really look into getting a new converter also.