vibration on acceleration

[hathomas]

1998 windstar, fine at low speeds but at 70 KMPH and up vibration through veichal. goes away when accelerator is not pressed. Have had over $3000 worth of front end work done by dealer who says there is nothing wrong , live with it. the last time he replaced serviceable front axels, ($1500) and no difference. Anyone have any auggestions? Oh I have 135000 KM on it and it has been doing this for the last 25000 KM or so.

[tidalcock]

I would have the dealer look at the transmission and torque converter. Also, insist that a qualified transmission service tech ride with you!

[pstubler]

How are the front bearings? If they are going, you can get shudder during high torque shifts (especially between first and second).

[ModMech]

Flush the Trans, and use Mercon V fluid. The Torque Converter is "shuddering", a flush and re-fill will usually cure this but you MUST use ONLY Mercon V ATF.

[lewisnc100]

Originally Posted by ModMech

Flush the Trans, and use Mercon V fluid. The Torque Converter is "shuddering", a flush and re-fill will usually cure this but you MUST use ONLY Mercon V ATF.

Check your owner's manual before you put Mercon V in, 1998 was a crossover year for Mercon to Mercon V and the Ford application chart shows some 1998 models with the AX4S (AXODE) transmission taking Mercon and some taking Mercon V. Also check your fluid level, could be low.

[BMW_4.4i]

Originally Posted by hathomas

1998 windstar, fine at low speeds but at 70 KMPH and up vibration through veichal. goes away when accelerator is not pressed. Have had over $3000 worth of front end work done by dealer who says there is nothing wrong , live with it. the last time he replaced serviceable front axels, ($1500) and no difference. Anyone have any auggestions? Oh I have 135000 KM on it and it has been doing this for the last 25000 KM or so.

Sounds like a typical Ford problem!

[rodeo02]

If you are getting the vib only at higher speed while the engine is under load, I would definately suspect a powertrain rather than a suspension or tire/wheel issue. It could be an engine mount or exhaust system hanger problem though I've seen a tight hanger or loose mount cause vibs. Torque converter shudder typically happens only on take-off, so I doubt it's that. Will it still vib if you take it out of 4th gear (OD) at that speed? You would get a CEL if the vib is caused by an engine misfire or perfomance problem. You definately don't want to keep replacing parts with out pinpointing where the problem is. As you've seen, many shops (especially dealers) are more than happy to "troubleshoot" by putting new parts on your van. Hope you get it solved.
G/luck
Joel

[Hooter]

I have a 1998 Windstar with 112K miles that seems to have a similar problem. The fluttering is most noticible under a load while accelerating. I had the transmission fluid changed but it may have not been the Mecon V. I notice also that the problem arises only when the engine has reached normal temperature, not when it is cold. I am open to other suggestions and hope that I don't have to do a transmission rebuild.

[rodeo02]

Hooter- you need to make sure you have the merc 5 in there. Many shops still insist on using univeral ATF, or will use an "additive" which will supossedly make an ATF merc V compatible. This is no good for the 1997+ AX4N,AX4S. Has this unit been maintained regularly (atleast 1-2 pan drops by now?) IMO- these units are best suited for pan drop & filter changes as opposed to just a fluid swap or "flush". At his point, I'd do a pan drop & filter change which will change out more than half the ATF you have in there. See if that helps.
G/luck
Joel

[ModMech]

Ok, a couple things here.

1) T/C shudder NEVER occurs when "taking off" with a late model ('93 up) Ford electronic AT. Why? Because the T/C is "open" or unlocked in 1st, so it CANNOT shudder in first. Note: Older mechanically locking T/Cs did shudder in 1st more than any other gear.

2) Torque Converter (T/C) shudder is caused by the ATF being broken down, and calsium deposits on the T/C clutch facings causing it the grab and slip alternately.

3) TWO things you can do to preven shudder: a) Keep fresh ATF in it (Mercon V ONLY '98up); b) Keep it COOL. This means on a WS, proper cooling system maintence because the ATF is cooled by the engines radiator. The hotter the radiator is, the hotter the ATF.

4) Shudder feels like you are driving over "rumble strips".

5) Our '98 was improperly filled with regular Mercon, it began to shudder about 10,000 miles afterwards. Since then, it has had a complete transfusion of Mercon V fluid (11 qts), and it went away almost immediately. I could not believe how much better the trans shifted in every gear after the correct (mercon V) fluid was in.

5) You MUST NOT use "Mercon V" fluid in older (pre'98) FWD transmissions.

I should also note that in our '98 the shudder was most apparent pulling a slight grade at steady throttle, or under slight acceleration. You could also feel it on the moderate throttle 3-4 upshift, but you'd need to be very aware of the vehicle to notice it then in our case.

Also, the T/C is in "lock" in 3rd, and 4th unless the throttle is closed, wide open, or the brake is depressed. In any of those situations, the T/C is unlocked.

[Hooter]

Originally Posted by Hooter

I have a 1998 Windstar with 112K miles that seems to have a similar problem. The fluttering is most noticible under a load while accelerating. I had the transmission fluid changed but it may have not been the Mecon V. I notice also that the problem arises only when the engine has reached normal temperature, not when it is cold. I am open to other suggestions and hope that I don't have to do a transmission rebuild.

OK. I have now replaced the transmission fluid with Mercon 5 but no real measureable improvement. However, thinking that this is somehow related to the engine, I find that when I fill it up with premium gas, the pulsation is much reduced. Is this possibly an engine timing problem that occurs upon warm-up but is reduced using higher octane fuel?