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A General Fluid Flush Interval for Early A604's ?

2374 Views 8 Replies 5 Participants Last post by  valiant67
My '90 Grand Voyager just gave me its periodic transmission refill notice - 3rd gear lockout. Current mileage is around 148K, with 13,000 miles and 34 months since the last flush, with ATF+4.

A flashing light would be so much better than this method of communication, since it always results in an awkward moment on a high-speed roadway. And finding out what the specific condition is requires a visit to a dealership, one of which charged me for over an hour of shop time the last time I was curious enough to investigate.

Having looked through the volumes of communication on these early transmissions, I'm still not sure what the recommended service interval would be for fluid. Haynes says two years or 30K miles. I've seen 15K from more than one source. Driving this van about 5-6 K per year, I know that it doesn't leak, and that currently the fluid looks pretty clear. So, I'm wondering what the recommendation would be, and while we're at it, how do you flash one of these TCM's ?
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And if it's a 3.0 van, you could find a 3.0 5 speed manual car

KOG said:
We've done one 604 to 670 replacement. Easy, but you do have to get a 670 from a minivan, not one of the car versions. And you will want to rebuild it before installing. If it's a 3.3 you cannot use a 670, three speed never made with that bellhousing pattern, only fits 3.0.
And you could also do the same swap to a 5 speed manual providing it's a 3.0 powered van. You'd really need both a 4 cylinder 5 speed van for the shifter and pedals and a 3.0 5 speed car for the transmission.
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