[lexingtonNW]

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 ?

 

[KOG]

About 10-12 years ago I started putting drainplugs (1/8" metal roofing screws) in every 604 pan. Then I change the fluid every year. Takes exactly 1 gallon for refill and less than 15 minutes of time when changing engine oil. I've had to replace two torque converter clutches and no other transmission parts since then.

 

[ImperialCrown]

If the ATF is full and fairly clean still, then I think that you will need more than a fluid change to get it out of limp-in. There is a fault code stored in the TCM that will help us determine the reason.
There were other scan tools (Snap-on, OTC, etc) that can read OBD 1 Chrysler codes. The dealer can't justify going over the base diagnostic charge just to read fault codes. Call around.
You will need a dealer for a TCM flash if one is possible. TCM's weren't flashable until 1994. Yours may not be original. Flashable TCM's are recognizable by the cooling fins on the housing. There may be an authorized software update sticker soft_label.gif on or around under the hood if the flash has been done. The latest software (4761847AA for the 3.3L equipped transaxle) was released late 1995. The new software may a huge improvement in shift quality and was less prone to faults. If you don't have the newer style, you will need one and it may have the latest flash in it.
ATF change intervals will vary by duty and conditions. It really doesn't sound like you need new fluid at this time.

 

[KOG]

And, as usual, I agree with Imperial Crown. Regular fluid changes are a good idea, but I don't think you're going to solve your present problem that way, too late.

 

[lexingtonNW]

Thanks for the quick replies. My inclination, if I wanted to try and keep this thing long term, would be to skip all the electronic pitfalls and look into a manual conversion. But I don't think there are too many flywheels available out there.

 

[ImperialCrown]

Stick-shifts were very rare, even when these were brand new and only available with the 2.5L 4-cyl.
It would still be nice to know what the stored fault code is in order to know how bad the situation is. A fault code is a good starting point. (Some fault codes were 'cured' with the TCM software flash described below.) Then decide what to do.
This is the TSB for the TCM reprogramming update: http://www.robskorner.info/faqs/TSB/18-24-95.pdf

 

[dak4x4]

Another thing to consider is replacing the tranny with the more reliable 3 speed, these should be plentiful in salvage yards.

 

[KOG]

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.

 

[valiant67]

And if it's a 3.0 van, you could find a 3.0 5 speed manual car

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.