Mopar minivan trans question

Looking at a '91 Caravan swb with the a604 trans. I've driven it and it shifts fine 1,2,3 (no slippage)but 4th is out. Reverse works fine. Seller says 4th went out a few months ago and he since put in new speed sensors but they didn't help. I know many of the Mopar trans from this gen have bad reputations some deserved some not. If I did buy it (the price is right), I'm thinking on doing a full trans flush and maybe a new solenoid pack (if I can find decent priced). Am I thinking properly in terms of remedying this problem? Or shall I start somewhere else? Seller says he has run the correct Mopar +4 trans fluid since he's had it (about 3 years) but he isn't sure the guy he bought it from didn't use Dexron/Mercon.

Or could this be a reason to pull out the auto trans and swap in a 5 speed manual?

Oh it's got the Mitsu 3.0 6g72 mill which still runs decent. It's a 100% stock van no mods whatsoever.

I can't answer your initial questions, but I'm fairly certain no van came from the factory with a Mitsu motor and a manual transmission, only the MoPar engines.

Still, you can get the pedal cluster from a stick shift van (although they are quite rare) and I'm sure there are several manual transmissions that will mate to Mitsubishi blocks, but it will likely still stick you with ordering or building custom axles.

The manual comment was off the cuff. But I do recall reading the A543 5 speed can be made to work w the 6g72 engine AND the a604 axles.

But if 4th gear aka overdrive can be resurrected in the a604, that would be first choice for the sake of immediacy.

Weren't those early 4 speeds known to have a lot of problems? A quick google of the losing 4th gear doesn't bring anything up though, so it could be something stupid (OD switch, bad temp sensor making it think it's super cold, etc.). I'd be surprised if it can't be 5 speed swapped with some combination of K car crap, I know could get a 3.0/5 speed in the cars.

I'm fairly certain no van came from the factory with a Mitsu motor and a manual transmission, only the MoPar engines.

No, they didn't come that way. I built one, though. 3.0/5spd van swap thread

As far as the 604 trans goes, what's the condition of the fluid? If it's dark and burned, you've got internal problems, end of story. IF it doesnt smell and isn't dark, you may have a problem you can fix from the outside. A scantool that will hook up to the old obd1 chrysler transmission connector (blue, under dash near steering column) would really help. Those transmission controls were very advanced for the time and would give you the time it took from solenoid application until it detected that the clutch actually grabbed from the change in the speed sensors. It would also give you a ratio error (slip) code if input and output speeds didn't match the ratio of the desired gear. Of course you could get a basic open/shorted solenoid code too. Lots of help to be had from the computer if you can find an old scan tool that hooks to it.

Other than that, you can swap out pretty much all the electronics on the trans for ~$100, but it's a shot in the dark. 4th gear is super weak mechanically in those transmissions and there's a decent chance it's failed mechanically. I would make damn sure the fluid doesn't give any sign of an internal problem before dropping money on a solenoid pack and input/output speed sensors.

In reply to Vigo:

Totes could come with a 6g72. 2.5, the old 12 valve sohc 3.0 mitsu and 3.3.

The 3.3 was the best option. Now that said, all this means is OP should scour a junkyard for a dual cammer and five speed to put in it for funsies.

E: Nevermind I reread what you wrote and it registered the second time.

Grizz wrote: In reply to Vigo: Totes could come with a 6g72. 2.5, the old 12 valve sohc 3.0 mitsu and 3.3. The 3.3 was the best option. Now that said, all this means is OP should scour a junkyard for a dual cammer and five speed to put in it for funsies. E: Nevermind I reread what you wrote and it registered the second time.

I'm confused by this. In 91 this van would have had 3 engine/trans options 4 if you count AWD.

Chrysler/Mitsu 6G72 3.0 V6 SOHC/Auto

Chrysler 8V SOHC 2.5 4 cyl/Manual

Chrysler 3.3 OHV V6/Auto FWD or AWD

No he was saying you couldn't get the mitsu engine with a manual, which is true. First time I thought he was saying they didn't come with a mitsu engine.

I had a 93 Caravan w/ the mitsu 3.0-it is a great motor. I'm pretty sure those trans did not have a 4th gear, but they did have a lockup converter. Mine went out, so it was only 'technically' a 3 speed. I lost maybe 1-2 mpg because of this but drove it another 50K miles. Maybe, that is the problem? Not a deal breaker if the van is cheap enough.

Yeah, I had a '92 base Caravan with the Mitsu 3.0 and it was most definitely a 3-speed with a lockup TC, not a 4-speed. Given that the revs dropped a tad when the convertor locked, I could see that a person might think it was a 4-speed. I bet the lockup solenoid cashed in its chips.

3.0 could get either 3spd or 4spd. It's extremely easy to tell just by looking at the gear indicator on the dashboard, but other clues in the original post make it pretty clear this is one of the 4spds.

I agree that the 3.0 is a great motor. Tragically overshadowed by its more glitzy and massively less reliable DOHC cousin (3000gt et al).

Recent pic of the 3.0/5spd van I built for a friend. The burnout marks are.. fresh. All 140 hp worth.

Good thing this isn't my dd (yet). Finally got in for a good look, 4th gear clutch pack is burnt up.

So reading through the 5 spd swap link above, I have a few questions. If they were already addressed and I missed them please forgive me. Did you need new axles for this swap? If so what did you use? What computer issues did this swap create? How were these "solved" if it came to that? I'm pretty sure I wouldn't be able to find van specific shift cables, so what did you use?

In an aside I found for sale locally a 5 speed manual from an '03 Eclipse GT, which for this model year shows the only engine option to be the 6g72 3.0 v6, which is what I have in the van. Even though on paper they appear to be the same engine, I realize there could be some odd duck reason that would prohibit using this particular trans?

And you saw how tiny the 4th gear clutch pack is, eh?

There's a lot that goes into an auto-to-manual swap. I've done 5, two of them being on dodge minivans. In this case, you don't need new axles. You DO need to weld on a bracket for a 4th motor mount which doesnt exist in an auto-trans van. You can adapt shifters, shift cables, clutch pedal, and clutch cables from other vehicles. The van pictured above was done entirely out of a parts stockpile i already had (other than the trans itself). Because of that i was able to compare all the parts I had and pick the one that looked like it would work best even though i couldnt remember which long-gone parts car it had come from. Occasionally a full 'minivan 5spd swap parts package' will come up for sale on one of the forums associated with these cars, and if you have the option of buying something like that i definitely would.

The computer issues are pretty minor. There are some differences in how the auto computer handles idle control, and the 5spd computer has a 400rpm higher rev limiter. Disconnecting the electrical connectors from the auto trans and simply leaving them unplugged won't create anything more serious than some stored codes. The only electrical issue you MUST deal with is that the starter relay grounds through the neutral safety switch (or transmission range sensor) and without that the car won't crank. All you need to do is find that wire and ground it. These vehicles never had a clutch switch so they will crank any time you want to try whether the clutch is in or not. This is useful for rolling a broken down Dodge onto a car dolley by simply cranking it in gear!

As for the eclipse stuff, it shares almost nothing. The Eclipse used a 24v version that, while still SOHC, used a totally different top end. The eclipse trans is a mitsu piece that won't swap into an old Caravan without requiring you to be the trailblazer with custom fab work.

It's gonna be rebuild time for sure. The trans (and rest of the van including engine) appears original with never a rebuild, 206k on the clock. That's probably pretty commendable for early 90's Chrysler technology? Especially for the new at the time (1991) a604 trans.

Unless I have yet to find the info that spells it out, it appears there is little in the way of mechanically strengthening this trans. But if there is, a spendy aftermarket controller would be needed.

I never mentioned the intended use of this van, but it's pretty much basic transportation with a fair amount of freeway driving. Any hopes of going fast or having much fun will have to be saved for another vehicle.

And thanks also for the Eclipse info Vigo. It's too bad a fair amount of their stuff doesnt easily interchange in this case.

I think the later 604s were improved somehow, my parents had one in a 4500lb AWD 1997 Grand Caravan that took a fair amount of abuse (towing 4000lbs*, running on mostly dexron, blowing an aux cooler line at 70mph and losing a lot of oil) before it crapped out the lockup clutch at 180k, and then kept going with just a new converter.

EDIT: *Mostly in overdrive.

BrokenYugo wrote: I think the later 604s were improved somehow, my parents had one in a 4500lb AWD 1997 Grand Caravan that took a fair amount of abuse (towing 4000lbs, running on mostly dexron, blowing an aux cooler line at 70mph and losing a lot of oil) before it crapped out the lockup clutch at 180k, and then kept going with just a new converter.

I should specify I'm talking this gen a604 (1st gen?) Yes that later ones likely held together a lot better.

drainoil wrote:

BrokenYugo wrote: I think the later 604s were improved somehow, my parents had one in a 4500lb AWD 1997 Grand Caravan that took a fair amount of abuse (towing 4000lbs, running on mostly dexron, blowing an aux cooler line at 70mph and losing a lot of oil) before it crapped out the lockup clutch at 180k, and then kept going with just a new converter.

I should specify I'm talking this gen a604 (1st gen?) Yes that later ones likely held together a lot better.

Chrysler made constant improvements to these throughout their run. So if you do rebuild it, make sure you research all of the improvements made along the way (including the TCU firmware updates) and incorporate them into your unit.

a version of it was also used in the Prowler, the 300M and the Cloud cars and there are ways to control it via the aftermarket, but probably not something you'd be concerned about for this rig.

It goes without saying, that unless you know the person who rebuilt it, I wouldn't buy a rebuilt A-604 from someone else. I know a builder here in the Portland Metro area that can build them so they never come back for warranty repairs. He also paints them all purple, so if anyone finds a purple one in a car in the junkyard, buy it.

Stefan wrote:

drainoil wrote:

BrokenYugo wrote: I think the later 604s were improved somehow, my parents had one in a 4500lb AWD 1997 Grand Caravan that took a fair amount of abuse (towing 4000lbs, running on mostly dexron, blowing an aux cooler line at 70mph and losing a lot of oil) before it crapped out the lockup clutch at 180k, and then kept going with just a new converter.

I should specify I'm talking this gen a604 (1st gen?) Yes that later ones likely held together a lot better.

It goes without saying, that unless you know the person who rebuilt it, I wouldn't buy a rebuilt A-604 from someone else. I know a builder here in the Portland Metro area that can build them so they never come back for warranty repairs. He also paints them all purple, so if anyone finds a purple one in a car in the junkyard, buy it.

For sure.

There were a lot of small changes in the first 4-5 years, but after that it was a pretty small trickle, and honestly nothing that was done at any point was a 'major' change in hard parts durability. My parents had a first-year (1989) 604 in a long-wheelbase caravan that made it to 180k before it started slipping. Other than drivability issues coming from programming in early models, the unit was never really that bad. Its reputation is out of proportion to reality.

But, the basic hard parts don't need beefing anyway. There was a neon that went 10s on an unopened 604. They put the same basic guts in a longitdunal case and put them in dakotas and smaller rams and liberties and nitros with 4000+lb curb weights and actual tow ratings. The only part that is weak enough to have a legitimate complaint about is.. wait for it..

The 4th gear clutch pack.

Update on the trans, and the van:

Since having the trans rebuilt (by someone I know) several months ago she's been driven daily with no issues. Dependable as the day is long. However a few days ago, I've lost out to a blown headgasket. Never having torn apart an engine that was built after 1978, I'm probably not going to have much success trying to repair this myself. Although I've been daily driving this van, I do have another vehicle for dd duty so having this one sit for awhile is not an issue. Maybe this is an opportunity to swap out to another mill? Having once owned a factory turbo Caravan, I can't say I'm opposed to having another turbo powered minivan. However having several hundred already spent on the rebuilt A604 auto, sticks in my mind. I would even be happy with a non turbo 2.5 at this point as I could always go turbo with it at some point. However I've never seen a 2.5 turbo or not, mated to the A604 trans.

Or do I go full off grid lemons mode and pull the almost rust free body and find a swb V8 Dakota frame to drop it onto?

Or do I pour in a bottle of Blue Devil and hope that solves the current headgasket issue?

I'd like to see a later Eclipse motor swapped in. No idea how many of the bolt holes would line up, but I've been curious as to whether it's a drop in for things with the earlier 3.0 SOHC and it would be interesting to see somebody try it.

MadScientistMatt wrote: I'd like to see a later Eclipse motor swapped in. No idea how many of the bolt holes would line up, but I've been curious as to whether it's a drop in for things with the earlier 3.0 SOHC and it would be interesting to see somebody try it.

I think already posted it was said that although it could be done, it may be cost and time prohibitive. One of the main issues is the non Mopar version had a completely different intake and exhaust manifold set-up which likely would not fit in the van without considerable work. I don't think the pure Mitsu motors would easily mate up with the Mopar trans and axles at least in my particular case? And likely need a pure Mitsu brain box to run it all.

If it were much simpler than this, that would likely be the route I'd go. Many of the pure Mitsu 6g72 SOHC motors made it a lot closer to the 200 factory hp rating than the Mopar knock-offs. Plus the factory turbo potential if you go the DOHC Stealth route.

All the 6g motors use the same bellhousing so technically any of them will bolt to that transmission. Of course there are other issues. The non-mivec sohc 3.0 and 3.5 as well as the dohc 3.0 have been swapped into old chrysler K-cars before. Nobody has done a 3.8 MIVEC that i know of, which is sad because it would be awesome!

Whatever money you spent on your trans would go to waste if you swapped to some other stock engine. None of the other engines that came in those vans will bolt to the transmission you've got. I would just fix the 3.0. It's not any kind of complicated by modern standards. If you want to make it fast, try to find an 'ed kelly' rear mount turbo manifold. It's the easy button. I have one and i am NOT selling it!

I have a good friend who daily drives a turbo 3.0 (same version as yours) dodge spirit with a stock longblock that has gone 113mph in the 1/4 mile. In the past he dyno'd 515whp on a built version of the same motor.

Vigo I think maybe I've seen the 3.0 Spirit your talking about on another site? Maybe TM? With having little to no experience with automotive computerization, even 1991 vintage, I have to admit this aspect alone is somewhat intimidating. As for upgrading the stock power levels of this motor, I know from reading on other sites the power limitations that the A604 faces without extra aftermarket (and maybe no longer available) help. So forced induction with this trans, although possible, may be out of reach financially at this point in my life.

Not sure if even comparable regarding trans strength or stock computer capabilities, but I do recall seeing "nitrous van" on the tube of you that I think had the same motor as mine, but not sure on which auto trans he had. He was throwing ever increasing amounts of nitrous at it but I don't recall seeing how the trans survived?