Mopar minivan trans question

His username is Ondonti on Turbo-Mopar.com and Turbododge.com.

One thing to keep in mind: Transmissions don't care about power, they care about torque. Without nitrous or boost nothing you can do is going to give the trans any problems. Keep in mind that as i said earlier they put the SAME guts in RWD transmissions cases and installed them in trucks with 3.5-4.0L engines in vehicles with max GCVWs of probably 8000+ lbs. You can afford to make a little more torque before the transmission will really care.

It's already been proven that the stock clutches at stock pressure will hold a lot of torque. The problem with the 604 comes when you try to apply all that torque during shifts and the accelerated wear that happens during those shifts ends up killing the trans early. There are ways to kill torque during shifts and compared to installing a supercharger or turbocharger they probably aren't even AS complicated as making the torque in the first place.

Since i said that i just thought up a little system where you run a 2-step boost control off an rpm window switch so that you kill some boost right before WOT upshift rpm, and then use a pressure switch and a diode to short the TPS signal to the TCM to 5v so that the TCM thinks you're WOT any time you're over X psi of boost, and you don't get an upshift until you let off. So.. you either part throttle boost and don't shift until you let off enough to kill the boost (like a manual! lol) or you WOT all the way up to redline and the wastegate goes to minimum boost 100-200 rpm before the upshift. I dunno, doesn't seem impossible to me. If you go with a piggyback or standalone or even a recalibrated stock computer you could probably accomplish everything inside the engine management by just pulling timing. Stock chrysler minivans (and a bunch of other 604 cars) did that exact thing from the factory starting in 1994.

"I just thought up a little system"!! That's amazing for sure. I will read up over there on his 3.0 set-up. Maintaining dd reliability will be key but based on what your saying it sounds like that can be done.

Random question that is still related to the main point of the thread, kinda.

Since my ideal minivan for anything I want to use one for has lots of low end grunt instead of high end anything, how do the 3.0/3.3 motors take to superchargers?

The awd setups they used on them too, since the trans can possibly handle the amounts of massive leaky boost a junkyard supercharger would put out.

Can't you control the 604 with a modified MegaSquirt?

That might be a way to get around the factory computer stuff and allow a standalone for the engine to add power or perform an engine swap.

Since my ideal minivan for anything I want to use one for has lots of low end grunt instead of high end anything, how do the 3.0/3.3 motors take to superchargers?

3.0 and 3.3 are totally unrelated engines. The 3.0 has been supercharged many times, the 3.3 not so much. The 3.3 (and bigger 3.8 version) have been mostly ignored by enthusiasts because they never came in anything but minivans and grandma cars with automatic transmissions whereas most of the 3.0 stuff was figured out on the Daytonas and Shadows you could get with manual transmissions that would run in the 15s (14s in very specific cases) bone stock. People just transferred that knowledge to van application. The 3.3/3.8 compare favorably in headflow and general reliability, but they're massively undercammed and megasquirt didn't become a reality until most people had given up caring about the idea of modding one. They have been run on megasquirt, but as far as i know noone has actually done a build that did megasquirt justice (big tb/plenum/cam/rpm or boost).

The 3.0 is easier to supercharge because the top of the plenum is totally flat except for ribs that can be milled off, so you can literally bolt an m90 to the top of it dumping directly into the stock intake manifold.

The awd setups they used on them too, since the trans can possibly handle the amounts of massive leaky boost a junkyard supercharger would put out.

Somebody once built an AWD 3.0/5spd grand caravan and then didn't follow through by making enough power to justify it. But, he did drag race it and it survived every 3600+lb dragstrip launch behind a manual trans. Automatics are a cake-walk compared to manuals when it comes to breaking driveline stuff. The actual pto/tcase is super beefy compared to what's found in most fwd-based awd cars and pretty much all the failures in stock vans had to do with letting all the fluid leak out.

Can't you control the 604 with a modified MegaSquirt?

Yes, it's been done. The problem is that the MS doesn't measure and adapt to the clutch-fill times like the stock TCMs do, so it will work but you'll either be retuning it regularly to compensate for wear, or the tune will 'drift' over time. It's good enough for a drag car. Not a great option for a DD.

In reply to Vigo:

Only reason I say 3.0/3.3 is because the years I'm looking for those two were the most common engines. I don't think I've ever seen a 3.8 square bodied van.

The 3.3 could be had in a 1g van for 1 year only, 1990. No 3.8 in the 1g.

The 1991-1995 vans could get both 3.3 and 3.8, depending on options/trim etc. I'm not totally sure that you could get a short wheelbase 3.8 in that generation, though.

How many hours approximately does a HEADGASKET job take on this 3.0? Going in this far it's a good time to look around and take care of any other issues in there at this time.

Labor guide says about 8 hrs, but labor guide assumes proficient technician with all necessary tools. I'm not saying that to scare you but it's VERY hard to predict how long something will take a specific person i don't know with tools i don't know in a workspace i dont know yadda yadda.

Timing belt and water pump are obvious but one thing you should probably do while the heads are off is take out the water pipe that runs down the valley of the engine, check for impending rust-through and replace the big o-ring at the water pump end.

Also there is a way to trim the ac compressor bracket to make the next timing belt r&r much easier but i forget the specifics.