Transmission problems?

Take a step back for a moment and lets straighten out some misconceptions. Transmission cooler hoses blow all the time. That is not a reason to replace the entire transmission. The loss of fluid will eventually cause air to get sucked up by the pump. That air can be compressed and will prevent the clutch packs from engaging. The slippage at first will cause excessive wear, but will be very noticeable. If it is able to continue long enough, it will take miles for internal damage to occur.

The next issue is the valve assembly. That is a series of electrically-operated valves that control fluid flow to the various clutch packs. Changing that isn't going to solve anything.

Another concern is the wrong fluid. We run into that all the time on all different brands of vehicles. The symptom is the wrong fluid formulation causes the clutches to engage too harshly. There needs to be a little slippage as engagement occurs, to make for a smooth. Comfortable shift, not one like in a race car. At around 45 mph, give or take, an internal clutch in the torque converter will gradually start to engage. This is a Chrysler innovation from the mid '70s for improved fuel mileage. When the wrong fluid is used, the clutch will engage too harshly, engine torque will break it free, then it will try to grab again. You feel that as a shudder during that period of engagement, and that can be just annoying all the way to pretty harsh. One of my Caravans did that for years. To stop that shudder or to prove that is what is happening, simply hold road speed and the accelerator pedal perfectly steady, at around 40 - 45 mph, then when the shudder occurs, lightly tap the brake pedal with your left foot. That signals the torque converter clutch to disengage. Once the computer sees you are not planning on coming to a stop, the clutch will re-engage in about three seconds. The wrong fluid doesn't do other damage to the transmission. In some cases you can have an additive in one brand of fluid that isn't compatible with the additives in a different brand, but that doesn't lead to a major breakdown. This applies much more to engine oil. For example, when you change from one brand to another, the new oil might have a detergent that will attack the seal conditioner in the old oil. There's also dispersants that carry sludge to the filter, anti-corrosion agents, and viscosity index improvers that may not be compatible, but at worst, they lead to oil leaks, not breakdowns.

P0734 - Gear 4 Incorrect ratio
P0735 - Gear 5 Incorrect ratio

These fault codes set when there's slippage in a clutch pack. I'm questioning code P0735. There's only four clutch packs in your transmission, and in various combinations, they create four forward gears. There's a signal from an "input speed sensor" and one from an "output speed sensor". The Transmission Computer knows that for a given engine speed, the road speed must be a certain value, based on the gear the transmission is currently in. When slippage occurs in a clutch pack, engine speed goes too high for the current road speed. That's how it tells there's slippage and which clutch it's occurring in. Those codes are going to set if the slippage was from the loss of fluid. All that is needed is to erase the codes. That is done with a scanner, or, for your model, simply removing a battery cable for a minute.

This computer-controlled transmission is another of Chrysler's innovations that others use their own version of now. One of the things they included is the ability to read the "clutch volume index", (CVI) on a scanner. That's a set of four numbers representing the volume, in ccs, of fluid it takes to apply each clutch pack. As the fiber plates wear down, it takes more and more fluid to fill the drum before the plates are fully squeezed together and lock up. A transmission specialist can tell by those numbers how much life is left in each clutch pack. As I recall from training a long time ago, one of the common maximum values was 80 ccs, but don't hold me to that. The specialists should know, or it can be found in the service manual. If one of those numbers is nearing its maximum, that would be reason to install a rebuilt transmission.

Another part of this design is the computer constantly updates its shift schedules in response to that clutch wear. There's advantages and disadvantages to that. The good part is years ago with regular hydraulically-controlled transmissions, we had a good two or three years of warning that a rebuild was in our future, based on sloppy upshifts and engine runaway during those shifts. This was worse at very low speed, gentle up-shifts. On your transmission, the computer sees that clutch plate wear and updates, or learns, how to make the shifts so they stay as crisp and solid as the day it was new. For example, it will apply third gear, then wait just a little longer before it releases second gear. That way, by the time second gear lets go, third gear has had time to lock up. You feel the solid shifts, all the way up to the day the computer can't update any further. That's when the slippage occurs and is detected, and the computer puts it into limp mode where it stays in second gear. That's to allow you to drive slowly to the repair shop without needing a tow truck. The disadvantage is you never got that sense of wear taking place. One day it shifts fine. The next day it goes to limp mode. ==

One way to work around that, often for months, is just as it's getting ready to up-shift into the next gear when the slippage occurs, accelerate a little harder than normal to get past that speed, then let off the accelerator pedal until the up-shift completes. Once the clutch has locked up, it can stay that with no slippage until a lot more wear takes place.

I have to apologize. I see the error of my ways. I copied the wrong fault code. Should have posted:

P0733 - Gear 3 Incorrect ratio
P0734 - Gear 4 Incorrect ratio

The four clutches are the front clutch, rear clutch, under-drive clutch, and the over-drive clutch. Multiple clutches are engaged for each gear, so those CVI numbers are needed to know which clutch is slipping.

This is why I said to step back for a minute and think this through. The original proper repair should have been to replace the blown cooler hose, refill the fluid, then optionally, wash off the sprayed fluid to clean the area up. The Transmission Computer does not sustain damage from things like this, so it never should have been replaced. Same with the valve assembly. You won't destroy the clutch packs in a mile and a half unless one of them was very near to the end of its life already. If that was the case, this hose was just the last straw on the camel's back, so to speak.

If I've followed this correctly, you now have a different transmission with different amounts of clutch wear, and you have a different computer that has stored learned values from yet some other transmission. Two variables that require the new computer to learn the CVI numbers for the current transmission. That relearn can take up to two miles and up to a dozen up-shift sequences. Until that relearn is finished, the transmission can shift too harshly, like a race car, or too sluggishly, resulting in slippage, fault codes, and going to limp mode. In about 90 percent of cases, shifting is fine and normal after only one item is replaced. We always take your vehicle on a test drive to let the relearn take place before you get the car back, but again, most of the time we don't notice anything unusual.

I have to correct one thing I just said. When the computer is replaced, obviously it is unplugged from power until you plug it in. That being without memory 12 volts causes it to erase any fault code from the vehicle it came from, and it reverts the learned values to the factory default values. In other words, it's the same as installing a brand new computer that has never been in another car. They start to learn the new CVI values as soon as you start driving.

Dandy observations. I did think of something that might be in the back of your employee's mind. A lot of computer modules now have different memory characteristics. We can program speed-sensitive door locks, and other personalized settings that require a scanner, but those settings aren't lost when the battery is disconnected. As far back as on '94 Dakotas, you needed a scanner to erase diagnostic fault codes in the ABS Computer. Disconnecting the battery wouldn't do it.

I ran into this with tvs too in the late '90s. RCA, which has always had messed up designs, put almost 150 adjustments in one EEPROM. Those had really horrible problems, but when you unplugged them, even for months or years, those settings were retained

Other than those oddities, disconnecting a battery cable was the common way to erase fault codes. Doing it that way also erased all the learned data for fuel trim numbers, but those tables were rebuilt as soon as you started driving again, without you even noticing. Sensor personalities are relearned too. No two are ever exactly alike.

Regardless, as long as you have a scanner, you're all set. It's much faster and easier to erase codes that way. I understand your thinking with the transmission and module.

You're in an area now not of my expertise. You should be able to get a definitive answer from the guys at a Chrysler dealership's parts department.

Here's what I can share with you. The 3.3L and 3.8L engines share the same block, bolt patterns, and mounting points. Transmissions from either engine and from multiple years, will bolt up to those engines whether they're in a car or minivan. The bolt holes are the same on all those transmissions for the driver's side mount. If there's differences between cars and vans, it will show up in the metal bracket that bolts to the transmission and to the body.

I think the solenoid pack (valve assembly), is the same, so the electrical connector will be the same. To double-check that, I'd suggest looking on Rock Auto to see if the part numbers are the same for the various applications.

The biggest thing I might question would be the gear ratios, including the "final drive". That would equate to the gear ratio of the rear differential on a rear-wheel-drive vehicle. While those won't prevent one transmission from working in a different vehicle, they might be different for different vehicle weights. If there is such a thing as different gear ratios for all four gears, I have never seen where those need to be entered through a scanner. The final drive ratio and tire size do have a place to enter them so the speedometer will read correctly. That information is stored in the Transmission Computer, and is retained indefinitely when the battery is disconnected.

We also need to look at the number of splines on the inner CV joints where they slide into the transmission. Chrysler has always been very good about parts interchangeability, and with the splines, I have never run into a shaft with the wrong number of splines. While half shaft lengths can be different for different models, I've never had a joint that didn't slide into the transmission.

I just looked on Rock Auto and found they don't have listings for the complete transmission, but I did find the solenoid pack is the same for your '98 van and my '93 Dynasty. They don't offer just the inner CV joint housings so I couldn't compare those. The half shaft part numbers are different, typically because the lengths will be different. In fact, like normal, your right shaft is a lot longer. My Dynasty uses an intermediate drive shaft on the right, so the two front half shafts are the same length, and interchangeable.

One more thing to look at that I hadn't considered is this transmission was called the A-604 when it came out in 1989. Chrysler's was the world's first computer-controlled transmission. Today it would be called something like a 42TE. The "4" is for four speed. "T" is for transverse, usually used in front-wheel-drive models. "E" is electronically-controlled. The "2" refers to how beefy it is, or how much horsepower or torque it can handle. That second digit can be higher on the replacement transmission, meaning it's stronger than the one you removed, but you don't want to go lower than what came in the van originally. A lower number would still function, but it would be more suited for a four-cylinder engine.

(Can't wait for the salt to get off the roads. I'm going to start driving my Dynasty this summer. In another 50 miles, it will have 5,000 miles and be ready for its second oil change).

Part numbers can be confusing. Often you're better off just going by the application, not the numbers.

With the car radios I work on, a P4704383AD, for example, has had three minor revisions since the original P4704383AA came out. The last two letters mean there has been some revision, but it's too insignificant to warrant a different part number.

When there's a bigger change, it gets a new part number, but it might interchange perfectly with multiple other numbers. In one case, when an emissions problem is corrected by "reflashing" the Engine Computer with updated software, if it involved a recall, we have to place a new part number sticker over the old one. Instead, if the computer had a problem before the recall went into effect, and it went back to a repair center, it gets repaired first, then any updates are performed, then the latest software gets installed. That module will get a still different part number so the rebuilders know the module's history if they get it back again. There can be a dozen different part numbers, all for identical computers that will all work in that same application.

Your rebuilt transmission is going to have a different part number too. By '98, most of the mechanical updates were incorporated already, but for older models, those that go back to Chrysler to be rebuilt will get updated clutch drums with relocated sealing rings, and the clutch packs will be stuffed with as many clutch plates as they can fit in there to give it the higher rating to a "42TE", for example. The cost of those additional clutch plates is almost nothing, but now that transmission can be used in more applications.

I've also been told a rebuilt assembly can get different part numbers to denote which supplier or rebuilder did the job, but I don't know that for a fact.

You can even find the part number on the transmission is different from the number on the container it was shipped in, or the number on the invoice. Three transmissions with the same number could come as different packages, with different numbers on the boxes. One might come with an updated rubber mount. One might come with a set of special bolts. Yet another one might have been shipped without the solenoid pack, but they all work in the same applications.

When you consider there's thousands of parts for every model and year, and many of them are subject to changes or improvements, it's not practical to denote those changes other than to put a new number on it. Even with my radios, there can be from two to a dozen different model numbers covered in one service manual, but all the internal parts interchange.

As far as I can remember, the cases are the same for both versions, and they mount the same. The only difference is the AWD model has an extra flange for the rear driveshaft that you just wouldn't connect anything to. That can be allowed to freewheel, as long as it won't rub on a cross member. I do know people have gone the other way by taking off the rear driveshaft, then installing the 2wd transmission in place of the AWD. That was on a '93 model which was the previous version of Caravans. You'd have to compare the cross members, firewalls, and check if power steering hoses would be in the way.