Where to get a front pump for a 42RH (A500)

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Map63Vette

Map63Vette

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So my brother's birthday is coming up and he has an old 94 Dakota V6 that was his first car and it's been showing its age pretty bad lately. I'm fairly sure the transmission is mostly junk, so I wanted to rebuild it for him as a present, but I'm having a bit of a hard time decoding all the different models and what parts will swap between them. The little V6 doesn't make any real power. so upgrading isn't really a concern, just a rebuild with lots of new parts. The truck is a 4x4 however, for what it's worth. I think the biggest problem with the unit is the front pump. I don't think it's making much pressure any more, so it's pretty sloppy on gear changes. The only pumps I've had any luck finding are on Ebay and are listed for a 42RE, the electronically controlled brother of the 42RH from what I can find. Are all the A500 series pumps the same and swapable between the different models, or do I need a pump specifically for a 42RH? Aside from that, any recommendations for a good rebuild kit and basic converter?
 
My guess is you most likely need a 42rh pump. Ma Mopar was famous for making changes every couple yrs. I have an A500 pump that I bought for a trans. I was rebuilding for a buddy and it didn't fit. If you can get me the casting # off yours I'll see if this one I have will work. It's in real good shape and you can have it for $40 shipped if it'll do you any good.
 
I'll have to see, it may be a bit before I get the chance to pull the trans. The truck still technically runs and gets used pretty often, so I'm not sure how long I can have it sidelined. On a different note, does the 4x4 have any bearing on the transmission? Didn't know if the tailshaft section was different to bolt up to the transfer case or not. I assume the internals would probably be similar, but figured it never hurts to try to double check everything before ordering.
 
Tail shaft does is different..but the rebuild kits are the same..
 
Map63Vette said:
I'll have to see, it may be a bit before I get the chance to pull the trans. The truck still technically runs and gets used pretty often, so I'm not sure how long I can have it sidelined. On a different note, does the 4x4 have any bearing on the transmission? Didn't know if the tailshaft section was different to bolt up to the transfer case or not. I assume the internals would probably be similar, but figured it never hurts to try to double check everything before ordering.
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No biggie. It's stored away in the parts containers. If you do find you need one send me a PM and we'll see if it'll work or not. Yeah the tail shaft section is different on a 4wd but I haven't been into one so I don't know how much different mechanically they are. I've seen them and it looks like it all unbolts easily.
 
The early pumps had a whine, so they increased the size of the take up ports in 1995. But the valve body port had to match the bigger pump port, so both the pump and the valve body changed.

There are also two different oil pump gear types, the older slotted drive, and the newer flat slot drive.

I think the 42RE uses the later pump with flat gear drive. So if you've got a later 42RH that has the bigger inlet port, you could probably use the 42RE pump, just get the correct gear for the type of torque converter drive you have (slotted or flat).

Here's some pictures of the different gears and gear drives, and a TSB that shows the difference between the two oil pumps:
 

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Cool, thanks for all the info, that should help a fair bit. I seem to have a knack for working on all the vehicles that have goofy one year only parts or mid year changes. My brother's other Dakota is a 2000 or 01, I can't remember, but his front axle stripped the splines and I got the pleasure of replacing both the stub shaft and outer CV axle because they changed the design mid year. Should be some fun detective work on this trans. Probably best to just pull it out first and double check instead of guessing. I think he could probably do without it for a while.
 
why would you think the pump is weak? did you put a pressure gauge on it?
 
I agree on checking pressure.I have built many a500 a518 transmissions and the pump is good 90% of the time.
 
How exactly do you check the pressure and what reading should I be looking for? What all fittings and tools might I need? I figured I would just try to T into the cooler lines, but I didn't know if that would be the same pressure that's in the transmission for the clutches and bands.
 
There is a 7/16 head plug facing to the rear of the transmission on the passenger side,that is the reverse test port. Install a oil pressure gauge and check pressure(make sure you use a gauge that goes to at least 300 psi). Car running in reverse it should have minimum 90 psi,then step in the gas(wot) and hold the brake to keep the car from moving and the pressure should go up to 175-200 psi,some times higher depending on a shift kit.
There is also a test port on passenger side in the middle of the transmission, which you can also test in drive.You will be checking the forward clutch pressure will be 50-120 psi.Wot will make the pressure rise.
The on test port in the front closest to the bell housing is the 2nd gear test port,no need to test for checking pump pressure.
 
Okay, thanks for all the info. I'll have to dig around and see if I have access to any gauges that will go that high. Pretty sure most of the stuff I have laying around maxes at 80 or so. Maybe I can get a loaner from the parts store or something. Nice to see there are easy ports to access though, should make it fairly straightforward to check.
 
If you don't have gauges and have a discount tool supply nearby you might check to see what they have. I have a discount tool house near me that gets a lot of buy outs. I've bought good liquid filled gauges that normally cost $80-100 for $20.

BTW: I attached a pic or the pressure test locations bronzebee spoke of. And just to note the main line pressure port in the middle of the case is affected by the throttle pressure lever position. If it's not properly adjusted the line pressure can appear low or high.
 

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Thanks for the pictures, that's exactly what I needed, lol. Been on the phone all morning trying to track down a gauge around here. Think I came up with something, taking a look at everything under the truck now. Would it hurt to just pull the kickdown line without revving the engine or will that hurt the pump or something inside?
 
I like to leave it hooked up to also check the throttle valve linkage adjustment.
A miss adjusted throttle valve will give you a low line rise reading.:thumbup:
 
I generally test it unhooked at first (and modulate it by hand) to see what the pressure is with the throttle pressure adjustment out of the equation. Then I hook it up and see what it is hooked up and if it needs adjustment then you can do it. Just my method but either way works.
 
Well, pressure does check out okay. The only gauge I could come up with only went to 200, so I didn't push the limits, but I hit around 160 with a little power braking, so I figured it was good.

The main reason I'm rebuilding the trans is because of some weird behavior that I'm trying to sort out. From my best guess I think the torque converter is randomly locking up when the truck is in gear (most noticeable at low speeds). For instance, as I was trying to pull it into the garage to start pulling things apart, every once in a while the truck would really tug at the brakes and the rpm would drop off enough to kill the engine sometimes (will sometimes even do it at stoplights). It's a 42RH trans, so it's hydraulically controlled, which I think should eliminate electronic issues from the equation. The torque converter was supposedly replaced back after we bought the truck around 10 years ago (converter was locked up when we bought the truck, took the trans to a shop). It does look fairly new now that I go the transmisison out (only put 40,000 miles or so on it since the rebuild), but I was considering replacing it. However, if the problem is in the trans and not the converter, I'd rather not drop the $100+ on a new converter. Any ideas where the to look for the problem? I bought a rebuild kit anyway because I think the clutches are probably pretty worn out, but I don't want to get the whole thing back together and find out nothing changed, especially since I spend 8 hours under the truck yesterday just trying to get the damn thing out.
 
I don't know much about lock-up transmissions but quite a while back I remember reading some information somewhere on them that talks about the problem your describing. I'll do some digging and see what I can come up with and post what I find later this eve.
 
Thanks! I appreciate any help I can get. It seems like there would have to be some signal to trigger the lockup, but there's only two plugs on the trans, one for the reverse lights / neutral/park safety, and one other two pin one. I was thinking it was the speedo at first since there isn't one anywere else, but I don't know that it is since it points down into the pan. I'd heard it was maybe the overdrive control, but I was going check the manual for the truck when I get home for a wiring diagram. There are two plugs in the transfer case as well, so the speedo might be in there to account for low gear I suppose.
 
Recheck the connector that faces up behind the shift linkage.If it is a 2 pin connector then the transmission has no lock up just overdrive.
If the connector is yellow it's a 2 pin.
If it has 3 pins then it has lock up and overdrive.
I can't say for sure,but i don't think they made a 42rh with no lock up function.
 
It is a lockup, I got it all apart yesterday and can see the lockup solenoid in the trans. Found out the accumulator spring was broken, so I need to try to find one of those somewhere. Otherwise it didn't look too bad inside. There was a little metal in the pan, but the fluid wasn't all the dark and the clutches were decent, though one set looked pretty dark. Not sure if the accumulator spring would cause the issues I'm running into or not. May try to open up the valve body and see if there is a bunch of junk in there or something that may be clogging a port.
 
How many solenoids are in the transmission one or two?You don't need the accumulator spring.
 
BB is right, the accumulator spring isn't a necessity. All it does is cushion the 1-2 shift. Nothing to do with the lockup. Sorry I never got back to you yesterday. I'm diabetic and got real sick. Just finally getting around again. I found that information and it actually can be an electrical problem. The computer sends a signal to the lockup relay which in turns activates the lockup solenoid that directs oil to the lockup function of the converter so any malfunction of that circuit such as a sticking solenoid or relay or computer issue can cause your problem. It also mentions it can be a problem in the VB such as a sticking switch valve, lockup valve, or fail safe valve. Since you already have it apart your best bet is to completely disassemble the VB and thoroughly clean it and check for worn/sticky valves. I don't know if there's a way to check for computer codes with it disassembled or not.

As mentioned the broken accumulator spring should have no effect on your problem but without it it may shift kinda stiff going into 2nd. If you need one PM me the dimensions. Most likely I have one that's real close and you can have it for shipping which will be about $5.

BTW: BronzeBee your correct that they didn't make a non lockup A500/42rh
 
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