'97 chev van code p1870

billr

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#1
It has about 80K miles on it, and has the VIN "R" 5.7 V8. There is a cat-converter heat-shield covering the trans data-plate, but I think it is a 4L60-E. There is a modulator-type can on the passenger side of the trans case and the case has "24202519" cast-in on the driver's side. Recently we have occasionally noticed a hard 1-2 shift after everything was all warmed up. Now, the P1870 was set and the SES light came on. I erased the code and it hasn't come on again, even after a couple of 40 mile highway drives today. I understand that P1870 indicates trans slippage and is probably caused by a valve spool riding in a worn housing. Most likely to occur when trans is hot and then the computer sets hydraulic pressure up to max in attempt to prevent continued slippage; hence the hard shift. Symptoms all pretty consistent with what I have going on. I pulled off the torque-converter dust-shield, the converter doesn't look at all discolored from over-heating. I am tempted to pull off the pan and inspect for abnormal debris, then change the filter and fluid (I think both are original). Unfortunately, we are scheduled to take this van from CA to PA (and back) in a couple of weeks (no towing); what are the odds that the trans will last OK? Will synthetic fluid help the situation? If I buy a new or rebuilt valve body can it be "reasonablly" replaced with the trans in the vehicle; should I consider doing that while I have the pan off?
 

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#2
Don't buy a VB yet and we need to identify this trans, the only trans to use a modulator that is still used in '97 was the 400 series trans but this one is non computer controlled nor should you get a slippage code unless somebody has converted out the 4L60E and put a 400 in it's place. If they have done this then you should be getting a bunch of codes. Can you describe this transmission's pan? Shape & bolt count will help. Is there a spin on filter on the bell housing area? Is there a big electrical connector into the case on the pass side just above the pan ledge? Post back and we can help more, Transman
P.s. Post with more info on the van itself too, exactly what series van is it? Any add ons? (air filter, remote start..etc) Have you checked the fluid level? Is it full? Color? Odor?
 

billr

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#3
Transman,

It's a 1500-series (1/2 ton) Express van; absolutely stock, we bought it new. Fluid level is OK, looks OK (for 80K miles) and no unusual smell. No spin-on filter, I think. I don't recall there being any electric connectors on the passenger side (other than speedo), but there is a plastic housing between the shift lever and trans case that has two connectors. The pan is relatively rectangular, 16 screws (5 left and right, 3 front and rear). I can take off the cat heat-shield and get to the trans data-plate tomorrow. Will look more carefully for connectors & spin-on, also.
 

billr

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#4
more info on trans model

I found the original dealer-delivery info. The trans is listed as an "M30" 4 Speed Electronic Automatic Transmission With Overdrive.
 

billr

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#5
confirmed it's a 4L60-E?

The ID on it is 7CHD035H, there is an electric connector on the passenger side (round, plugs in straight down), the cooler lines are just behind the bellhousing and angled forward. Still can't see anything that looks like a spin-on filter (except for on engine, of course). That thing I thought looked sort of like a modulator is actually a big bore cast in the trans case and closed off with a steel cap held in place with a round-wire internal snap ring. It is below the cooler lines and forward of the electric connector.
 

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#6
Okay, this makes more sense, the "can" you are talking about is the 2-4 servo and the trans is a 4L60E. Without a "pan drop" it will be hard to determine the shape of this trans. The common practice with this code is replace the VB, however this is not the cause and eventually will wear out again. The cause is the pump stator bushing actually which blows off more oil than the passages can replace causing the pressure regulator and lockup valves to wear out the bore in later stages (hence the VB replacement). I have found that if the trans is basically in good shape that a bottle of Lubegard helps by restoring the friction modifiers and helping the torque converter clutch "bite" better. A service with filter would give more info on the condition of this tranny. Also, remember that any other problems in the engine can cause this code too, I don't know why but it does. I have seen bad TPS, MAF and EGR all cause this code. Check all connections and grounds for problems and corrosion especially at the battery. The Range Mode Switch (Neutral Switch) is another problem on these units. Even getting the connector off can be a major operation as the sealer inside tends to turn into krazy glue and you end up breaking the connector or switch just getting it apart. They sell new connectors at the dealership for this very reason. Good Luck and post back, Transman
 

billr

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#7
Sorry about that misleading "modulator" info, I couldn't see it very well until I had the cat heat-shield out of the way. I will pull the pan off tomorrow and look for debris. The van drives flawlessly, except for the temporary hard 1-2 shift when slippage is detected, so I don't expect to find any of the sensors bad; but I will check what I can. Especially, I will check the battery-engine-chassis grounds and will make sure all connectors to the trans are fully seated. When I refill the trans should I use synthetic (do they even make that)? How many quarts should it take, considering that I probably won't be draining the converter, right?
 

billr

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#8
OK, I pulled the pan and filter. Wow! That valve body sure has a lot of widgets and gadgets on it. The fluid is more brown than red now, but still fairly clear. The pan had only a light layer of "dust" in it, no particles or chunks. The magnet has a coating of "fur" on it, but no particles or chunks there either. There is no burned smell, and the top of the filter was pretty clean. So... my present plan is to put in a new filter, put the pan back on, and replace the fluid drained (about 1 gal) with full-synthetic; then hope for the best!
 

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#9
When you say full synthetic... What kind is it? You should be using DEX VI now unless someone still has DEX III left in stock. Do NOT use Multipurpose fluid in this tranny. You will know this by reading the label, if it says it meets DEX III/Mercon, ATF+3,ATF+4 (chrysler), Honda, etc. The only acceptable fluid for this trans is old DEX III or the new DEX VI. Chuck a bottle of lubegard "Red" and your slip code should go away.
The material inside the pan is normal for GM units. You need to smell funky and have Pieces of metal inside to be concerned. Post back, Transman
 

billr

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#10
The fluid I have to put in is DEX VI, and I'll get some Lubegard. Assuming all goes well after the pan is re-installed, I won't post again until after my long trip; I'll let you know if the trans survived! Thanks for your help.