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  #16  
Old 05-29-2002, 09:16 PM
InukSean
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Quote:
Originally posted by vkykam
I hope I'm not too late jumping into the thread here. I've, um, neglected the board for the past 6 weeks. Yes, yes, shame on me.

Anyhoo, don't overlook the obvious. What are the condition of the tires? Do the tread depths match from front to rear? If I recall correctly, all it takes is 2/10ths of an inch difference between front and rear tread depths to cause binding as well.

Good luck.

VK
I'm pretty sure that the treads on all tires are evenly worn.

Add to that the fact that the plugging in of the FWD fuse completely eliminates the problem and the transfer pressure reading abnormally high, I doubt that this could be the LONE cause.

I will,however, take the time to check it out.


Thanks for the suggestion.
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  #17  
Old 05-29-2002, 09:30 PM
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vkykam vkykam is offline
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I couldn't explain the high transfer pressure, but if the FWD fuse is in, and the binding goes away, it can point to the tires.

If, say, the tires weren't rotated at proper intervals, and the fronts wear down faster than the rear due to the weight, you could potentially have the fronts 1/4" less in diameter (not tread depth) than the rear. This would cause the TCU to think that there's slippage, as every turn the rear wheel takes, the fronts would take just over one turn, enough to throw off the TCU.

It may or may not be the cause of the problem, but at least it can give you hope of a cheaper solution.

VK
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  #18  
Old 05-29-2002, 09:33 PM
InukSean
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Quote:
Originally posted by vkykam
I couldn't explain the high transfer pressure, but if the FWD fuse is in, and the binding goes away, it can point to the tires.

If, say, the tires weren't rotated at proper intervals, and the fronts wear down faster than the rear due to the weight, you could potentially have the fronts 1/4" less in diameter (not tread depth) than the rear. This would cause the TCU to think that there's slippage, as every turn the rear wheel takes, the fronts would take just over one turn, enough to throw off the TCU.

It may or may not be the cause of the problem, but at least it can give you hope of a cheaper solution.

VK
I will DEFINITELY check it out.

Diamater, eh? Gonna be tough to notice a slight difference.
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  #19  
Old 05-30-2002, 07:33 AM
kuoh kuoh is offline
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Stick a small piece of chalk in the tread at the top of each tire, preferrably a different color for each tire. Then drive straight for at least one tire rotation and measure the distance between corresponding chalk marks.

KuoH
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  #20  
Old 05-30-2002, 07:56 AM
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<<the plugging in of the FWD fuse completely eliminates the problem and the transfer pressure reading abnormally high>>

I can't beleive no one has mentioned a clogged cooler/filter. Sorry I wasn't following along on this thread earlier.

try bypassing the external filter and radiator cooler by taking a peice of hose and connecting the inlet metal pipe to the outlet metal pipe on the frame rail under the battery.

Drive around for only a few minutes as you have no cooling of the tranny at this point. If the binding is not present, then you have found your problem and need to replace the filter and backflush the stock cooler. A second pressure test would probably confirm this giving normal readings.

Replacing the filter and installing an aftermarket cooler has completely ended the binding that I had for over 5 years. It has been bind free for almost a year.

Doug
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  #21  
Old 05-30-2002, 01:20 PM
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Good point there! Even after my transfer case blew and got rebuilt, I hadn't noticed that the filter was installed with reverse flow. In retrospect, all the times I'd complained about tranny fluid leakage and the subsequent tightening and retightening of the hose clamps (indicated on the service tickets) should've given somebody there a clue. It wasn't until I decided to install an external cooler and temp gauge and decided to replace the filter as well, that I noticed the flow problem.

I think this would be the perfect time to install a temp gauge, if not an external cooler and replace the filter as well.

KuoH
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  #22  
Old 05-30-2002, 07:00 PM
InukSean
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There is already an external cooler. It was installed in March.
The problem pre-dates the addition, but I can't be 100% sure about the filter part. i guess I should get it checked.
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  #23  
Old 05-30-2002, 08:02 PM
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Earthworm Earthworm is offline
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Question about the external tranny filter:

Should the fluid coming from the tranny flow through the filter or the radiator first?

Mine is/was set up to flow through the radiator cooler then the filter then back to the tranny. I would have thought that it would be best to flow through the filter first to prevent further clogging in the radiator cooler.
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  #24  
Old 05-31-2002, 04:39 AM
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Quote:
I can't beleive no one has mentioned a clogged cooler/filter. Sorry I wasn't following along on this thread earlier.
This doesn't make sense to me. A clog anywhere in the tranny or filter should not increase the transfer pressure. The transfer valve has two spool valves. The first one is a pressure regulator and it regulates the pressure to the 2nd spool valve, the transfer valve. The transfer valve applies the pressure to the transfer clutch plates.

The regulator valve is required because without it the transfer presure would be going up and down as the line pressure changed. Another way to look at it; pull the line pressure resistor and the line pressure increases. The transfer pressure does not increase.
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  #25  
Old 05-31-2002, 04:49 AM
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Good info a little late.

I measured the transfer pressure and the line pressure on Sean's car. Basically the transfer pressure is running around 46 psi at idle with the car going no where. The spec for this is about 10 psi. A light touch on the throttle to about 2000 rpm with a foot on the brake and the pressure goes up as it should.

Removing the line pressure resistor had no effect on the transfer pressure and that appears okay.

The line pressure at idle with the resistor plugged in was normal and with the resistor unplugged went up as it should. So this appears to working just fine.

It would appear that the transfer valve assembly is worn out. However, after RJ's problem with the TCU I am not sure because the "power light" on Sean's car did not come on with the resistor unplugged after starting the car twice. Sean's is going to check this out again. This seems unusual and maybe similar to RJ's no FWD light coming on.

The tranny diagnostic says no prior codes.
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  #26  
Old 05-31-2002, 07:20 PM
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<<This doesn't make sense to me. A clog anywhere in the tranny or filter should not increase the transfer pressure>>

I'm not that veresed on the innerds of the tranny, but My best guess and backed up by a few better knowledged than me, is that if the pressure on the cooler line is too high, then the duty solenoid "C" can't hold back the pressure and some leaks through and energizes the rear causing the binding.

I don't claim to be an expert, all I know is it worked for me and I figured I'd pass on the low cost possibilites.

Doug
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  #27  
Old 06-01-2002, 11:25 AM
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The pressure to the cooler is regulated. There is a relief valve built into the control valve body. It has to be there If the line pressure, which can reach 210 psi ever got thru to the cooler it blow it apart. The pressure to the cooler can also be measured. It doesn't increase when the line pressure transistor is removed.

A flush is always a good idea and can't hurt anything.

John
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  #28  
Old 06-01-2002, 06:34 PM
oab_au oab_au is offline
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Re: Good info a little late.

Quote:
Originally posted by svx_commuter
I measured the transfer pressure and the line pressure on Sean's car. Basically the transfer pressure is running around 46 psi at idle with the car going no where. The spec for this is about 10 psi. A light touch on the throttle to about 2000 rpm with a foot on the brake and the pressure goes up as it should.

Removing the line pressure resistor had no effect on the transfer pressure and that appears okay.

The line pressure at idle with the resistor plugged in was normal and with the resistor unplugged went up as it should. So this appears to working just fine.

It would appear that the transfer valve assembly is worn out. However, after RJ's problem with the TCU I am not sure because the "power light" on Sean's car did not come on with the resistor unplugged after starting the car twice. Sean's is going to check this out again. This seems unusual and maybe similar to RJ's no FWD light coming on.

The tranny diagnostic says no prior codes.
Thinking about the way.the fuse disengaged the clutch. There is a difference in the signal for the FWD fuse and the modulated signal. The normal signal sent to the C solenoid is a 'mark space ratio ' where the voltage is turned on for a portion of the cycle and off for the reset of the cycle. The ratio of on time to the off time controls the clutch pressure. The FWD signal is straight DC. It would seem to me that the magnetic field would be much stronger with the DC signal than the modulated one. May be that is why the fuse works the C solenoid but the lower voltage signal won't. The solenoid may be failing mechanically??

Will be getting my workshop manual any day now. All will be revealed
Keep up the good work mate, your worth more money(see Randy)
Harvey.
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