4WD Problem

[blockhead]

4WD PROBLEM
2000 LTD with multimode and e-locker.
4WD (AWD) will not engage with MM switch and indicator light flashes.
4WD H4L will not engage with transfer case lever and indicator light flashes.
I am able to get it into L4 but I do not believe the front differential engages (with some circa 1970's gear grinding before they mesh before it goes into a Low 2 wheel drive).

Vacuum Switching Valve (Solenoid Assy., 4WD Control) #85440-35040
A.D.D. Indicator Switch is good
4WD Position Switch 1 on transfer case actuator is good.
4WD Position Switch 2 on transfer case actuator is good.

Transfer Case to Actuator (#3641035051(40))Tube #044105001 replaced with no change.

Actuator Assembly, Differential Vacuum (A.D.D.) #4140035020.

Red has constant vacuum of over 15 in.Hg
Blue has no vacuum regardless of 4WD switching

A.D.D. Will not actuate with vacuum of up to 20 in. Hg applied to either side.

I still have to test the VSV solenoids with 12 volt jumper and ohmmeter, and am hoping they are good.

I suspect the ADD may have failed. Can it be removed and repaired or only replaced?

Any suggestions or advice would be greatly appreciated!

 

[TheDurk]

Well, you clearly have more than one problem, if the info is accurate.

1. Vacuum does not switch sides when you engage 4wd.
2. When you reverse vacuum manually, the ADD does not engage.

As to 1, The next thing is to use that ohmeter on its volt setting to see if the 12V+ signal to the VSV's switches sides when you engage 4wd. If it does, then you have an issue with the VSV's. If it does not, you have a problem upstream in the 4wd ECU or its inputs (power, ground, the button itself, detection switches, or in the 4wd ECU itself.) So that test is key.

As to 2, you need to pull the vacuum actuator on the front diff and see if you can free up the mechanism. Or, if it works off the diff, then you have a problem in the diff itself.

Can you confirm that the T/C locks the front propeller shaft when you engage 4wd? It should rotate by hand in 2wd, then lock up at both the T/C and the ADD when 4wd engages.

 

[blockhead]

Thanks, I'll pull the ADD tomorrow. What's the best tool to access the 3 switches on top of the transfer case, they seem to be a booger to get to.

I cannot confirm shifting of the TC at all except manually into low as above...

 

[Quadsbc]

Similar issue but a lot of info here

http://www.toyota-4runner.org/3rd-gen-t4rs/180002-odd-4wd-issue-searched-still-need-help.html

 

[Quadsbc]

This one too

4WD won't disengage on 99 4Runner LTD - YotaTech Forums

 

[blockhead]

Thanks, [MENTION=10169]TheDurk[/MENTION]. I did get it into 4WD with a 12v10a jumper wire on what I thought was the 2/3 poles on the connector, but as it looks different than the connector shown in the FSM I have, I think it was the 1/2. Had trouble getting it back out, but it finally did after operating the 2-4 switch and transfer lever repeatedly.

The front driveshaft (TR-DIFF) turns freely.

I'd like to check the switches on the top of the transfer case to confirm they are not part of the problem, but they are challenging to get to, to say the least. Any advice there?

 

[blockhead]

Ok, here's more. As suggested in another thread (thanks again [MENTION=10169]TheDurk[/MENTION]), I turned off the engine, but left full power on and operated the TR case lever from H2-H4L multiple times. I heard a quiet "click" by my left foot, and heard the TR Actuator operate in and out 5-6 times. At one point I went under to confirm that it was in 2WD and the driveshaft turned. After that it became difficult to shift out of 4WD after putting it back in. I drove around the block operating the shifter repeatedly with no luck. I then tried the 2-4 switch repeatedly and it finally came out of 4WD.

So. Intermittent operation of 4WD, but I'd say the 4WD ECU is working at least as far as the TR Actuator is concerned. I'm still not certain the ADD is working right either. Should I just keep operating it over and over? Is this a case of the previous owner never using 4WD?