Tach reading high after messing with 4x4 engagement motor. Coincidence?

[Moford]

I posted previously regarding my 4x4 switch not engaging. To make a long story short...i took apart the engagement motor as per the link provided on this site. I went through everything and found many of the same probs as the others. Earlier in the day i could hear the motor trying to spin as i pressed the button. However, after taking it apart and reassembling it, it won't turn over. When i remove it from the transfer case, i had a friend press the switch and found that the motor tried to turn(i could feel it kick) but it didn't spin the gear. After repairing the worn stopper, cleaning the armature etc...i replaced the motor. Not only does it appear that i'm not getting power to the motor, my Tach is reading 4000 even when it's at idle. Are these two problems related? Thanks for all your help. This site has been so helpful.

 

[Opera House]

Worn stopper?

What is that? Did you remove the gear with the encoder switch? I have found that most problems are from lube drying out in the bearings. Remove the gear so the motor is free to spin. Hook the motor to 12V through a brake light to limit current. Motor should easily spin in both directions with this reduced voltage. If not the bearings are the problem. If it won't work with the lamp in series, it won't work in the car. Motor is driven by electronics with a current limiter. Too much current and it just shuts off. I've had to polish shafts and wotk in lubrication in order to get the current down. People forget how hot the transfer case gets. When I first opened the switch cover, I found chunks of what I thought was plastic gear. It was actually dried grease that was hard as a rock.

 

[VBVA]

Cleaning up the t-case motor like that shouldn't cause your rpm's to run so high at idle, since you aren't moving the tranny is essentially not engaged. Now, it could effect your rpm's while you are moving if you damage something else, but at idle it sounds like something else is wrong.

I didn't want to mess with my only t-case motor, so I went out and bought another one from a junkyard that works, so now I have two to work with. Maybe you could try something like that next time.

 

[Moford]

I did remove the gear with the encoder switch, i believe thats the gear the meshes with the actuator on the motor. That's where i found the broken plastic stopper? I thought i was yellowish orange dried grease at first, but after removing the gear, clearly saw some larger pieces that fit around the metal screw as a stopper. Maybe i'll dig back in and see about lubing it up in there.

 

[VBVA]

What size Torx Tamper Resistant Bit did you use to get those screws off?

 

[SLewis]

Finally I found someone with the same problem I have. My tach reads 3800RPM at idle and when you rev the engine it will only go to 4000RPM's. The tach was reading like this when I got the Ex. When you turn the key off the needle goes to zero.

I have replaced the elect t-case with a manual one, BUT if you figure out what is causing your tach to read like that please let me know as it might fix mine also.

Good luck.

 

[Moford]

I used a T20 tamper resistant socket. Mine came off easily. I don't imagine the tach reading is hurting anything other than my ego right now...but i'm certainly frustrated that my efforts on the t-case motor failed, then the tach went south. Can't help but wonder if i did something to cause it.

 

[VBVA]

Thanks for the tool help, I got one last night and tightened up those stupid screws...

Don't worry so much about the t-case, I don't think anything you did caused the tach to jump like that. Since you didn't physically remove the entire t-case from the tranny, there really isn't any way to cause the rpm's to run so high at idle. It is a delicate process too that takes nimble fingers. Just take it as a learning experience and know that next time you have to do this, you are one step closer to complete success...

 

[Moford]

Thankfully i finished up with the t-case acuator motor last night. It seems that i didn't fully seat the armature in the motor by turning it counter clockwise. After doing so i replaced the motor and tried again. It worked once off the t-case so i replaced. Once on the t-case it wouldn't work. I took it off and tore it down again to find that the one of the six contacts on the gear was bent. I bent it back and moved the gear a few teeth in the other direction thiniking that it was getting hung up on the the inside. I replaced and gave it a try again. 4 high worked but four low didn't. Wanting to finish for the night i buttoned it up and gave it a spin hoping that the engaging the 4hi would somehow help it get to low. To my surprise, it worked! Its functioning great. I think i'll check a salvage yard for the tach. I think i might have fried it reconnecting the battery.

 

[BuPa]

Bad Tach, shame on you!

Hi everyone,
Can we go back to the tach question without the transfer case motor issue.
A few months ago, my 92 XLT with a factory tach started to be a little mixed up. Sometimes it would work and sometimes it would sit at 3500 until the key was turned off. Now as soon as the key is in the on position it jumps to 3500 and stays there. If I am doing 65 or 70 and boot it to pass, it will go to 4000. Any ideas? Also what is the EDIS?

 

[Arke]

I'm having the same problem with it idling around 3500. It does it when the key is turned on even without the engine running.