Posi-Lok question

[Gil1951]

Hi All,

Got a question about a posi-lok type cable modification to eliminate the vacumm activated front diff engagement!
I have a 99Blazer LT with the NV236 Auto 4 hi 4 low .

If I change over to this type of front axel engagement system, is there something I have to do to the vaccum solinoid so it will still "talk" to the TCCM and allow the T-case to shift as it normaly would ? The front axel position sensor would remain unchanged!

Sure would appreciate any help from anybody who has done this change.

Thanx

[old_master]

If it involves an electric solenoid to engage the axle, the vacuum line to the original switch should be plugged. Do you have a link to the kit?

[Gil1951]

Yes I would obviously plug the vacumm line . What i was wondering about was the electrical connection to the vac switch which "talks" to the TCCM! Do I put a jumper on it so the TCCM thinks it is still doing it's job! I would have to do this as well for the front axel sensor if I wanted to run it in 2w lo !
Thanx for posting the link !I am making my own using a spare locking aircraft throtle cable that I have! Cost to me is a big $0 and about an hrs' work!

Gil

[old_master]

OK, I see. The vacuum solenoid on the firewall receives a command from the TCCM to apply vacuum to the actuator under the battery tray. You could plug the manifold vacuum line at the solenoid, and use the signal from the TCCM at the vacuum solenoid to command your solenoid for the axle shaft lock. The switch on the axle housing you won't need to do anything with. Your solenoid to operate the axle lock may draw more current than the vacuum solenoid, so I think I would use a relay to operate your solenoid. The TCCM may not be able to handle the extra current, I wouldn't take the chance of toasting the TCCM.

[Gil1951]

The axel will be locked by the manual cable! The axel collar position sensor needs to tell the TCCM that the axle is locked so it can complete the shift!( from what I have read in this forum) What I was needing to know was wether the vacumm solinoid circuit needs to be modified so it can also tell the TCCM " my job is done".

Thanx Gil

[old_master]

When you select 4WD, the TCCM commands the vacuum solenoid to apply vacuum to the vacuum actuator under the battery tray. It also commands the encoder motor on the transfer case to shift into 4WD. When the axle engages, it activates the switch on the axle housing and you're good to go... in 4WD. If the switch on the axle is engaged constantly, when you select 2WD the TCCM will comand the encoder motor to 2WD and turn on the "Service 4WD" light on the dash. The TCCM will not allow the encoder motor to shift back into 4WD until the axle housing switch is deactivated. The system all works together, if the TCCM "sees" a problem, it will not allow 4WD to engage.