4wd question

[spdy0001]

I am about to pick up my 91 sport 5 speed and I have a question about engaging the 4wd system. On the test drive I listened to my father because I have never driven a 4wd before and he said that while were were going on the highway about 50mph I could just hit the 4wd button. I did and hear/felt a slight clunk and then I could feel more resistance under the truck. I drove like that for about 0.5mile and then turned it off.

Was this bad for it? After purchasing it I will always stop to engage the 4wd, but I was just wondering what the proper technique is for this truck.

 

[DeRocha]

The 4x4 system is shift on the fly. This means you can engage 4x4 at any speed (but it is recommended that you're going under 50mph). The system allows this to happen because the Transfer case has an electromagnetic clutch (sort of like a clutch in a std transmission) which will slowly bring the front drive shaft up to the speed of the rear shaft before locking them together. To engage 4x4 Low you must be in park or neutral and going under 3mph (you may also need to have your foot on the brake as well; If not the system will ignore the button press for 4L; This is prevent damage to the transmission and other components because low range really multiplies the torque.

It is not recommended that you engage 4x4 on dry pavement because of torque wind up. Torque wind up is a stress on the 4x4 components that is not relieved. There is no problem when you're off road or in snow because any additional torque will cause one wheel to slip/spin faster than the other Thus relieving this torque. When you travel on pavement the traction per each tire is much greater and it is very unlikely you're going to spin your tires. As a result the driveline will build up this additional torque (much more noticeable when trying to make turns)... Anyway I engage 4x4 a few times per month whenever it is raining to help keep the system in good and ready working order.

Follow the link in my sig line to see an animated view of how 4x4 and other functions work..

 

[briwayjones]

If I remember correctly the older 4wd systems like the '91s you're supposed to be going 20mph or under to shift on the fly? The newer ones you can shift at a higher speed. And also I believe the older systems weren't engadged by electro-magnetic clutches but by another manner? I think this was talked about in the 2wd-4wd brown wire mod thread.

 

[TPLYNCH]

SPDY - If your Ex still has the automatic hubs, don't forget you have to back up ~ 15ft to disengage them after you've come out of 4x4. You can run with them still engaged for a while, just causes a little extra wear and tear and drag if the are still engaged.

 

[spdy0001]

Well I drove it about 5 miles back to the dealer and never backed up and it seemed to drive as if it was not engaged. When I go to pick it up I have to back it up to get out of the lot. I will do that in the future though

 

[Christobal65]

If I remember correctly the older 4wd systems like the '91s you're supposed to be going 20mph or under to shift on the fly? The newer ones you can shift at a higher speed. And also I believe the older systems weren't engadged by electro-magnetic clutches but by another manner? I think this was talked about in the 2wd-4wd brown wire mod thread.

Manual on my 92 says i can engage 4x4 at any speed below 55mph...then again if you are going 55 you really dont need 4x4

 

[F14CRAZY]

Screw what the manuals say. 50 or 55 mph is WAY to fast for the Touch Drive system to be engaged at, especially if the hubs are not engaged. Seriously, I'd say that 20-25 is the max to engage. Disengage speed doesn't matter. The max speed I've had mine spinning up to was about 40. It was on the freeway and snowing like heck.

 

[DeRocha]

Well I drove it about 5 miles back to the dealer and never backed up and it seemed to drive as if it was not engaged. When I go to pick it up I have to back it up to get out of the lot. I will do that in the future though

The wear and tear of driving around with the hubs locked is very minor. The biggest benefit of unlocking the hubs is in Fuel savings (maybe 1-2 mpg).

...I believe the older systems weren't engadged by electro-magnetic clutches but by another manner? I think this was talked about in the 2wd-4wd brown wire mod thread.

See Brown wire mod thread for a detailed write up.