Jeep Wrangler Forum banner
  • Hey everyone! Enter your ride HERE to be a part of JUNE's Ride of the Month Challenge!

1 - 18 of 18 Posts

·
Registered
Joined
·
471 Posts
Discussion Starter · #1 ·
hey all,

I made some progress today... I replaced all the vacuum lines for the CAD system today, and actually got my front axle to engage...


whooo hooooo!!!!

:bop::bop::bop:

but, the 4wd light still wont come on. I will trouble shoot the vacuum switch, (near the battery), and the light bulb, and the wiring in between.

but, that isn't my problem that with which I want help today...

I have the 1990 YJ.... I thought I could 'shift on the fly' between 2wd and 4hi

does that mean I can literally shift at any speed (below 50ish?_)

and do I need to apply the clutch, when I do that?

bottom line is, I can't... I need to stop, and step on the clutch, (obviously, if I am at a stand still and the tranny is in gear).

When I do stop, and step of the clutch, I can pull the shifter back 1-click and then move forward, (or reverse), and as I start to move forwar or reverse, I can hear, a 'vvv-v-v-rrr-r-rr-r-rm-m-m-mmm-pppp'

kinda like maybe the vacuum motor starting to engage? it, the little humm/vibration thing, last about 3 seconds, ish...then is quiet..

I can tell I am in 4hi.... I can feel it....

but, more importantly, I can feel a DRAG... if I let off the accelerator, the jeep will come to halt, fairly quickly...and when I say halt, I mean stop, with a bounch and spring motion...

kinda like the brakes are on...

if I take it out of 4hi and back to 2wd, then the brake action will be released again..

I just had the rear brakes redone about 3 weeks ago...

and the passenger side ball joints were replaced last week.

not sure if the brakes are affected by the vacuum work I just did or not.. I can't think they were affected, but who knows.


please help'
 

·
Registered
Joined
·
110 Posts
The switch for the 4x4 light is on the vacuum motor. You might try jumping the two wires there and if that works the switch within the motor may be bad. If not, try checking the bulb in the dash.

The "braking action" is a new one on me. Might there be some hang up in the transfer case? Different ratios between the front and rear differentials due to a changeout? Or might the vacuum booster on the power brakes somehow be increased when you engage 4x4? Assuming you have power brakes.

Let us know what you find.
 

·
Registered
Joined
·
471 Posts
Discussion Starter · #3 ·
I have verified the gear ratios... both axles are 3.54 I have no idea how brake boosters work... that is why I am asking... im not sure if the cad is bleeding vacuum from the brakes, or visa versa... or not anything to do with the brakes...



and my CAD does not have wires or a switch... it has a vacuum line, that goes to a vacuum switch that is mounted on the firewall...

at least that is what I think is going on...that ishow it is connected now... a vaccum line comes from the back side of the CAD to that switch, and there are two wires...

I have tried to jumper those wires, to see if the 4wd light comes on, but no dice... so, I changed the bulb today, but havent tried to jumper it...

i do know that when I move the 4wd shifter, the bulb still does not illuminate.


but then again, something is now going wrong with my gauge cluster.

the oil the fuel gauge stopped working... and the oil pressure is ridiculously low...
 

·
Registered
Joined
·
471 Posts
Discussion Starter · #5 ·
i actually have one... $125 from 4wd.com it is impressive... the cable is thick. the insulation is thick... I was afraid it was going to be some lawnmower cable. or bike cable. looking thing...

if I can figure out why the brakes are giving me a problem when the axle is locked, I will probably be installing the posi lok cable sooner, rather then later... just for the security of knowing ..

but, right now.. I know the front axle is engaged because the jeep comes to a halt... heheheh

not the best way for a 4wd indicator to work.. but, at least I got 4wd...
 

·
Registered
Joined
·
1,139 Posts
i actually have one... $125 from 4wd.com it is impressive... the cable is thick. the insulation is thick... I was afraid it was going to be some lawnmower cable. or bike cable. looking thing...

if I can figure out why the brakes are giving me a problem when the axle is locked, I will probably be installing the posi lok cable sooner, rather then later... just for the security of knowing ..

but, right now.. I know the front axle is engaged because the jeep comes to a halt... heheheh

not the best way for a 4wd indicator to work.. but, at least I got 4wd...
it's almost as if the transfer case would be binding.4x4 shouldn't bring you to halt.and if you're brakes when well in 2wd.then follow the issue down the drive train. Jack stands all corners spin wheels by hand in 2wd and 4wd
 

·
Registered
Joined
·
471 Posts
Discussion Starter · #7 ·
time to get two more jack stands...
 

·
Registered
Joined
·
3,841 Posts
While you have it up on stands you need to confirm that the Front and Rear gear ratio is the same, not just what the tag says but count the turns. It really does sound like you have two different axle ratios fighting each other. Oh and if every thing works properly, You can change from 2Hi to 4Hi at any legal speed, says the owners book !
 

·
Registered
Joined
·
471 Posts
Discussion Starter · #12 ·
on the shifting from 2wd to 4hi, do I need to step on the clutch?

also, someone suggested on another forum that my front driver tire is a different size... it's a spare... so it is one inch smaller...

i wouldnt think it would make that much difference... maybe pull to one side or something, but not bring the jeep to a halt within a couple feet.

also I verified the gear ratio by pulling the covers and replacing the fluids.

the ring gears are marked/stamped with mfg information.. the last four numbers are the gear ratios... mine is 3911 or 3.54 or 3.55

i did my reading early on and didnt use 4wd until I determined the gear ratios and fluid levels and u-joint conditions....
 

·
Registered
Joined
·
3,841 Posts
One more thing is, if the CAD was robing vacuum from the Break Booster, that would make the Breaks less efficient not lock up, but the CAD uses so little Vac, that it should not have any effect on the Breaks at all, because the Break Booster gets full Manifold Vacuum.
 

·
Registered
Joined
·
3,841 Posts
That tire can make a difference when your moving, before you start to shift the ring and pinion are not turning, as you start to shift into 4Hi, if it is the tire driving the ring and pinon then thats the same thing as having different gear Ratios, and when the transfer case engages the Ring and pinion will ten be turning the same speed as the rear but the CAD can not engage the outer axle because the inter and outer axles are now moving at different RPMs because of the smaller tire. This case will be worse if the small tire is on the side with the CAD. I hope I said this so that you under stand what I'm trying to get across.
 

·
Registered
Joined
·
3,841 Posts
Then again once the CAD does engage it should just drive one tire as if you where going around a curve in the road all the time and one tire free wheel. I would like to think if all tires where the same size it would fine. Does it have a Locker in the Front?
 

·
Registered
Joined
·
471 Posts
Discussion Starter · #16 ·
no locker and yes I understand...

I understand the issues of engaging the 4wd/central axle.. but, I don't have any problems engaging... I have driven the 4wd hi on the road, and it seems to drive ok, maybe like the parking brake is on but still ok... if I step on the clutch or go into neutral, the jeep will come to a stop pretty quickly, depending on how fast I was going.. although I have never gone more then 25 mph, ish... or less... and only around the block to test it out...

until I figure this out I doubt I will be trying it again...

also, as for 4lo

I have heard and read a lot about not riding in 4lo on the road.... but, i don't think it will be a problem for a test... moving less then 10 mph, or less and in a straight line..

surely, it can't be anyworst then being on a trail, and in 4lo and approaching some obstacle... ...

but again, I doubt I will be testing any 4wd anytime soon..

thanks
 

·
Premium Member
Joined
·
3,236 Posts
also, as for 4lo

I have heard and read a lot about not riding in 4lo on the road.... but, i don't think it will be a problem for a test... moving less then 10 mph, or less and in a straight line..

surely, it can't be anyworst then being on a trail, and in 4lo and approaching some obstacle... ...

but again, I doubt I will be testing any 4wd anytime soon..

thanks

You need to sort the odd tire size out first thing. I really recommend having a complete set of four tires from the same manufacturer all inflated to the same pressure.

Testing the four wheel drive on dry pavement will introduce binding on components as soon as you turn a little bit. Having one tire slightly underinflated will do the same. Having one tire smaller than the others will aggravate this. If you then try 4LO, you more than double the forces that can be applied and will bind you up so bad that, at best you can't shift the transfer case. At its worst, you can snap something.

Do your testing on something with less traction. Gravel, dirt, grass.
 

·
Registered
Joined
·
471 Posts
Discussion Starter · #18 ·
yea, I will not be doing any more 4wd testing until I get the tires....

I am not sure about my budget. and timing... I really took a $5k hit this month from just being a good friend...

Ive been dealing with this for a while and thought I was going to see my money, but that aint gonna happen now... and Im trying to deal with that, and to stay on track with my jeep build and feeling the pinch....

Im also going to be moving soon, as I have had it with my landlord... so, I found a great place, but, there is a waiting list..... so, Im not sure when it will come thru, but Im guessing within two months..

anyways, suffice to say...my focus has been on safety while still moving towards the upgrades...

when this issue seemed to involve with brakes I started to freak out..
 
1 - 18 of 18 Posts
Top