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-   -   Vacuum shift motor inexpensive fix (http://www.wranglerforum.com/f218/vacuum-shift-motor-inexpensive-fix-87568.html)

Coyote_94YJ 04-02-2011 10:57 AM

Vacuum shift motor inexpensive fix
 
I've done this install a couple of times now. First on my old YJ and second on my Dodge Ram last weekend. It is a simple process and it costs very little.

Here's how you do it.

1) Remove the 4 bolts that secure the shift motor to the axle housing and remove the shift housing assembly(careful some 90wt will pour out so have a drip pan handy).

2) Remove the 2 "E" type retaining clips that hold the shift fork on vacuum motor and the 1 "E" type retaining clip that holds the vacuum motor to the shift housing.

3) Pull the vacuum motor out of the shift housing which will slide the shift fork off the shaft.

4) Take the shift motor to the hardware store.

5) Buy a long spring that is just large enough to slide over the shaft of the vacuum motor shaft and take it home.

6) Slide the spring onto the shaft of the vacuum motor, put the shift fork back inside the shift housing and slide the vacuum motor back inside the housing so as to fully compress the spring. The spring will be too long so make a rough guess as to how much to trim off so that the vacuum motor will go all the way back into the shift housing.

7) Once the spring is the correct length slide the vacuum motor back in and install just the 1 large "E" type retaining clip that holds the vacuum motor into the shift housing. The other 2 are no longer needed. (Yay, left overs)

8) Slide the shift collar inside the axle housing over to engage the front axle.

9) Reinstall the shift housing back on the axle housing making sure to align the shift fork up with the center of the shift collar inside the axle housing. Also be sure to add a bit of RTV gasket maker to prevent leaks.

10) Top up the fluild level in the front diff, and go for a test drive to make sure it works.

cpisani89 04-02-2011 12:12 PM

i was just gonna replace my shafts with xj shafts but this is def a good cheap alternative

NAVYCHIEF 04-02-2011 12:38 PM

i did this fix 2yrs ago. works like a champ.

Rhinowrangler 04-02-2011 02:24 PM

Thanks for the how to! Just a couple questions. When you say slide the collar over, does it go to the left or right? I'm guessing the left so it joins the two axles. Also will doing this make my front end full time posi causing it to hop on pavement? Thanks again!

NAVYCHIEF 04-02-2011 03:15 PM

move the collar to the left. i only notice any change when making extremely tight turns,like in parking lots. other than that, no problems what so ever.

Rhinowrangler 04-02-2011 03:58 PM

I got it. It works great. No more swimming for me!

Coyote_94YJ 04-02-2011 11:55 PM

Quote:

Originally Posted by Rhinowrangler (Post 1153989)
Thanks for the how to! Just a couple questions. When you say slide the collar over, does it go to the left or right? I'm guessing the left so it joins the two axles. Also will doing this make my front end full time posi causing it to hop on pavement? Thanks again!

Yes it keeps the front end fully engaged all the time as far as the front diff and all that but you won't get that jerking hopping while making turns because your transfer case will still be in 2WD and therefore the front end will still be disengaged from the rest of the drivetrain.

GrNMoNsTr--93YJ 04-03-2011 09:20 AM

just picked up some new axles for the jeep and was going to do this fix with the spare 4wd actuator i'll have from the new front axle. what are the benefits of having the front end fully engaged with this new spring inside the actuator? i love wrenching on the jeep and this would be a great opportunity to learn more about how everything works on this beast.

Coyote_94YJ 04-03-2011 11:29 AM

Quote:

Originally Posted by GrNMoNsTr--93YJ (Post 1155073)
just picked up some new axles for the jeep and was going to do this fix with the spare 4wd actuator i'll have from the new front axle. what are the benefits of having the front end fully engaged with this new spring inside the actuator? i love wrenching on the jeep and this would be a great opportunity to learn more about how everything works on this beast.

Reliability. You won't have to worry about getting out somewhere and your 4WD not working because of a vacuum leak or the vacuum motor going out.

Moroney167 04-06-2011 08:03 PM

So by doing this your basically locking in the front shaft as you would by replacing it with a TJ solid one?

IF so this is great. I'll be doing this tonight. I don't mind bad mileage or whatever. Runnin swamper tires and this jeep wil lnever see highway unless its on my 5th wheel trailer along with other mudders haha.

Coyote_94YJ 04-06-2011 08:48 PM

Quote:

Originally Posted by Moroney167 (Post 1162431)
So by doing this your basically locking in the front shaft as you would by replacing it with a TJ solid one?

IF so this is great. I'll be doing this tonight. I don't mind bad mileage or whatever. Runnin swamper tires and this jeep wil lnever see highway unless its on my 5th wheel trailer along with other mudders haha.

Exactly. :thumb:

mysic93 04-06-2011 08:56 PM

I tried your method and it is not working. ive pulled the vacuum moter, alighned the callor, its not working i have no drive to the front wheels. On jacks the front wheels spin the drive shaft, but on the ground four lo and four high dont work. No drive to fornt wheels. Any imput? did i forget something? did you forget something? Thx for the help


- MYSICKYJ & SON -

busemans 04-06-2011 09:02 PM

on jacks, does the driveshaft turn when you put it in four by four? sounds like a tcase problem

mysic93 04-06-2011 09:06 PM

It was working fine with the stock vacuum system 2 hrs ago, so i don't think it is the transfer case. In a jam, please help
thanks,


- MYSICKYJ & SON -

busemans 04-06-2011 09:07 PM

is your vacuum lines backward and disengaging the motor when you put it in 4x4?

mysic93 04-06-2011 09:13 PM

when i use the spring doesn't that bypass the vacuum lines and electrical connecter.

- MYSICYJ & SON -

Coyote_94YJ 04-06-2011 09:38 PM

Did you put the spring on the correct side of the shift fork? The shift fork should be held towards the driver side by the spring.

mysic93 04-06-2011 09:44 PM

Yes, i have installed, and taken it out and checked 3 times. the fork is over the callor pushing towards the left side. before this 4wd worked fine, just wanted to change over. plugged vacuum lines, didnt reconnect electricle switch, figured its by passed now. Just stumped while there is no drive to the front wheels.

- MYSICYJ & SON -

Coyote_94YJ 04-06-2011 09:54 PM

Here is something to try just to sort of narrow down where the problem is coming from. With the jeep on jack stands remove the shift housing assembly from the axle and slide the shift collar so that it is centered on both shafts(engaged). Without putting the shift housing assembly back on the jeep check to see if all 4 tires move when you try to drive it on the stands.

mysic93 04-06-2011 10:01 PM

i have had the front end already on jacks, after installing. When spun the front tires the drives shaft moves both front wheels. So i know it's engaged. back on ground engaging 4wd only back wheels spin on hill climb.
P.S. We live on property so it is easy to check. Me and my son appreciate your help
P.S.S. It just doesnt make since?

- MYSICYJ & SON -

Coyote_94YJ 04-06-2011 10:15 PM

Your right, it doesn't make sense. Can you do me a favor? With the front end off the ground have your son hold the driver side tire so it doesn't move, or just jack up the passenger side if the front end isn't already on stands, and turn the passenger side tire by hand and observe the front drive shaft coming from the transfer case and see if it spins in relation to you spinning the tire. If it's working correctly the drive shaft will spin faster than the tire.

mysic93 04-06-2011 10:33 PM

they are both spinning the same as the drive shaft? Still have vacuum lines and electric unconnected? although it probably doesnt matter? stumped:facepalm: dad is going to bed, we will work on it tomorrow. Thanks for everyones imput.

- MYSICYJ & SON -

Coyote_94YJ 04-07-2011 12:34 AM

Quote:

Originally Posted by mysic93 (Post 1162819)
they are both spinning the same as the drive shaft? Still have vacuum lines and electric unconnected? although it probably doesnt matter? stumped:facepalm: dad is going to bed, we will work on it tomorrow. Thanks for everyones imput.

- MYSICYJ & SON -

OK. If both are spinning then it has to be in the transfer case. When I did both of my installs I made sure that there really wasn't room for any more spring in there. In other words the spring was fully compressed with just enough room to fit the shift fork on the shaft and get the vacuum motor all the way in. And I used a fairly stiff spring. If possible can you remove the shift motor housing from the front end and take a picture of the current configuration and post it up here just so I can see exactly what is going on with it.

Something to try tomorrow. If you can...put the whole jeep on jack stands, shift into 4WD and start the Jeep and put it in gear and see if all 4 wheels spin in the air. The only thing I can think of since the front end is working is that by some strange coincidence the transfer case has decided not to work at the same time as you doing this mod.

There are a few possibilities with the transfer case.

1) The bolt that secures the shifter to the linkage rod could have came loose and isn't shifting the transfer case properly.

2) The chain inside the transfer case could have broke.

3) The nylon inserts on the mode fork inside the transfer case could be damaged or missing. I've had this happen once. I think it was around $5 for new ones and I put them in myself.

Moroney167 04-08-2011 10:20 AM

Read the directions about 20853 times before starting it so I just remembered them. Went in garage an knee I had a spring I could cut to work. Took maybe 10 minutes and I had cover back on filling with fluid again. Works AWESOME. so damn happy for this forum to be here and fix what could be a headache for $0 out of my pocket. All I can say is this jeep is so worth the money.

87yj2.5 08-21-2011 11:18 PM

so this sounds great but it wont wear out you front diff early or anything?

Coyote_94YJ 08-22-2011 09:16 AM

Nope not at all. The front diff is built just like the rear diff and you use it every time you drive and add to that the fact that Jeep designed the TJ to run the front diff that way. Besides... there is no load on the front diff since your transfer case is in 2wd.

NAVYCHIEF 08-22-2011 11:46 AM

with the left tire on the ground, lift the right side just enough to turn the wheel, CAREFULLY, while the right wheel is turned, put your finger on the collar and push it to the left until the gears mesh connecting the two axel halves. should work.

kb912 08-22-2011 05:42 PM

couple questions..

1) do you notice any drop in mpg?

2) does this mod give you full four wheel drive or do you still get the one front/opposite rear spin when you dont need them?

Coyote_94YJ 08-22-2011 06:20 PM

Quote:

Originally Posted by kb912 (Post 1498014)
couple questions..

1) do you notice any drop in mpg?

2) does this mod give you full four wheel drive or do you still get the one front/opposite rear spin when you dont need them?

1) I never checked the mpg in my jeep for 2 reasons. One its a jeep and has the aerodynamics of a brick. Second my jeep had a built chevy 350 so mileage was out the window anyway. If there is any change it can't be more than 1-2mpg.

2) The front differential is still open so you will still get differential action; ie. the left and right side tires spinning independently of each other. The only way to fix that is with a locker, spool, or a welder.

kb912 08-23-2011 12:52 AM

Not trying to sound dumb.. but to fix to say with a locker? Would that be front? Back? Or both??


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