4WD not engaging all the time.


Asked by Oct 18, 2013 at 01:00 PM about the 2001 Dodge Ram 1500

Question type: General

I have an 01 Ram 1500 ext cab with a 5.9 auto. My 4WD has been actin up. If the truck
is sittin still, the 4WD won't engage in HI or LOW. It seems to only engage if I'm drivin
down the road at normal speed. When at normal speed I can get it into 4HI. The only way
to get it into 4LOW is to 1st get it into HI and then stop and shift it into LOW. What's
causin this?

14 Answers

Chris McGee

I think there is a vacuum actuator for the fork in the front diff to lock it, see if it is holding vacuum or if the diaphragm has a pinhole, also the transfer case has a vac solenoid on top.

7 out of 7 people think this is helpful.

I checked the vacuum lines and they seem to be fine. I've pulled'em off and they're workin pretty good. I did this on both the transfer case and the front axle. I'm not sure about the diaphragm. I didn't know if maybe the motor on the axle was gettin weak or not. It didn't seem to do it until after I changed the tranny.

5 out of 5 people think this is helpful.

what abt. the tire sizes? ALL need to be the same. Wrap a string around the tread in the center to measure the circumfrance. all should be really close to the same. Jeeps with the 242 t-case,all tires have to be within 1/4 in. If not, one axel will spin at a different rate than the other causing a binding in the system. If you can raise vehc. off the ground, and see if the system works properly. If so its the tires. NOTE dont try to engage 4wd while tires are spinning, as normally all tires are spinning at same rate whie driving.


All 4 tires are the same size and new. I won't run different sized tires on my vehicle. The 4WD just won't engage all the time unless I'm drivin down the road. And even then I'll sometimes have to let off the gas quickly to get it to engage. Of all the 4WD's I've had, I've never had any of'em act this way.


My brother had one, the ft. axle motor seems to be one of the weak points.the transfercase locks in manually, but the ft. axle locks in by vacuum. This is usually the problem point. make sure you have good vac going to ft axle motor. You may need a vac. gauge to ck for any leaks. does the a/c controls work properly? Does it change to defrost on heavy accell? are the rubber ends the plug onto ft. axle motor swollen and soft due to oil being on them?

5 out of 5 people think this is helpful.

Everything on the truck seems to be good. That's why I was wonderin about that motor on the front axle. I'll just change it and see what happens. Thanks.

2 out of 2 people think this is helpful.

Use a vac pump to test it. Does it hold vac? how easly does it slide. stick a piece of hose in it and suck on hose. it should slide rather easly

Todd Evans

I have a 98 Dodge Ram 1500 that I can not get the 4 wheel drive to engage. I can spin the front drive shaft in 2 wheel drive and when I put it into 4 WH High I cannot turn the front drive shaft. Also when the A/C is on and I heavy accell it goes to defrost.. I think I have a vacuum issue. Any help would be great.

18 out of 18 people think this is helpful.

On your Sun cider you can usually find the directions for shifting you need to be moving, it what it should say. However it doesn't say wherever in gear or not.


Defrost is the default setting for the heater/AC control panel in case of a vacuum leak (as a safety feature, since you need to be able to see through your windshield). My '97 Ram 1500's cruise control module was one huge vacuum leak --the electric solenoids inside were all corroded (common problem, since they're poorly sealed). If your cruise control also doesn't work, there's a good starting point. Unhooking the cruise control module and plugging the open port got vacuum to the transmission, but still not to the solenoid on the front axle, until a clogged vacuum line to the solenoid was found and unclogged. With those two corrections (and no new parts), my 4WD now works great (for the first time in years!).

7 out of 7 people think this is helpful.

Hi guys I have a 98 dodge ram 1500 and when I put my 4wd the front wheels won't spin but the drive shaft will

10 out of 10 people think this is helpful.
Douglas Runnion

I have a 99 dodge 1500 I can't get it to lock in fwd changed actualwader and control switch I have vacuum up to the front of the transfer but not to the fronted took metal lines off and there clear what do I check nexts

4 out of 4 people think this is helpful.

I have an 99 Ram 1500 ext. Cab 4WD i used the 4wd 3 times with no kind of noise grinding etc. Then i went to use it one day and it would not lock the front axle in. I had a friend watch under the truck and thd front drive shaft was turning but not the front axle. I pulled the front cover off to check all the gears everything looked brand new did not see anything wrong so i put new gasket and sealer on and refilled with gear oil. Took it down the road for test drive 4WD worked perfect. The next day a friend called me to pull him outhe was stuck 4WD would not work the front axle would not pull. Luckly mytruck it full positive traction it help. I'm lost don't know what to do. I have owned Dodges before but this is my first 4WD Dodge any ideas please help i just bought the truck about a month ago can anyone help me out. Thanks

1 out of 1 people think this is helpful.
Bob McMillan

i recently bought a 99 ram 1500 and I too am having the same common problem. what I believe it is, is the vacuum line going into the actuator on the front axle or the actuator itself. I had a repeating problem with my chevy s-10 and a similar system only the actuator was under the battery box on the fender

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