Question 1: How many posts do I have to have before I can start a new thread?
Question B: Has anyone encountered issues where sometimes 4wd works just fine, and others where it won't go into or come out of 4wd?
I bought my sister's old 2001 SR5 from her a few weeks ago (she bought a 2017 SR5) and have been using it as a DD to keep miles off my truck. Last summer she asked me to show her how to use the 4wd system, so we drove down the street to a dirt lot and I told her to press the 4wd button on the side of the shifter (H4F). The 4wd indicator lights started blinking and never quit until I crawled up under it and tapped the front diff actuator with a hammer and socket extension while she pressed the 4wd button. That freed it up and I told her not to mess with 4wd until the front diff actuator was replaced.
Well, fast forward to today and I decided to go mess with the 4wd system for a few minutes to see what exactly it does, and to see if the center diff lock would engage (we hadn't tried that last year). Surprisingly, it went into and came out of 4Hi, center diff locked with no trouble. Same for 4L,locked. So I tried 4H again and got flashy lights before I could get the center diff locked. Shifting into and out of 4H and 4L and transmission in and out of drive would sometimes get everything engaged and disengaged, sometimes it wouldn't. Eventually it got to the point where it wouldn't come out of 4wd, but the center diff lock seems to work like it should. I turned the car off to go inside and get ramps and a hammer to tap on the front diff actuator, and when I started it back up and drove it up on the ramps, the 4wd indicator turned off and everything appears to be in 2H.
I can hear relays firing under the driver's side kick panel and clunks from the transfer case (usually) but the 4wd function is intermittent. Reading through some of the threads linked in this one, it sounds like the 4wd system either works or it doesn't, but I haven't seen anyone talk about intermittent function.
Anyone got any insight? I'm going to go back outside in a minute and mess with it some more to keep better track of the order in which things happen to see if I can isolate what makes it work and what doesn't.
Sorry for the novel....
Well, I have some updates on this. I went outside and tried to run through all combinations of 4wd modes and took notes on what I did.
Trying to get 4Hi, center diff unlocked:
If the vehicle is stopped, AT in drive, it will not ever engage. Turning 4Hi off usually will work, but once I had to shift AT to neutral to get back to 2wd.
If the vehicle is rolling, AT in drive, it will sometimes engage if I shift AT to N while vehicle is still rolling. No issues switching back to 2wd.
Trying to get 4Hi, center diff locked:
With the vehicle rolling, AT in drive, it usually will will switch in and out of 4Hi with center diff locked ok. Once it would not go into 4Hi or back to 2wd until I shifted the AT from D to N and back to D.
Trying to get 4Lo, center diff unlocked/unlocked:
Usually works as long as long as vehicle is rolling. Sometimes it didn't want to shift back to 2wd until I shifted the AT from D to N to D.
Observations:
I managed to get the vehicle stopped in a sweet spot, with AT in N, where I could shift through all modes without trouble at all. I mean, no issue whatsoever. I went from 4Hi, CD locked to 2hi ten or eleven times, same with 4Lo, CD locked. It seemed like all the gears and splines were perfectly aligned and it shifted smoothly in that spot. As soon as I shifted AT back to D and moved the vehicle, I had to sometimes shift the AT in and out of N/D to get 4wd or 2wd. Always a pretty stiff clunk from the drivetrain whenever it finally drops into whatever mode I'm after. Center diff lock did not malfunction at all. This leads me to believe that all the actuators and switches work, but maybe one of the 4wd actuators is getting weak? It
is a 16 year old vehicle, after all.
I also noticed that sometimes when I was having trouble shifting to or from 4wd, a few seconds after getting into one mode or the other I'd get a weird buzzing noise from under the dash somewhere and then a small clunk from the transfer case. No idea what that is.
I should add that I did not crawl up under the vehicle and turn the front driveshaft by hand or try to turn the vehicle to "feel" if it's in 4wd. It's raining and I don't feel like driving out of the city to find some dirt so I can drive in circles. I don't know if it ever truly was in 4wd, but the indicator light said it was and I got some pretty solid clunks out of the drivetrain, so stuff was happening.
tl;dr: 4hi/4lo, center diff lock will always eventually work, just have to be rolling and shift transmission in and out of gear a couple times if 4wd doesn't want to cooperate.
Anyway, if anyone has experienced this or has any insight on what might be going on here, I'd love to hear it.
Thanks for reading my dissertation on how my 4wd works, haha.
