Last post on Dec 02, 2013 at 7:15 PM
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GMC Jimmy, SUV
#49 of 313 Re: 1997 GMC Jimmy 4wd engage problems [j2ther]
Nov 29, 2006 (3:17 am)
You should have a 233 transfer case, 3 button so this is based on that. There is a vac line that runs down to the drivers side of the transfer case to a vac switch that controls the front axle actuator. Its a $15 part that I would say is the most common problem with all 92up 233 cases. Its a 3 port vac switch Motormite/Dorman #49315 and I just did a 98 same thing. Need a 7/8" box end wrench to replace and the formed rubber connector is keyed so pull it off. Hope that does it.
#50 of 313 1997 Jimmy (Internal Warning Speaker Removal)
Dec 06, 2006 (9:00 pm)
It "sounds" like i have an electrical problem!
The internal warning speaker (not sure of it's technical name somewhere inside the dash) is ALWAYS on as long as the key is in the ignition. It started last week, coming on periodically and now it progressed to non stop being all the time. i checked all fuses and they are ok, and i have no error codes displayed on my dash. Any ideas or advice? Were exactly is the speaker so i can remove it?
#51 of 313 Re: 1997 Jimmy (Internal Warning Speaker Removal) [97jimmyslt]
Dec 07, 2006 (3:12 pm)
Do you mean the key in ignition buzzer noise - if so only the 97 (your lucky day) has a known ignition problem with the ignition module (wires and connector in the steering column) but called the ign switch. Change it out and good to go.
#52 of 313 98 jimmy vacuum hose sizes
Jan 01, 2007 (8:30 pm)
I am about to replace all the 4x4 vacuum hoses just to make sure they are right. I have read that they are 5/32" and 7/32". Some questions...
1. Tis is ID, correct?
2. Silicone hoses are OK?
3. Most hoses I find are metric, that is 4mm, 6mm... research is not clear but I believe I can use 4mm and 6mm, correct?
4. Approximately how much, in feet and meters, of each do I need to replace all the 4x4 related hoses?
#53 of 313 Re: 98 jimmy vacuum hose sizes [rrrccc01]
Jan 03, 2007 (2:59 am)
4 and 6 or what my conversion came up with also but never had to find metric ones - alittle slow down here getting on world standards. Never used silicon. If a 3 button with the vac switch on the transfer lots needed but normally only about 2 feet/meters of smaller under hood are bad. Make sure you get the lines right if you run all the ones to the transfer case on 3 button.
#54 of 313 Done a lto and it is worse now!
Jan 10, 2007 (3:22 am)
RD, thanks for your reply.
Things are getting worse and worse! I have some questions but Ill fill in details first.
1998 GMC Jimmy
3 button 2 Hi - 4 hi - 4 lo
NP01 Transfer case (233?)
Original problem, TCCM needs to be rebooted on a regular basis.
Done so far in this order:
1.Replaced actuator under battery no change
2.Replaced TC sensor no change
3.Replaced TCCM with a used one from ebay - no change
4.Replaced at same time
b.Replaced Front Diff oil
c.Replaced TC encoder motor
d.Replaced vacuum lines to TC
Now no 4wd at all, 4 hi and 4 lo flash then back to 2-hi
I am stationed in the Persian Gulf and am unable to do the work myself, physical injury, but, I have a reasonably knowledgeable local mechanic that does what I tell him, that is I supervise!
1.Is this indeed a 233 TC?
2.I have seen the phrase "firewall solenoid" in the newsgroup, is this the actuator under the battery or is it a different part?
3.When my guy ran the new vacuum lines from the TC sensor, he told me one was a breather. Is this so? If not where do all three 3 hoses go? What did he miss?
4.I have seen repeated comments regarding the encoder motor, 4 hi and 4 low. Before installing the new motor we connected it to the plug and pushed the 4-hi button and it did move. So last and for all, does the TC encoder motor do anything when shifting from 2wd to 4 hi?
#55 of 313 Re: Done a lot and it is worse now! [rrrccc01]
Jan 10, 2007 (8:01 pm)
New parts installed:
TC Vacuum switch
TC encoder motor
vacuum hoses from TC vacuum switch
Front Differential oil
TC fluid (Red dexron II)
Checked vacuum at actuator under battery, none!
Hooked up direct vacuum to actuator and it does pull the cable!
So this means no vacuum from 3 port switch on TC to actuator! Further research on vacuum:
I have identified the hoses on the switch on the TC:
1 constant vacuum from intake set up
2 to vacuum actuator under battery
3 is release vent for sifting back to 2wd.
To me, this means that when the ball is pushed or released by something in the TC to either release or send vacuum to the actuator to engage/disengage the front axle. What pushes the Ball? When? I presume something in the TC moves, probably moved by the encoder motor? I hear the TC encoder motor running when pushing the 4-Hi switch.
Is it possible that the hoses were connected incorrectly to the TC vacuum switch? I know it is keyed, so this shouldn't be possible but hose 1 (constant vacuum) and 2 (vent) are the same size and could theoretically be switched and would explain why there is no vacuum to the actuator under the battery. For the sake of argument, which hose should be where, clockwise from the "key" on the switch?
Also, is it possible to install the TC encoder motor in the wrong position, i.e. the motor thinks it's in 4wd but the truck is in 2wd? I hear it run when I push the 4-hi and 4-lo switches, so it's doing something!
Last but not least, I am out here on the fringe of the world so getting parts is a battle! The last one I can think of is the switch on the front axle/diff; anyone have the part number?
#56 of 313 Re: Done a lot and it is worse now! [rrrccc01]
Jan 11, 2007 (3:49 am)
You got it. The 3 port vac switch on the TC is the most likely item to fail but its new. When in 2wd the ball on the switch bottom is down and the vac shut off while the vent line (also connected to the TC vent) is connected to the front actuator so its uncoupled the front axle. When 4Hi selected the encoder motor steps to move a fork in the TC that engages the front driveshaft and pushes the ball up on the 3 port vac switch that opens the port so the engine vac now is to the front actuator (and shuts off the vent port to actuator). How about the dash switch - I just posted 2 answers on how that works with 8 volts and TCCM watches return from switch each mode with a diff resistance value (Dorman about $35). That front coupler sensor is gm#15598481. The firewall solenoid is for autotrac 4 button cases only so you don't have. You can find most parts online at the dorman, smpcorp, or rockauto sites all with pics and many cross ref #s.
#57 of 313 02 Blazer transfer case always engadged
Jan 21, 2007 (5:55 am)
I have a 2002 Blazer 4x4 with 2wd 4hi 4lo and auto 4wd buttons the transfer case is always engaged (front drive shaft always turns) is this supposed to be that way? is there reason for concern? and if its not supposed to do that is there a common problem I should look for?
#58 of 313 Re: 02 Blazer transfer case always engadged [rodney7]
Jan 21, 2007 (6:32 am)
The 4 button Autotrac transfer cases NP236 always have the driveshaft connected by desigh so no worries. This is always spinning to accomodate the Auto4wd selection that senses wheel spin and engages power to the front differential when needed. (The 3 button cases NP233 does not and it engages when 4wd is selected)