4WD low is a no go

Stock FSJ Tech Area

FSJ Guy
Posts: 1763
Joined: Fri Mar 15, 2013 3:03 pm

Re: 4WD low is a no go

Post by FSJ Guy »

Does reverse work in 2wd???

EASIEST way for a NO-GRINDING transferase shift: TURN OFF THE ENGINE with the transmission in NEUTRAL.
Ethan Brady

http://www.bigscaryjeep.com

Jeepless, but I still have a lots of old parts in my garage!

rocklaurence
Vendor
Posts: 2565
Joined: Sat Mar 30, 2013 6:53 am

Re: 4WD low is a no go

Post by rocklaurence »

It sounds to me that it still isnt engaging all the way. When in forward your barely in gear and then when you shift into reverse the thrust/engagement of the gear pulls away [the gears are angled but I cant think of the term]. Basically the reverse rotation is pulling the drive gear away vs pushing it in during engagement. I wouldnt put any stress on it going forward until this is resolved.
User avatar

tgreese
Posts: 7117
Joined: Fri Jun 08, 2012 6:31 am
Location: Medford MA USA

Re: 4WD low is a no go

Post by tgreese »

Does it noticeably pop out of low when you shift into reverse?

The forces on the transfer case parts are different depending on rotation direction. It's common that rotation direction changes the skew of meshing parts, and they are forced together going forward and pushed apart going backwards. Rocklaurence is referring to this property of helical gears... this happens a lot on the Borg-Warner 3-speeds. The internal bushing of 2nd in particular wears out, and decelleration skews the gear and forces the shift sleeve away from the gear, and the transmission comes out of gear.

If your transfer case was dry, and you drove it that way for a while, I would be looking at a minimum of disassemble and inspect ... since it does not seem to operate properly. Low range is an internal planetary transmission, and there is a lock plate that moves in and out of the annulus gear to lock-in low range. This plate should be available as a replacement part, and apparently it can be a service issue. Item #89 here http://www.bjsoffroad.com/NP-229-228-Sm ... _1594.html - item #6 is the annulus gear. I know this plate is available for the NP208, so it's probably available for the NP229 too.
Tim Reese
Maine beekeeper's truck: '77 J10 LWB, 258/T15/D20/3.54 bone stock, low options (delete radio), PS/PDB, hubcaps.
Browless and proud: '82 J20 360/T18/NP208/3.73, Destination A/Ts, 7600 GVWR
Copper Polly: '75 CJ-6, 304/T15, PS, BFG KM2s, soft top
GTI without the badges: '95 VW Golf Sport 2000cc 2D
Dual Everything: '15 Chryco Jeep Cherokee KL Trailhawk, ECO Green
Blockchain the vote.
User avatar

tgreese
Posts: 7117
Joined: Fri Jun 08, 2012 6:31 am
Location: Medford MA USA

Re: 4WD low is a no go

Post by tgreese »

Note there is a repair manual for the NP229 here - http://oljeep.com/edge_tcase.html This should also be covered in your TSM.

This manual shows that low range can only be reached in 4WD, and the front axle must be engaged to reach 4WD. Pretty sure an '89 does not have the vacuum-disconnect for the front axle ... but if it does, you may be prevented from reaching 4-low until the axle is connected and 4-high is fully engaged.
Tim Reese
Maine beekeeper's truck: '77 J10 LWB, 258/T15/D20/3.54 bone stock, low options (delete radio), PS/PDB, hubcaps.
Browless and proud: '82 J20 360/T18/NP208/3.73, Destination A/Ts, 7600 GVWR
Copper Polly: '75 CJ-6, 304/T15, PS, BFG KM2s, soft top
GTI without the badges: '95 VW Golf Sport 2000cc 2D
Dual Everything: '15 Chryco Jeep Cherokee KL Trailhawk, ECO Green
Blockchain the vote.

Topic author
PaulD
Posts: 48
Joined: Sat Jul 15, 2017 11:12 am
Location: Arkansas

Re: 4WD low is a no go

Post by PaulD »

Responses
- Yes, works in 2WD with no problem
- I agree that it is not fully engaging. I don't feel it "popping out" when I shift to reverse because I don't think it was engaged enough to consider it popping out. When I hold the lever hard and shift into reverse, it immediately starts grinding as if it is almost engaged but not enough for gears to mesh together
- 89 GW does not have vac disconnect on front axle
- No telling how long the xfer case has been low on fluid. I doubt PO's ever used Lo and may not have ever serviced it. When I drained it, there was about one pint in it. Probably ran this way for many miles.
- I have service manual and it shows how to overhaul the NP229

Today I drove it about 50 miles in 4WD Hi (that is OK with a 89 GW) in hopes that the agitation with full fluid might add some lubrication to any internal spots that may be sluggish and cause them to loosen up enough to shift into Lo better. Did not help. I can still get it into Lo/drive OK but still get gear grind if I try to shift into Lo/reverse.

I am assuming that it is unlikely that there is any crud buildup internally that would prevent a full shift (correct?). I am also assuming that the shift linkage is properly adjusted. I suspect it is same as set at factory. I would like to try to add some leverage to the shift linkage to try and force it into Lo but don't see any easy way to do that.

If above is true, then a mechanical problem is the only remaining cause and it will require a tear down to fix it (correct?). If I have to go the repair/replace route, I have 2 options:
1) Repair my existing xfer case. I cannot do it myself and I have no clue if there is a mechanic anywhere close who knows how to repair the NP229.
2) Swap in another NP229 from my 88 GW parts vehicle. It drives but have never tested 4WD. PO messed with front axle gears and it has no front drive shaft so I have no way to test it in current vehicle. Would need to swap it and hope for the best.

Assuming option 1 can be done correctly, what should something like that cost?
User avatar

tgreese
Posts: 7117
Joined: Fri Jun 08, 2012 6:31 am
Location: Medford MA USA

Re: 4WD low is a no go

Post by tgreese »

PaulD wrote:...
I am assuming that it is unlikely that there is any crud buildup internally that would prevent a full shift (correct?).
Seems unlikely. More likely that running it dry has worn out the internals enough so that it won't stay in gear. As mentioned above, the lock plate moves into the annulus gear to hold it stationary and engage gear reduction through the planetary gears (item #4 in BJ's drawing).
I am also assuming that the shift linkage is properly adjusted. I suspect it is same as set at factory. I would like to try to add some leverage to the shift linkage to try and force it into Lo but don't see any easy way to do that.
Do you have the 1989 TSM? That will give you the procedure for checking the linkage. You need the book for your year, since the free document I linked above includes the vacuum disconnect axle ... so it won't give you the right procedure.
If above is true, then a mechanical problem is the only remaining cause and it will require a tear down to fix it (correct?). If I have to go the repair/replace route, I have 2 options:
1) Repair my existing xfer case. I cannot do it myself and I have no clue if there is a mechanic anywhere close who knows how to repair the NP229.
2) Swap in another NP229 from my 88 GW parts vehicle. It drives but have never tested 4WD. PO messed with front axle gears and it has no front drive shaft so I have no way to test it in current vehicle. Would need to swap it and hope for the best.

Assuming option 1 can be done correctly, what should something like that cost?
There are several places on the web that sell rebuilt transfer cases on an exchange basis. I'd guess the cost for the part would be between $500 and $1000. If you have to hire somebody to do it, a reman comes with a warranty, and your mechanic would probably want to go that route. If you really want to rebuild your transfer case, you might try asking on your local Jeep/4x4 forum for a shop or mechanic that would be willing to repair your case.

JMO - the first thing I did when I bought my Jeeps was to purchase the TSM for that year. The year-specific information is invaluable.
Tim Reese
Maine beekeeper's truck: '77 J10 LWB, 258/T15/D20/3.54 bone stock, low options (delete radio), PS/PDB, hubcaps.
Browless and proud: '82 J20 360/T18/NP208/3.73, Destination A/Ts, 7600 GVWR
Copper Polly: '75 CJ-6, 304/T15, PS, BFG KM2s, soft top
GTI without the badges: '95 VW Golf Sport 2000cc 2D
Dual Everything: '15 Chryco Jeep Cherokee KL Trailhawk, ECO Green
Blockchain the vote.

Topic author
PaulD
Posts: 48
Joined: Sat Jul 15, 2017 11:12 am
Location: Arkansas

Re: 4WD low is a no go

Post by PaulD »

I do have the TSM. However, I have discovered something that may be the culprit. I was under the dash trying to get cruise control working and I noticed that the Hi/Lo arm was very close to the floor mount for the drivers seat. I tried the shift into Lo and it appears that the Hi/Lo lever may be hitting the floor mount and preventing it from its full movement. The PO installed new carpet and removed all the seats in the process. He may have remounted the drivers seat too far forward and created some interference. I am going to pull the seat out and see if it can move back a bit. If not, I will do a bit of grinding on the mount where it appears to contact the Hi/Lo arm to give the Hi/Lo are a bit more room to move. It will be a few days until I can do this. I am currently trying to get my cruise control to work.
User avatar

tgreese
Posts: 7117
Joined: Fri Jun 08, 2012 6:31 am
Location: Medford MA USA

Re: 4WD low is a no go

Post by tgreese »

Sounds possible. Good luck!
Tim Reese
Maine beekeeper's truck: '77 J10 LWB, 258/T15/D20/3.54 bone stock, low options (delete radio), PS/PDB, hubcaps.
Browless and proud: '82 J20 360/T18/NP208/3.73, Destination A/Ts, 7600 GVWR
Copper Polly: '75 CJ-6, 304/T15, PS, BFG KM2s, soft top
GTI without the badges: '95 VW Golf Sport 2000cc 2D
Dual Everything: '15 Chryco Jeep Cherokee KL Trailhawk, ECO Green
Blockchain the vote.
Post Reply