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spline count 23 vs. 21

J

jeffrey803

NAXJA Forum User
Location
pennsylvania
hi,i'm having trouble with a 92 H.O that i put a 89 aw4 in,if my 92 has the 23 spline output and i put the 21 spline aw4 in with my 23 spline output transfer case,would the jeep move? everything bolted right up,but the jeep acts like there is no transmission underneath.it starts right up and runs fine,i kept my 92 CPS,my 92 TCU,got the 89 TCU but the connectors are different,could this be why?anyone who knows the renix,if you can chime in that would be great.TIA jeff
 
The 21 or 23 splines refers to the transfer case input, not the output. If you were able to bolt the transfer case to the transmission, they matched and you're good to go.

So everything is in place, the engine runs, and the vehicle won't move? Lemme ask a silly question: Did you bolt the torque converter to the flex plate? Before you jump all over me, I ask because when I replaced a flex plate, the friend who was helping me get 'er done thought I did that task, and I thought he did it. So we had everything buttoned up, the engine started and ran, and when I blipped the throttle I was thinking "Whoa! This thing is REALLY reponsive for a 16-year old Jeep with 165,000 miles on it." Only thing was, when I put it in gear, nothing happened.

Well ... the throttle response is generally pretty "crisp" when there's no flywheel to slow things down. :dunce:
 
The 92 TCU should work with the 89 AW4. To rule out the TCU, pull it's fuse and see if you get 4th in (OD), 3rd in (3) and 1st in (1-2). Actually if you blew the TCU fuse it would try to start in 4th gear in (OD) and seem like it's not doing anything. I would pull the tranny inspection plate and check the t/c bolts like Eagle mentioned.

Is the transfer case stuck in neutral? Can you push the vehicle with the tranny in Park and/or neutral? You did put fluid in the tranny right?
 
torque converter bolts are in,8 quarts of tranny fluid,jeep just doesn't move in any gear,revs but that's it.i will pull the TCU fuse and see if that helps,thank you for responding,i don't know if i should pull this tranny out and get another for a 92HO.
 
my linkage rod for the tranfer case wasn't on the notch,got that on,still no go.i pulled both trans cooler lines,put them in a bucket,started it up and fluid is flowing,i'm up in arms,don't know which way to turn,this is our only daily driver.anyone with any trans knowledge,please post,i will be watching this thread.it's a 89 aw4 in a 92HO cherokee aw4.i kept my CPS,TPS,Transfer Case bolted in to the 89 aw4 and kept my TCU but have the 89 TCU but the connector is different.TIA.
 
i just checked the spline input on the 89 transfer case,it's 21,are you saying that my 92 is 23 spline? would my 23 go into the 21?because it slid right on,could that be why i have no forward or reverse?it bolted right up to the 89 tranny,i reused my 92 transfer case because the 89 front cover was cracked.plus the 89 had vacuum lines and speedometer cable,which mine has the speed sensor,and no vacuum lines on it,both were 231.
 
Is the TCU fuse under the hood in fuse box by the battery?there is a fuse in there,a mini 10amp,that says trans.i looked under the dash by the TCU but can't find no inline fuse.any help,thanks
 
Don't worry about any of the electronics, if it were the CPS the motor wouldn't run, and if it were the tranny electronics it would still move, but wouldn't shift gears properly.

something is very strange though, a 92 should have a 23 spline output, an 89 should have a 21 spline. the 23 certainly won't slide into the 21, but it may be possible for a 21 to slide into a 23 and not engage. Also, the electrical connectors between 92 and 89 absolutely should be the same...

I'm still suspicious of the transfer case or tranny to transfer case connection, so I would recommend starting with removing the t-case and see if the tranny output shaft is spinning when the tranny is in gear.
 
yes it moves in park,what the hell.i didn't have to adjust the shifter cable,i used my 92 shifter cable just unbolted and bolted it back on the 89 AW4.
 
detach the cable from the shifter and push/pull it by hand (may need vice grips) and see if it will go park, reverse, neutral, drive, 3, 2-1 from the farthest in to the farthest out.

if you can get power to the wheels in any position, then it's not the t-case, flexplate, torque convertor, etc.
 
a 23 spline transfer WILL slide over a 21 spline tranny. It WILL NOT engage the splines and make it appear that the tranny is bad.

You need to match the tranny with a the proper t-case.

87 to 91 AW4 is a 21 spline output

92+ is 23 spline.
 
Last edited:
jeffrey803 said:
could i just unbolt the spline plate from the 89' 231? or change the tranny spline from my 92 AW4.
Click to expand...
you can swap the input gear from the 89 t-case to the 92 but that requires completely tearing down both cases. you also have to make sure that the gear cut on the inside of the input shaft are the same. (they should be)

changing the output shaft on the trans would also require complete tranny tear down... not recommended unless you are a highly skilled mechanic.


-or- you can simply install the '89 t-case in place of the 92.
 
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