• Welcome to the new NAXJA Forum! If your password does not work, please use "Forgot your password?" link on the log-in page. Please feel free to reach out to [email protected] if we can provide any assistance.

transmission sensor/sending unit?

R

Red River Sport

NAXJA Forum User
Location
North Texas
Looking at my trany today, I noticed some sort of sensor or some kind of electrical device on the driver's side rear of the trany housing. It seems to be covered in splattered fluid from what appears to be a pan gasket leak and I was wondering if the sensor could be shorting out, causing the trany to malfunction. Lately the XJ has been accelrating like It's pulling a sherman tank. Then once I get above 30mph or so, its fine. Just want to cover all the bases at home before it goes to the shop.
 
I've noticed a little lag in mine too...more like towing an Abrams tank. I have a suspicion it may be my rear wheel bearings.

I think that sensor you're talking about is linked to the computer somehow.
 
Should I assume that your XJ is experiencing the same problem that mine has? When the AW4 is stuck in 3rd gear, moving from a stop is slow. The engine revs to about 2,000 RPM (I think that is about where the torque converter locks up fully) and holds there until the MPH catches up then the XJ accelarates normally. Try shifting it manually to the 1/2 position and see if that makes a difference. Mine does.
 
techno1154 said:
Should I assume that your XJ is experiencing the same problem that mine has? When the AW4 is stuck in 3rd gear, moving from a stop is slow. The engine revs to about 2,000 RPM (I think that is about where the torque converter locks up fully) and holds there until the MPH catches up then the XJ accelarates normally. Try shifting it manually to the 1/2 position and see if that makes a difference. Mine does.
Click to expand...

Any ideas what the cause is? How long has yours been doing it?
 
Mine has been doing that on and off for about a month. I changed the oil and it went away for a week then came back. It is difinately heat related and gets progressively worse as I drive more on a hot day in city traffic. I uses the shift lever as a manual shift especially from a stop. Funny thing, no matter how it acts up, it never seem to slip in first gear. If I put my foot down, it would burn rubbers. Maybe that is why I have not put more effort into its repair. I will have it looked at by a professional this week. I will let you know what he says.
 
I have this same problem with mine. It seems to be taking off in a higher gear, but I can manually shift it down and it drives fine. What is the fix? Is this a range sensor?
 
BASICS--Year/engine/transmission/etc.?
 
87 Cherokee XJ, 4.0 Renix, not sure of transmission, but thinking AW4. As far as symptoms. Takes off in what appears to be 2nd gear, but you can manually shift it down into first. It also appears that overdrive is not kicking in like it should. The transmission is not making any noise, shifts strong, and has been fully flushed and serviced in the past 800 miles. The primary symptoms is that it is retarded and won't choose the right gear without me babying it.
 
Oh, I pulled the transmission fuse and it looked ok. There is a button on the dash that says 'power' or 'comfort', but I have never noticed that it does anything since I have had the Jeep, so I am not sure that something isn't jacked up with the electronic controls either.
 
Ok.

First, fluid--you say it is at the right level, has been changed, is bright pink, and doesn't smell burnt, so we will move on.

Second, adjust the throttle pressure cable, see here: http://naxja.org/forum/showthread.php?t=1015963

Third, test and adjust or replace the TPS (bookmark this page): http://www.lunghd.com/Tech_Articles/Engine/Basic_Sensors_Diagnostics.htm

Fourth, unplug the TCU (or pull the fuse) and drive it shifting manually. You should get 1st in 1-2; 3rd in 3; 4th in D; reverse, neutral and park. No OD/torque converter lockup. If you get these results, that means the mechanical/hydraulic of the trans is good, and that your problem is electrical--TCU/harness/solenoids.

Nice article on the AW4: http://www.transonline.com/transdigest/magazines/1997-10/Shift Pointers/index.html
 
I hope you guy don't mind but I'm gonna hijack this thread. I think I have a Transmission problem but not sure.

To start off I have a 2001 Classic with 4.0l with AW-4 and NP231, 122,000mi.

Okay, so when I'm driving under moderate acceleration. My jeep will stall for a split second shifting from 3rd to 4th. now I didn't realise this at the time so i took it to autozone and had them run a diagnostic. Now my jeep did not throw a light so the guy said it might not work. anyways the diagnostic said I had a miss fire in cylinder 3, so I changed the plugs, (3 month old plugs) and instaled a new coil pack, just to be on the safe side. That didn't work. so next I replaced the map sensor, my 96 sport had somewhat of the same problem and that fixed it. Not this time. so I was thinking it might be in the fuel system. Priced injectors, $50.00 a pop at advanced. so I ran injector cleaner through a tank and still nothing.

So before I spend $300.00 on injectors that wont fix my problem, and drop my fuel tank and replace my filter, I was woundering if it could be my tranny. Now I've owned my jeep for about a year, and I have not changed the fluid or filter (But on my list). Could this help? I'm scared to take it to a shop for fear of BIG $$$$! but I'll do what I have to. I love my jeep.

I was also told it could be my crank trigger or my torque converter could not be locking up...

Any help would be greatly appreciated.

Oh I don't know if this helps but its also lifted 3.5 in and 31in bfg's with stock gears (4.10's w/ lockers in the works)

Thanks Bob.
 
Great information Joe!!! I really like the article on the TCU. I didn't know there was a secondary fuse on the TCU unit. I didn't even look at that one.

I'm not really sure if I understand why the TPS would be affecting the shifting though.
 
Red River Sport said:
Looking at my trany today, I noticed some sort of sensor or some kind of electrical device on the driver's side rear of the trany housing. It seems to be covered in splattered fluid from what appears to be a pan gasket leak and I was wondering if the sensor could be shorting out, causing the trany to malfunction. Lately the XJ has been accelrating like It's pulling a sherman tank. Then once I get above 30mph or so, its fine. Just want to cover all the bases at home before it goes to the shop.
Click to expand...
Assuming you're talking about the one on the transmission, not the one on the transfer case, you're looking at the output speed sensor. On 97 and older vehicles it is just a reed switch triggered once per shaft revolution by a magnet, on 98 and newer it is a magnetic pickup coil triggered 4 times per shaft revolution by a magnet. It won't short out from fluid leaks, trans fluid is non conductive and the sensor protrudes into the transmission case and is designed to be exposed to fluid.

olskoolkool said:
I hope you guy don't mind but I'm gonna hijack this thread. I think I have a Transmission problem but not sure.

To start off I have a 2001 Classic with 4.0l with AW-4 and NP231, 122,000mi.

Okay, so when I'm driving under moderate acceleration. My jeep will stall for a split second shifting from 3rd to 4th. now I didn't realise this at the time so i took it to autozone and had them run a diagnostic. Now my jeep did not throw a light so the guy said it might not work. anyways the diagnostic said I had a miss fire in cylinder 3, so I changed the plugs, (3 month old plugs) and instaled a new coil pack, just to be on the safe side. That didn't work. so next I replaced the map sensor, my 96 sport had somewhat of the same problem and that fixed it. Not this time. so I was thinking it might be in the fuel system. Priced injectors, $50.00 a pop at advanced. so I ran injector cleaner through a tank and still nothing.

So before I spend $300.00 on injectors that wont fix my problem, and drop my fuel tank and replace my filter, I was woundering if it could be my tranny. Now I've owned my jeep for about a year, and I have not changed the fluid or filter (But on my list). Could this help? I'm scared to take it to a shop for fear of BIG $$$$! but I'll do what I have to. I love my jeep.

I was also told it could be my crank trigger or my torque converter could not be locking up...

Any help would be greatly appreciated.

Oh I don't know if this helps but its also lifted 3.5 in and 31in bfg's with stock gears (4.10's w/ lockers in the works)

Thanks Bob.
Click to expand...
An 01 with a cyl 3/4 misfire is probably heat soak, not bad injectors/plugs/etc. Replacing the plugs once in a while is never a bad thing though, so don't consider that much of a waste. What you probably need to solve that code is a fan timer to keep the fan going for a few minutes after vehicle shutdown... won't fix the stall feeling when shifting though, I'm not sure what that is.

keith_b00ne said:
Great information Joe!!! I really like the article on the TCU. I didn't know there was a secondary fuse on the TCU unit. I didn't even look at that one.

I'm not really sure if I understand why the TPS would be affecting the shifting though.
Click to expand...
The TCU uses the TPS to determine how much you're jamming on the pedal, which it uses to figure out how fast you're trying to go. If it gets a wonky value it'll either think you're trying to accelerate more than you are or less than you are, so it will shift in ways you aren't expecting.
 
Here is a follow up in case it helps someone else in the future. I put a volt tester on the TPS and it checked out at 5 volts on terminal A and 0.8 on terminal C. I assumed it was working ok and moved on to the TCU. Thanks to Joe, I identified a second inline fuse underneath the dash near the TCU. It was wrapped in electrical tape with the other wiring and at first glance didn't look like a fuse. Inspection of the fuse showed severe oxidation. The fuse could not be removed. I cut out the section of wiring, spliced in a new fuse holder with 10 amp fuse and the tranny started working. Put everything back together and within an hour it was fixed.
 
Glad you found it and got it fixed!
 
You must log in or register to reply here.

Similar threads

S
Transmission repair in a jeep that caught fire
Replies
18
Views
2K
Unclewolverine
U
2
Steam around O2 sensor, engine whistle and a Cat-related engine code
Replies
5
Views
1K
89Mock
89Mock
hot_rod_hooligans
97+ fuel tank & pump/sending unit in a 96?
Replies
4
Views
1K
smokeyyank
smokeyyank
C
Any Jeepers want to wrench on my car?
Replies
4
Views
773
CheapJerokee
C
C
New Jeep...new problems!
Replies
0
Views
288
CheapJerokee
C
Back
Top