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01grand 09-30-2013 08:32 AM

Transmission troubles
 
Hello everyone! It's good to get back on here, I have been checking in but not posting much lately, work and personal time have been very busy. Anyway, while driving down the highway the other day the MIL came on, much to my surprise because the jeep seemed to be running fine. I checked and cleared the codes, I had P0740, which is for the torque converter clutch, no speed difference detected when engaged. I noticed driving home that the TCC didn't seem to be engaging while cruising all the time, and after another 10 minutes the MIL came back. Is the TCC solenoid part of the solenoid block on the valve body or is it separate? Also, some stuff I have read says it could be a malfunctioning transmission input speed sensor, does that make sense? I figured there would be other problems if that was bad, although I'd rather replace a sensor than have to pull the torque converter. The jeep still runs fine, but once the code is set there is no lockup, so its running a few extra rpms when cruising. Anyone have suggestions at things to look at? I did check the fluid, it is still bright red and right at the proper level. Thanks!

Frango100 09-30-2013 09:04 AM

Re: Transmission troubles
 
Hi Aaron, welcome back.
The solenoid which is used for the torque converter lockup is the same as used in first gear, the LR/CC solenoid, which is part of the solenoid block. Since first gear seems to be ok, i would discard this as a problem. There are however some other (hydraulically operated)valves, which are used in the Torque Converter Clutch (TCC) system, like the torque converter limit valve, torque converter switch valve ,torque converter regulator valve and solenoid switch valve.
I donīt know yet which signal is triggering the P0740. Will look into this later today and will see if i can come up with something sensible:D.
In the mean time you better not drive for long distances, because since the torque converter will not lock up, the fluid temperature will become much higher then normal, besides the higher rpm from the engine.

Frango100 09-30-2013 09:14 AM

Re: Transmission troubles
 
Just had a quick look at the fault code and it is set when after torque converter lockup is selected there still is a speed difference between the engine and transmission (which i guess should be the transmission input speed sensor)
I would first clean all the connectors on speed sensors, transmission solenoid block and TCM and give it a try, When it returns, i would change the input speed sensor.
Worst case would be a worn torque converter clutch.

01grand 09-30-2013 09:29 AM

Re: Transmission troubles
 
Thanks for the info Frank, you're the best! I will clean up those connectors and get new speed sensors, hopefully thats the problem. I have a 180 mile drive (each way) this weekend and taking the wife's car really isn't an option.

01grand 09-30-2013 09:56 PM

Re: Transmission troubles
 
Well Frank I checked those connections, replaced the input speed sensor, and then cleared all the codes. Same codes come back. Actually it hasn't hit yet, they still are just 'pending' but I'm sure the MIL will be set again soon, my test drive was only about 5 miles tonight.

Frango100 09-30-2013 10:29 PM

Re: Transmission troubles
 
Doing some googling showed that you have to be carefull with this code. It can be that the torque converter clutch lining comes loose in pieces and that it can clog lines inside the tranny.

01grand 10-01-2013 07:57 AM

Re: Transmission troubles
 
Quote:

Originally Posted by Frango100 (Post 902125)
Doing some googling showed that you have to be carefull with this code. It can be that the torque converter clutch lining comes loose in pieces and that it can clog lines inside the tranny.

Oh that would be great! :eek: Well the rest is shifting fine so I think I'm ok, next stop is to find someone to put in a torque converter. Hmm what's airfare from Brazil to Minnesota? :D

Frango100 10-01-2013 05:51 PM

Re: Transmission troubles
 
1 Attachment(s)
But besides the torque converter, it could still be one of the control valves as well. The Solenoid Switch Valve, which directs the fluid or to the LR clutch circuit, or to the torque converter clutch circuit for example. This is a hydraulically operated valve inside the valve body. When this valve is stuck in the LR position, first gear will operate normally, but you loose the TCC operation.
All the other valves are inside the pump, so would require dropping the transmission.
I would give it a try and check the Solenoid Switch Valve (SSV). Maybe its just stuck or some foreign material keeps it from moving. You would have to remove and split the valve body for this. If you decide to go for this, i can give you some tips for opening up the valve body. You will see at the same time if there is some foreign material in the tranny pan, which could give more clues on what is going on.
Attached the valve body with item 5 the SSV.

01grand 10-02-2013 09:05 AM

Re: Transmission troubles
 
Thanks for the info Frank, I think I will do that. Yuck hopefully it would be that SSV, otherwise I would probably just start tearing the thing apart in my garage. Problem is I don't know if I have the capability for all that. I might break down and just take it in. The 2 times I've dropped the pan the fluid has been fairly clean but there was some buildup on the magnet, which should be normal right?

Frango100 10-02-2013 10:49 AM

Re: Transmission troubles
 
There is a testport on the right hand side of the transmission which shows the TCC pressure. If you could connect a pressure gauge with a long hose to this port, you could testdrive it and see if you get pressure when the TCC should be applied. If you have pressure, but no lockup, then most probably the problem is the torque converter. If you don't see pressure, then the problem could be the SSV or one of the other control valves.
And some very fine metal buildup on the magnet is normal.

01grand 10-02-2013 12:02 PM

Re: Transmission troubles
 
Thanks again Frank! Your info here is very helpful. I will definitely try that test first I think, seems the least invasive and most definite as far as whether I need a torque converter or to disassemble and clean the valves.

Frango100 10-02-2013 06:30 PM

Re: Transmission troubles
 
1 Attachment(s)
On the attached page you can see the two pressure test ports for the TCC. They are just below the upper fluid out line to cooler. You will need some special nipple to screw in there and then you will need to use a hose until it reaches inside the cabin, so that you can easily read the indicators while driving. Probably best to let someone drive, so that you can observe the indicators. You should use two indicators, one on the TCC "on" port and an other on the TCC "off" port.
During normal driving (no lock-up)there should be 35-80 PSI at the "on" port, but also 35-118 PSI at the "off"port. As soon as the TCC needs to lock up, the "on" pressure will stay as is, while the "off"pressure will go to 0 PSI. The minimum/maximum pressures depend on the line pressure (which goes from 35-165 PSI).
I just saw that a sticking SSV in LR position (so for first gear), should set a P1776 code. So in fact this possibility should be disregarded.
All the other valves are inside the fluid pump and need the tranny to be opened and the pump to be removed to get access.
Maybe wise to pass by a tranny specialist and ask their opinion as well, maybe they come up with some other ideas.


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