Patrol GQ Auto - RE4R03A - Missing Gears Diagnosis and Repair
Hi all,
As I mentioned in my 'Member's Ride' post a week or so ago (http://www.nissanpatrol.com.au/forum...-Roof-GQ-Wagon), my recently acquired GQ Safari has lost some gears in the auto transmission :(.
Having not had it for very long, nor having had an auto before, I had no idea what gears it had dropped. When I bought it the oil in the dipstick looked and smelt good so in a fit of vain hope I wondered whether it was 1st and 4th that I had lost, meaning it could be a solenoid in the valve body or simple electrical fault.
Out with the multimeter and service manual I checked all electrical components (solenoids, switches etc.) against specification. All was fine. Next, I drove around checkin the solenoid feed from the Transmission Control Unit (TCU) but again the electrical side was all behaving nicely to spec. Damn!
Next, I thought hmmmm....maybe its a stuck solenoid (more hope rather than anticipation!). So, I got some fresh ATF, filter kit and valve body gaskets and start to strip down the box with it still on the truck to rebuild the valve body, but found this in the pan.....
http://www.nissanpatrol.com.au/forum.../2012/07/9.jpg
And that signalled then end of my hopes it was minor electrical fault! lol
Looked to me at this point that some bands or clutches had been melted at some stage by overheating. It also smelled burned to all hell. Taking a peek up into the tranny sump I also notice that the reverse clutch brake band is burnt up and has no friction material left on it. This pretty much nails the problem as being a lack of 2nd and 4th rather than 1st and 4th (brake band is required by 2nd and 4th) so at least I know what I am dealing with.
So at this point I kind of know the job is going to be a little bigger than I thought. So the plan changes to this:
1 - Rebuild valve body and check all components.
2 - Remove transmission from Patrol.
3 - Strip transmission and check all parts for wear against the service manual.
4 - Order and replace the required components.
5 - Put box back in patrol.
6 - If it works again, put on a transmission cooler.
7 - Drive it for a bit.
8 - If it is still good get a Nomad valve body from Wholesale Automatics and do a DIY lock-up torque converter mod to leave me with a solid box.
Thats the plan anyway! I am going to be doing it all myself.....mainly just for the hell of it! I think I might be mad! I will update this thread as things pro/regress! :D
RE4R03A Valve Body Rebuild
Started by rebuilding the valve body to standard spec. First job was to drop off the valve body from the AT. Here it is on my bench:
http://www.nissanpatrol.com.au/forum...2012/07/10.jpg
Was full of horrible black gunge which I presume is clutch or band material. Gaskets are very fragile as well. Cracking the valve body open is piece of cake:
http://www.nissanpatrol.com.au/forum...2012/07/11.jpg
The only things to be careful of are the orifice check valve, a little filter that nestles between one side of the valve body and the separator plate and a number of ball bearings (9?) that sit within the valve body assembly. The oil galleries within the valve body were in some places very gunged up so I set to work with degreaser and a toothbrush:
http://www.nissanpatrol.com.au/forum...2012/07/12.jpg
All the valves themselves were removed and packaged up in bags and envelopes so they didn't get lost. Getting the valves out and back in again is a fiddly process that needs some patience. I wouldn't say it was difficult though.
Re-assembly was the reverse of disassembly. Valves went back in one by one before I put new gaskets on between the upper and lower valve bodies and the separator plate. All the valves were liberally lubed with new ATF on reassembly.
The solenoids then got a full work out (clean down, resistance check with multimeter etc.) before being bolted back on the valve body along with the cable supports and hydraulic pipe protectors. Again plenty of ATF was put around the solenoids and seals to ensure all sealed well.
http://www.nissanpatrol.com.au/forum...2012/07/13.jpg
Given that I don't plan to put this back in until the rest of the rebuild is done, that pretty much signals the end of the valve body part of the job. All that is left is to put on the oil filter unit and bolt up the valve body and oil pan to the (yet to be rebuilt) box.
The rebuild of the valve body was pretty easy. I am reasonably confident it will work :eek:. I reckon if you have AT troubles and are lucky enough for it to be a valve body related problem then most could tackle this. It probably took me about 4-6 hours all up over two evenings.
RE4R3A Removal and Disassembly
So, with the valve body removed (and rebuilt) and the brake band the apparent culprit for the loss of 2nd and 4th, me and mate start to drop the box. First up we jack up the truck at the front, drop both prop shafts and disconnect all the electrical cables in the engine bay. I managed to borrow a trolley from work to lower the box on that is pretty much the same as a gearbox jack. It fits the bill except that it wont drop low enough to allow us to drag the box from under the truck. However, it gets it close enough to the ground that with cunning use of a series of chocks we managed to lower it manually the last 200mm (with a few heart in mouth moments!).
Daft things we forgot:
1 - The exhaust bracket on the side of the N/S gearbox mount.
2 - The four bolts connecting the torque converter to the flex plate (essentially the auto equivalent of the flywheel).
Once we remembered these last few bits dropping the box off was pretty easy. Our job was made harder by not being able to jack the truck up as high was we would have liked due to the roof in the garage at my rented townhouse. Definitely recommend a proper gearbox jack if you can get one.
Here is the truck jacked up with the makeshift gearbox jack in place:
http://www.nissanpatrol.com.au/forum...2012/07/14.jpg
Few hours later and the box is out and on the floor:
http://www.nissanpatrol.com.au/forum...2012/07/15.jpg
Took us most of a day (in between snags and beers) to drop the box. Next step is to strip the unit down and have look at the insides....
