So you want to build a tough Cosmo Auto?

Berty

Member
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Eunos Cosmo
I thought that I would make a post which outlines all of the info I gathered whilst upgrading my auto. I had to do a lot of digging to find this out and there seemed to be a lot of mixed opinions.

Specs for the Cosmo Automatic
JATCO RE4R03A
Common to Nissan Patrol & 300ZX. The box is the same - but bell housings and gear ratios are all unique.
Standard stall converter speed approx 1800-2000RPM (20B Model)

Performance of the Stock Box
My box was able to manage 230RWKW for about 2 years (70,000KM). After that, my car had 300RWKW for about 4 months (About 1000KM) and this caused significant damage to the box. Major gear slippage at full throttle was common. The bottom line is if you are in single turbo land, your box will be dieing rapidly.

Upgrade Options

Computer Upgrade
http://www.automatictransmission.com.au/release.asp?NewsId=40338

I was talking with Stuart from Wholesale Automatics about this option here are the details;

Complete Stand Alone Transmission ECU $1995 (new)

*Stand Alone Transmission ECU
*Wiring Harness
*Dash Display/Programmer
*Choose Between Full Manual Or Full Automatic At The Touch Of A Button
*Lock-Up Manual Control for 100% Engine Braking At The Touch Of A Button
*New Inhibitor Switch
*New Revolution Sensor
*Built In Temp Gauge
*Australian Back Up & Technical Support
*Made In The United States

Nissan Inhibitor Switch (comes with computer) (new)
Revolution Sensor (Comes with computer - new)
This unit requires NO software or laptop for set-up , Plug and play independent TCM.

Upgrade Option #2 - Heavy Duty "Extreme Full Manual" Nissan Patrol Valve Body
http://www.automatictransmission.com.au/release.asp?NewsId=8169

Cost was $1250 not installed. You will also need to send them your 'core' once done to receive the bond of $450 back.

Apparently this valve body has been tested up to 607HP and it manages to keep everything moving. One of the big causes of damage and wear to an auto box is the slippage caused between gear shift. By removing the slip, you reduce heat and increase the power handling ability of the box.

Going down this path will enable you to handle more power, but you will lose Drive. The car will need to be manually shifted. Lockup converter should still function as per normal meaning lower RPM whilst on the freeway. You MAY lose your cruise control.

The beauty of this modification is you can do it without taking to box out. No further internal modification is required to run the valve body. The only issue is you need to be sure that your 20+ year old gearbox is healthy to begin with. A manual valve body like this is not a magical cure.

Upgrade Option #3 - Full rebuild with shift kit
The idea behind a shift kit is that it increases the line pressure inside the trans meaning less slippage between changes. You retain Drive in most instances. The box will handle more power and is probably the best compromise between all-out power and driveability. The only issue is, by the time you remove the auto and fit the new shift kit, you have already spent a fair bit of coin and may as well go the whole way!

"Transgo" make shift kits for this box. I have never used one, however I hear that they are pretty common in Skylines which still run an auto. If you are getting the box rebuilt, I guarantee that you will need new trans mounts. At the moment, Mazda has them in stock. The series two cars also require an extra plate which is about $250 on top of the mount price which is about $90. I don't have the part numbers on me, But 'Dazda' at Gosford Mazda should be able to help you out.

A new seal kit will need to be put through the box as well as new friction materials. There is no point going to Kevlar bands at this stage so long as you are sub 250rwkw. I would expect the total cost to be somewhere around $2500AUD including labor and parts.

Upgrade Option #4 - Full Rebuild, Full Manual, All the Fruit.
You have two choices with this option - go with a 3 speed manual valve body with electric 4th OR go with a full 4 speed valve body with manually selected 4th. If you go with the three speed option, you can retain the factory shifter, however you will need a switch to engage 4th. You will also need to disable the Auto ECU for both of these options. If you are running a factory ECU, this upgrade is not for you!

I personally went with the 4 speed valve body because the main straight at Queensland Raceway can be done at more than 200KPH. :) As this is the option I went with, I can go into more details.

I opted to purchase the upgraded parts from KEAS in Australia and left the installation and rebuild to a local auto workshop. As the factory shifter would no longer work, I opted to go with the B&M Pro-Ratchet.This shifter is not for everyone and it is most certainly not for an every day car (three point turns are painful). You way also have local laws which prevent you from using this shifter on the street because of the lack of an illuminated gear indicator but there are ways to fix this.

The KEAS valve body can be ordered with or without the transbrake option. Unlike the valve body listed above, this one requires significant modification to the gearbox internals - but this is a good thing! Unfortunately, there is no reverse pattern option from KEAS. After talking with KEAS they explained that they had issues in R&D with reverse pattern valve bodies for the RE4R03A and advised to stay away from them. To do this upgrade you will need the following;

Manual Valve Body - Approx $1000 -$1250 depending on options.
Kevlar Intermediate Band & Billet Intermediate Piston Servo - Approx $300
B&M Pro Ratchet or similar 7 slot shifter - Approx $250-$350
Bigger trans cooler, especially if running a bigger stall - Approx $150
Optional - Dakota Digital Gear Indicator - $200. (This gets around some of the legality issues)

You may also want to add in a different stall converter. I wish I had now :( But more on this later.

The parts from KEAS are awesome and come with really good instructions. If you have never done an auto rebuild before, then do not contemplate attempting the upgrade yourself. The instructions may make it seem straight forward but it is a painful process.

The first thing I needed to do was install the Pro-Ratchet. If you take a look at my build thread, you will see what I needed to do. To be honest, it is a pretty simple mod. Be prepared to drill holes in your car though!

Once the shifter is installed, you can put limiting pins into the ratchet mechanism which will allow you to drive it around. You will need to install the Park Limiting Pin AND the First Gear Limiting Pin. Once the four speed valve body is installed, you can remove the First Gear Limiting Pin from the shifter.

Once you have done this, you can install your bigger trans cooler. Again, check out my build thread for pictures and instructions.

At this stage, you are coming to the point of no return! The next step is to find a competent workshop to remove the box, install the parts, modify the internals and shove it back in the car. To cut a very long story short, you are more than likely looking at around $2000 - $3000 in parts and labor to do this depending on what needs to be replaced. If you box is as shagged as mine was, expect the worst. If you are able to remove and install the box yourself, then it will be a hell of a lot cheaper.

Fact - you will destroy your gearbox mounts when removing the box. Allow 8-12 weeks for them to arrive via boat from J-land.

I won't go into details here about the rebuild specs of the box as I don't want to spam KEAS's R&D all over the net, however you will need a gearbox person who is willing to machine internals and do some Frankenstein-ing of parts. The guy who did my gearbox had never done a Cosmo, however he had a done a lot of performance RE4R03A's in his time so he was pretty comfortable with all the mods that needed to be done. The hardest thing about doing this to your Cosmo is finding a gearbox builder who passes the "attitude test". I had a really hard time finding someone in my local area who was both good and willing to give it a shot.

So what is the end result? I now have a box which will pretty much take anything I can throw at it. However, with the engine strengthened, gearbox strengthened and suspension stiffened, I have move the possible failure points to the drive shaft, diff and axles. If you break any of these parts, expect a long wait for replacements.

More info once I finish work!
 
Very thorough write up!
Why would u loose cruise control with option 1. The cruise should still work with all these options except maybe with the standalone AT ecu.

does your cruise control still work? Mine does still works with option 4.

Im not completely sure but i think as long as the factory AT ECU is still there and plugged in the cruise should work no matter what box u have.
 
i was concerned that i would loose my cruise control when upgraded the ECU, but it still worked.
then when i did the box i thought i would loose it again, but it still worked.
i think its a independant system or maybe only requiring minimal inputs.
however i cant be sure because my setup still retains the factory ECU and AT ecu as if nothing has been modified.
 
Interesting that you bring that up. I know that one of the key differences between your upgrade and mine is that I opted for the 4 speed and you opted for the 3 speed with electronic 4th right?

One thing that I haven't mentioned yet is that I lost my reverse lights, neutral safety switch and cruise control because the 4 speed conversion does not work with the sensors on the box. This is where the Dakota digital gear indicator comes into play but I will write more about this later.
 
thats right i went the elec 4th (i was told at the time by the box man that there were no 4 speed valves for my box) i dunno long time ago now.
I think thats where your problems lie.
We must also note that the 13b box is different to the 20b box. i have no idea what series it is, there was no identification at all on both 13b boxes iv had. I was told its the same as s5 & 6 rx7 auto. This difference may have something to do with the availabilty of manual valves, to be honest i have no idea.
But everything still works on my car. I just put the box back in with stock stally (lock up plate removed), installed the shifter, pluged in whatever was still there to be plugged in on the box, cut that magic wire on the AT ECU to stop the dash from flashing, and all was good.

Reverse lights work, neutral & park safety swtich works & cruise works. the only thing i lost was the key lock (where u cant take the key out unless in park).
I bet if u went with the same valve body (3 speed + elec 4th) everything would still work.
 
Good info. So it looks like the four speed option kills the cruise control, neutral safety and reverse light. The Dakota Digital box can fix two out of those three though.

This is the item in question...
http://www.dakotadigital.com/index.cfm/page/ptype=product/product_id=60/prd60.htm

I tried to install the sensor in the cabin, however you will not have enough clearance once you put the center console back in position so it needs to go on the side of the gearbox. This device can be used to show the gear position. For my box conversion this is necessary as the factory gear indicator will no longer work - it will always show neutral gear selected.
 
I cant see it being a hard fix though. after all its all just sensor/switch related for the neutral safety, and reverse.These should be fairly universal, u should be able to make it all work with whats on your box. For the cruise im not too sure, i suspect it needs a speed and gear indication which it isnt recieving in your case.
 
I cant see it being a hard fix though. after all its all just sensor/switch related for the neutral safety, and reverse.These should be fairly universal, u should be able to make it all work with whats on your box. For the cruise im not too sure, i suspect it needs a speed and gear indication which it isnt recieving in your case.

Bringing this up from the dead.

The trick to getting the cruise control to work again is to ground the relevant pin on the Auto ECU depending on what gear you are in. I managed to install the Dakota digital box. I made a linkage for it so it is mounted to the sump pan and detects the gear position based of the position of the lever on the side of the box.

Using this, I managed to wire the reverse lights up correctly to a new circuit which I made.

This wiring diagram is the key to telling the cruise control what gear you are in.

holdswitch.jpg


Right at the bottom, in the middle of the picture are the wires you need to ground using the Dakota Digital box. You can set the gear sensor to either be +12V output or grounding. I've set my outputs to ground when the gear is selected.

I run seven wires from the Dakota Digital Box (one for each position of the shifter) and wire these directly to the wires indicated in the diagram. When the gear is selected, it grounds that wire and the Auto ECU recognizes the gear. Problem solved. :)
 
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