Strengthening the automatic transmission on the cheap

Most people around here already know that the VR-4 automatic transmission (code W5A51) has a reputation for sudden failure requiring an expensive rebuild. This thread is for discussion of the possibility of doing an cheap DIY fix for the most problematic part - the low/reverse wave spring. I've been gathering some encouraging information, so excuse me while I dump it here and feel free to chime in.

Below is the workshop manual courtesy of mivec.co.nz for the 4 speed front-wheel drive transmissions F4A41, F4A42, F4A51 but I believe the majority of information is useful and relevant to us. I'll also be posting up sections from the PDF for discussion.
Download the A/T workshop manual PDF

Below here is the complete parts shopping list for this fix.

Pricing as at 29/01/10 (without postage).

*Alternatively you can try sourcing aftermarket ones as follows:

Sizing: Japanese "JIS B 2401" standard
Material: Nitrile (Buna-N) 70 Duro
MR486844 replacement = 9.8mm ID x 1.9mm C/S (6 needed)
MD756673 replacement = 37.7mm ID x 3.5mm C/S (1 needed)

Optional Parts MD760146 & MD760147:
Metal seals that the workshop manual recommends replacing. These are very easy to change. However, if you are strapped for cash and your car has low mileage then you can probably skip them.

There are three main shortcomings with the A/T, all which can add up to disaster.

- the wave spring can break into pieces
- the internal filter has a manufacturing fault which can let these pieces through
- The pump gear can shatter, usually when the bits of the wave spring make their way into it jamming it.

Unfortunately without removing the transmission from the car we can't replace either the filter or the pump gear with improved items, but we can do something about the wave spring which starts all this mess.

Further reading below, it refers to a FWD version of our transmission but it is also applicable to us.

http://www.transmissiondigest.com/tech/TD200508/200508ShiftPointers/200508ShiftPointers.htm

Below are some pics taken from Club3G.com, an interesting read at that link too.

Again, this is showing a F4A51 but it equally applies to our W5A51 automatic transmission.

The first two photos show the weak spiral type wave spring that breaks, compared to the solid replacement that is much stronger.

The third picture shows the location of the wave spring in the transmission. If the transmission was still in the car this is looking in from the passenger side wheel at what is classified as the rear of the transmission.

This view shows where the wave spring sits in the transmission. Everything to the right of it has to come off first, however it isn't as bad as it seems because a lot of those bits are clutch packs which you can lift out in groups all at once. The rear cover (40) has to come off first, and is what you will be faced with once removing the passenger side wheel and inner plastic guard.

Congrats on starting the work on this.

Massive kudos if you can pull this off!!

As i queried in your other thread, Is it actually and upraded wave spring or just a direct stock replacement?

Well, the stronger wave spring is a genuine Mitsubishi stock part. It's not specifically started as being 'uprated' but it is of a very different construction to the original. In ASA it's listed as being the new part number for the wave spring. Mitsubishi seemed to recognise there was a problem with the original part and superseded it, but choose to keep things quiet for reasons we can probably guess.

The original wave spring was a thin, flat open-ended spiral design. The new one is a solid square cross-section and is in one continuous ring. It will drop straight in without any modifications being needed. So if you are asking, would we be replacing it with exactly the same part then the answer is no. It is being replaced with a much better item that has not been known to fail.

From what I can gather from discussions on here & CVR4, the idea behind the spiral wave spring was for smoother gear changes. But reports are that the solid type doesn't have any detrimental impact on the shifts.

Its solid Trev, meaning no disintergrating in the gearbox

The old boxes used a solid one, then Mitsi went to the coil to soften the shifts then changed it back again once they realised they were shite. Technically the cars should've been recalled but it would've cost Mitsi 100's of 1000's to fix them all!

When you say 'the old boxes' Dawso, are you referring to 7G or early 8Gs?

Previous models. They stopped using it in the early 90's AFAIK. They changed them in the Magnas too apparently....

Nice work Will be watching this closely.

Thanks

Who cares about slightly harsher shifts? I know I just want my box to last. Very keen to do this.

Do you know any one, or heard of any one performing this upgrade - gearbox in?

Speaking from experience, you will hardly (If not at all) notice the difference. It can be clunky when cold but thats about it.

pu-11-me said:

It can be clunky when cold but thats about it.

Click to expand...

Sounds normal to me.

A little side note...

Anyone who is having work done on their torque converter should consider getting the internal filter replaced and a strengthened steel pump gear fitted. They are all on the same side and easily accessed by removing the torque converter housing. However you will need an alignment tool to get the pump back in.

I'm not sure with these parts whether the genuine items are now improved or if you need to look for aftermarket items instead, the Transmission Digest and Club3G sites suggests aftermarket is the go.

I'll leave all that for a later discussion as I'm not taking the box out, and of course you should be doing the wave spring too

Other parts required are the four seals at #42 on the exploded diagram and the three little o-rings shown just underneath (next to the 'N'). Actually six of those little o-rings are used throughout the box, but we only need three for the wave spring fix.

2 x MD760146 - SEAL RING,A/T CASE
2 x MD760147 - SEAL RING,A/T CASE
3 x MR486844 - O-RING,A/T CASE (old part number MD707200)

If you are a real tight arse you might not need to replace those if you are careful, but for probably only a few bucks you may as well since Mitsubishi recommend replacement.

And if you need a new sump plug washer you can get these from Repco etc but if you can't be stuffed hunting around the genuine part is MD000312 - GASKET,A/T CASE.

Disassembly procedure

Here is the section of the manual showing the disassembly procedure, from removing the rear cover to only as far as the wave spring.

The manual shows the transmission already removed from the car and sitting torque converter side down, but when doing the work with the gearbox still in the vehicle you'll be approaching from the side.

Because the torque converter side isn't touched, the input shaft will remain in place. It's not shown in these diagrams because the section before involves removing it. That's a bit of a bonus, because everything will be held together better and it should make re-assembly easier.

However when I attempt this job, I've also considered jacking up only the passenger side of the car, so that everything is at an angle and gravity helps all the components stay in place when slid back onto the input shaft.

(Taken from pages 58 to 61)

Steps 46, 47 and 48 of the disassembly procedure may differ depending on whether you have a pre or post facelift automatic due to the One Way Clutch (OWC) being added at some stage. Does anyone know when that occurred?

See this thread for more info:

http://ozvr4.com/forums/showthread.php?t=5110

If you have a pre-facelift (or non-OWC box) you may need to follow the steps above to remove the individual parts. Not really any drama.

However if you have a facelift (or OWC equipped box) then it will all be conveniently contained in one unit called the 'Planetary carrier assembly'.

Note: I see the original exploded diagram I posted above has already been updated to match the one below.

(Taken from pages 127 & 128)

This post was what got me thinking..

http://www.club3g.com/forum/problem...n-most-likely-dead-need-help.html#post2423187

But, no I haven't heard for certain of anyone doing it while the transmission was still in. But that's probably because nobody knew it was possible, and generally people don't bother about stuff like this while everything is working fine. Many people don't even know about the wave spring itself, just that our boxes are weak for some reason.