Can some transmission experts look at this?

[cheekychimp]

This is a fairly simple question but I have had so many conflicting answers recently, that it has started to do my head in and I now don't know if I am barking up completely the wrong tree.

I have a complete 3.909 ratio transmission with correct rear differential (out of an Evo/RS GVR4) that I want to freshen up and throw in my daily.

Basic idea was simply to get one of the transmission shops to do me a straight cluster with EVO III gears and have the double synchro mods done.

Then I get told I can't run the EVO III gears in the EVO/RS box and need to use the EVO III front ring and pinion. I don't think this is correct. It will work, but in order to make it work I'm pretty sure I would then require the EVO III transfer case to get the correct ratio to match the 3.909 rear due to the EVO III front ring and pinion having one tooth less (or more?).

Everything I have seen so far suggests that the EVO/RS GVR4, EVO I and EVO II had exactly the same front ring and pinion and use a transfer case that is identical in ratio to any 1G DSM or GVR4. There are some minor differences in the individual gear ratios between the VR4 and the first two EVOs but other than that everything seems to be interchangeable.

EVO III gearsets seem to be the strongest available however and it just makes sense to get a full cluster with the synchro work done and get the box put back together over here using the original EVO/RS GVR4 front ring and pinion.

Am I missing anything here?

 

[brisvr4]

Paul if you want to use the Evo III gearset then you will also need to get an EVO III centre diff as the gears are cut on a slightly different angle.
You can use your RS ring and pinion as well with no problems.

Troy ( Mexican restaurant dude ) is running a 3.5 ring and pinion in his EVO III box. You just have to make sure that you use the RS Output gear with the RS ring gear and you will have no problems using your existing transfer case.

If you decide to use the EVO III ring and pinion then you will have to source an EVO III transfer case as they have a different tooth count on the ring gear.

 

[cheekychimp]

Tim thanks mate! Shouldn't be an issue getting an EVO III diff. I actually really want to try out the Cusco Tarmac EVO III diff but it's $$$$!

You raise an interesting point however. I have an EVO III Cusco Plate Centre Diff in my other car, but that car doesn't have a full EVO III gearset. Is that likely to cause me any issues?

 

[curtis]

Paul not sure on this because the chances of finding early evo parts in the states are super rare and I've never seen the two side by side but if you have a VR4 shaft that the evo III center diff is riding on it could cause problems. Its like a ring and pinion out of any other car in the world. If you try and change just one and don't keep them as a matching set you can have future problems, due to the wear pattern and how it was set up originally and how its set up now. I've seen it done and last forever and I've also seen it done and not last 15 minutes.


My buddy wrecked a mustang notch one time. Being stupid stopped and launched on a bridge and as he hit 3rd the car broke loose and went hard left as he came back on pavement from concrete and nosed into a ditch and hit a bolder sticking out the side of the bank. We pulled the entire rear end and put it in another car because it had just been set up with new ring and pinion, big axles and an auburn diff about a month earlier. We never figured out why but about 3 days later it exploded and before it happened it only made noise for about 20 minutes. Only thing we could figure out was the sudden stoppage that happened either twisted or bent forward on of the axle tubes or the g load dented a bearing. /ubbthreads/images/graemlins/dunno.gif We tried to measure and check everything but couldn't tell it was bent, maybe one degree out if anything. Now since the evo III diff has been in the car and you haven't heard anything might want to check to see if you have signs of metal wear on the drain plug magnet but I'd say its probably going to be ok.

Something else you can do is run by a parts store and get one of those sintered bronze fuel filters. Looks like a bunch of bronze compacted together into a tube shape. Find a funnel and cram the tube filter on the end then cap the bottom of it and filter all the trans fluid. I know it sounds anal but every 3 oil changes on the car I always filtered the trans fluid and put it back in. (warning this takes about all day). Metal particles in suspension is what kills a transmission and for piece of mind I use to do it. Probably didn't help but in my head seems like it did. /ubbthreads/images/graemlins/grin.gif

 

[cheekychimp]

Thanks Curtis,

Sounds like I may need to look at this but TRE put everything together and I would hope Jon has forgotten more about this than I'll ever know. It must be possible to do this because 90% of the aftermarket diffs out there are for EVO III cars and not VR4 specific.

As for the filtering thing, I have actually been considering running a transmission cooler for some time not only for the cooling but because I could run a filter inline and have it filtering 24/7.

 

[brisvr4]

Curtis, that is why I suggested Paul should run a matched pair ( output gear and crown wheel ) The centre diff slides down on to the output gear and as there is no actual meshing of teeth between them there shouldn't be a problem as long as the connection is straight.
I case I have described it differently because I'm on the bottom of the planet here's a picture ( disregard the mess in the bottom of the box ) /ubbthreads/images/graemlins/rofl.gif

 

having finished my 4th 1g trans and just using a evo gear set and double cones in concur..