Linish 3rd gear syncro or get a new syncro and hub slider?

[milkandoj]

I'm giving my switchable CP5OH gearbox a freshen up (similar to a W5M33) after snapping an Al selector fork. May also do a 4 spider center diff conversion.

Third was getting crunchy, I was going to order a new 3rd syncro and hub slider from Jacks or Shep transmissions in the US, however a local gearbox place says they can Linish the syncro to improve it. May as well let him have a go at 2nd to freshen it up but its not too bad.

Does this actually improve it for a decent amount of time or is it worth the extra cost and wait for me to get the 3rd syncro and hub slider?

Can anyone say for sure that there are inherent weaknesses in a CP5OH box compared to a W5M33, pulling them apart they look pretty much the same to me.

 

[brisvr4]

Use a hub and slider from a w5m33 box Gerard. The C50 boxes have a different internal structure ( 3 legs rather than solid ).
I'd just put in a new syncro.

 

[EVO-00X]

Get a new synchro, chances are the one in it now is damaged anyway.
Linishing or polishing the synchro is least important. Its more important to have good oil, a good condition synchro and good synchro to hub slider tooth engagement. If the hub slider has chipped teeth then there's nothing a new synchro or polishing can do to make the problem any better. I say you were on the right track in the first place and get the new 3rd synchro and hub slider, plus a new 2nd gear synchro. Dont forget to get 3 new keys and 2 new springs for 1st/2nd, and 3 new keys and 2 new springs for 3rd/4th.
Also note that 3rd gear synchro is on the input shaft and the 2nd gear synchro is on the intermediate shaft. Just be aware of this as you will have to pull the bearings and sleeves off both sticks to do it.
Cant help you much with the gearbox but if they are similar to normal VR4 internals they inherently have weak first gears and alloy shifter forks.

 

[blackvr]

I see a bit of variation in the range of VR4 gearboxes regarding synchros. Some have for 2nd and 3rd gear, cloth/paper lined synchro rings, others are brass. Given that there are no chipped/worn teeth on the gear and worn sliders etc, I have had a fair bit of success in deglazing the cone surface by grit blasting , and lapping in replacement full brass synchro rings in. Thats the problem... people in the past have used crap oil and simply glazed the cone... which leads to chipping and wear from trying to bang it into a lazy synchro. Ditch the cloth lined synchros, as they are prone to heavy wear with hard shifting and you cant lap them in without tearing up the cloth/paper like insert .

I also have a switchable box in parts if any one needs bits out of it.

Cheers Mike

 

[to4garret]

The C50 boxes have a different internal structure ( 3 legs rather than solid ).

could you expand on this please?

legs of what? the casing?

 

[milkandoj]

could you expand on this please?

legs of what? the casing?

+1 I'm trying to figure out what the difference are or where the weaknesses are compared to a W5M33 box that may be easily improved on while the box is apart.
Of if it cant be improved on and will be weaker than a W5m box anyway, so ill expect it to blow up quicker and probably not over invest on parts in it.

Thanks for the info and parts list guys!

 

[brisvr4]

I've pulled apart a couple of C50 boxes, imagine that you are looking at the hub like a dinner plate. On the C50 boxes there are 3 seperate arms which connect the outer section with the inner spline that slides down over the input shaft.
This is a weakness they seem to have addressed in the later boxes. I swapped in a hub and slider from a w5m33 box both times with no issues whatsoever.
I'll see if I have the old broken bits still.

 

[milkandoj]

Thank Tim, well ill get the new hub and slider and sort that out then.
I'm almost tempted to weld the center diff lol but its a street car so ill go the 4 spider center instead.

 

[milkandoj]

Is stripping first gear common in a W5m33? I though they normally stripped 3rd or 4th from torque, and Aluminum selector forks from ham fisted shifts into 3rd.

 

[brisvr4]

The vr4 1st gear is the weakest of all the mitsi 1st's.
I've stripped 2 of them previously so I swapped to a dsm 1st gear and input shaft. Haven't had an issue since.
It is a shorter ratio though, 3.08.
There is also the evo3 input and 1st gear but it has a longer ratio than the vr4 1st.
If it's apart now I would change it myself.
I've also had no issues with 3rd or 4th since I set the preloads correctly for my power.

 

[milkandoj]

So id need a dsm input shaft to switch over to a dsm first gear? The have a lower ratio correct. I swear i seen a few of the American guys were putting vr4 first gears in their box's due to the longer ratio.
Whats weak about the vr4 gear, the metallurgy or is it because the gear is longer and therefore more load when launching.

Im still a bit unsure if to build the CP5OH box, unless i know for sure im addressing the weaknesses, if it was a W5M33 id have no problem at throwing some nice parts in it as their weaknesses are more well documented.

 

[brisvr4]

Yes you will need both the input shaft and 1st gear Gerard as it does have a different ratio for 1st.

This is from Jacks website commenting on our 1st gears.

GVR4 1st Gear = Weak
The Galant VR4 first gear is an option many people want. The gear is taller than OEM giving you a first that is not totally useless. The GSX first feels very short, and with so many people using large turbos, a taller gear is a nice thing to have. We carry the GVR4 first gear in stock and can install it for you at an additional charge of $220 in any of our builds (all years). We do not guarantee this gear though. They are weaker than the OEM GSX first and if you are using a heavy clutch or are over 400hp, this gear can break. We do not recommend this gear, but will install it if requested. The pic below is of a broken unit out of my own car. My car had a solid center diff at the time and it only took 7 good launches to break it. I was very disappointed, because it was really nice before it broke.