STI Six-speed DCCD 2WD Conversion Issue

[longislandwrx]

yeah those possum pieces are nice but $800 usd iirc.

[fryguy]

yeah those possum pieces are nice but $800 usd iirc.

Do you know of anyone that used these for a 2004/5 STI 6-speed?

[fryguy]

So I ordered this center locking diff spool from Possum Bourne. It ended up costing about $1K with shipping. I'll update this thread once I get it.

[Zach34]

Jeff, I'm using a 2005 STI donor. I just started the 6-speed FWD conversion and of course ran into the exact same issue you posted about. My trans has the oil pump driven by the center diff and the parts look precisely like the pictures you posted.

I can't understand the price for that Possum kit.

A few thoughts:

-There are two concentric splined shafts, that either drive or are driven by the center diff. I'll call the large hollow splined shaft the "outer" shaft/splines and I guess they seem to drive the center diff (could be wrong). The "inner" shaft/splines are threaded through the outer shaft/splines and drive the rear wheels? The outer splines drive the flange of the center diff that contains the oil pump drive gear.

-It seems that the only purpose of the adapter flange supplied in the kit is to lock the "outer" splines to the "inner" splines. Is this correct? What does the inner shaft drive apart from the rear wheels that would necessitate it being locked to the outer splines?

If my thinking is right, it seems like the adapter flange could just be welded to our oil pump drive flange. Some measurements will have to be taken to make sure the adapter flange isn't too short or too long. Could this work?

If not, where did FFR source their adapter flanges? I'm guessing these things have to be hardened.

I don't want to drop $1k on this...

[fryguy]

Yes, that was exactly what I was initially thinking: weld to the drive flange and figure out the correct length of the adapter. After FFR confirmed that the adapter was not going work, I asked what was the purpose of the adapter. Was it there to just hold the drive flange on? And does the other end of the adapter need to butt up against the tail housing to hold it on? I have not received a response yet on that. The problem is that I don't feel comfortable welding the adapter to the flange and trying to figure out the correct length. I don't want to risk damaging the transmission. I already ordered the Possum kit. I don't mind taking measurements for you or anything else if you want to attempt your own solution.

FFR didn't reveal who their supplier was to me. But it appeared that they were relying on the supplier for answers and they weren't responsive.

[Zach34]

OK, I talked to Tony at FFR today. He suggested that he may have heard of somebody welding the adapter on one of these center diffs. Most importantly, he confirmed what I suspected, after looking at the diff and some diagrams: The purpose of the conversion kit is to lock the "driven" shaft of the transmission to the "pinion" shaft for the front differential. The attached diagram shows what I'm talking about and should make it pretty clear. The center diff is normally driven by the shaft labelled #8. The front differential pinion gear is part #1. Since we don't have to split power between the front and rear wheels anymore, all we need to do is lock those two shafts together. That's what the adapter does.

I think I may have figured out a solution using the FFR 6MT kit. Instead of writing a dissertation, here's a shoddy video I hastily shot explaining what I have in mind. I sent a link to Tony, and I'm waiting to hear from him to confirm that I'm on the right track.

http://youtu.be/MfcI_CB_XN0

I have some reservations about welding it, but I think I'm going to attempt it. More to follow on that...