Rb20det Gearbox Q's/problem's

[DRFTD_32]

Ok after racking both my brain and a few of my mates I have finally come to a point where I have no idea where to go from to fix my gearbox problem...

I first got my car from Japan with a farely rough gearbox, I could not straight away change gears, I would need to shift slowly (let the gear disengauge and then change) it also felt like it needed to have the bearings done...

After looking around for a while a bought another RB20DET box and a new Exedy HD clutch kit.

After installing the new box and clutch it became impossible to put it into gear. Even after bleeding the clutch it still wouldnt pull far enough out that it would go into gear.

Next I decided to change the clutch slave cylinder. After buying a new cylinder and installing it when we went to bleed the clutch again I found that the slave cylinder was going past its max point of travel and shooting the lug out of the slave cylinder.

With my car now stuck in the middle of my mates workshop we turned back to the original slave cylinder, I figured that it was not pushing the pinion all/far enough out so I got a hardened steel rod and mad a longer pin to go in the end of the slave cylinder, re-bled the clutch and it worked really well!

After a week or two of driving it has returned to a similar or worse point then it was before.

Now if I jump straight onto the clutch very quickly or try a to double clutch and side step the clutch it makes a loud grinding noise and it seems like it is stuck between gears, the car then needs to be turned of then back on again to resolve it.

Anyway if you have had this problem or have any ideas please let me know!

Thanks Heaps!

[T04GTR]

cool. it sounds like the clutch is not bled properly. or the slave rod isnt long enough.

by that i mean the long gay loopy tube thing that the lines go through. if you can piss the whole thing of just re-position the thin pipe from the master cyl to the slave cyl hose bracket.

also with a new clutch installed the slave cyl rod should only have a about 4mm left till it bottoms out in the cylinder. if you can put the rod on the fork with the slave still bolted up the rod is to short.

just make another one out of a m8 bolt and round the ends on a grinder etc.

hope that helps.

[blind_elk]

Have you checked the pedal height? The pushrod from the pedal to the master cylinder is threaded and you can adjust the free height of the pedal to maximise the performance of the hydraulics.

[Mitchee]

Hi Guys, im a mate of DRFTD's and ive had a couple of goes at fixing his beast.

The adjustment at the pedal is maxed out, ie he is getting as much travel out of the pedal as possible because the attachment on the master cylinder pushrod is all the way out.

Ive bled the clutch with him numerous times, the one thing I HAVE noticed is that the fluid coming out of the slave cylinder is darker than the fluid in the master cylinder. Ive put this down to being a dirty slave or master cylinder. This was actually what i was going to suggest to DRFTD next, a full removal of the entire hydraulic clutch system and a thorough cleaning of everything. Its possible there could be 15 years of shit in there that just doesnt wanna go away via bleeding it.

In regards to the box 'crunching', a quick dump of the clutch at stand still sometimes results in a harsh grinding noise, almost as if the box is popping out of gear from the stress and because the lever is still in gear, pushing the mesh together and grinding them up.

Changing gear consists of DRFTD clutching in, pushing the gear lever into the gear he wants, and waiting for it to slot in.. This suggests to me syncros, or a clutch thats not disengaging 100%... im leaning towards the clutch because of what ive said above, and the while turning the car off business (zero input shaft speed).

So you guys think I am on the right track?

Edited September 21, 2005 by Mitch_Rona

[paul74]

Hey what you should do is get rid of your rb20det box and get a rb25 box only have to get your tail shaft shorten by 150ml and make a braket for under the floor for the mount an a longer cable for your speedo. Rb20box is too small cant handle much power and when you go puting in a heavy duty clutch you will distroy your gear box. rb25det gear box is good for 600hp standard rb20 300hp if that

[NateR31]

Hey what you should do is get rid of your rb20det box and get a rb25 box only have to get your tail shaft shorten by 150ml and make a braket for under the floor for the mount an a longer cable for your speedo. Rb20box is too small cant handle much power and when you go puting in a heavy duty clutch you will distroy your gear box.  rb25det gear box is good for 600hp standard rb20 300hp if that

<{POST_SNAPBACK}>

thanks, im sure he didnt know that

[DRFTD_32]

Anyway incase any one was interested or has a similar problem it turned out that it was the Spigette Bearing it had been totally destroyed.

I have some more info if anyone wants just let me know and ill post it for you!

Thanks for your thoughts!