RB25 tranny and driveshaft Issue - Please help!!

[judasentinel]

Today, Ray (BigBlueR32), Mike (belontay_typeM) and I worked on swapping my tranny. I was running an RB20 tranny with the RB25DET with fracked syncros. The decision was to put in an RB25 tranny in. I also had an RB25 yoke and a complete RB25 driveshaft (both pieces), but after we took the RB20 tranny and driveshaft out, we found that the RB25 driveshaft is longer than the RB20, and that the front half of the RB20 driveshaft is wayyyy smaller.

We thought of just loosening the front u joints of both driveshafts and just sliding the RB25 yoke on the RB20 driveshaft, but the holes on it that hold the yoke in are too small to hold the RB25 yoke.

So the issue came to deciding what can be done. And I am stumped.....completely. I have been told that I need to get the RB25 yoke welded to the RB20 driveshaft, but I'm not sure at what position I should make the cut on it to weld the yoke. Has anyone done this? Is there a way to measure it? Is there ANY way to make the RB25 driveshaft work? Or can I get a one-piece used driveshaft from another car to work?

Would really help if someone could help me with this. My friends who came to help me (and I thank them with all my heart - they went out fo their way for me once again!! You guys are awesome....MAD PROPS TO YOU) told me what to do (RB25 yoke on the RB20 shaft), but the confusion is the exact length to cut the driveshaft at so I can weld the RB25 yoke on to it.

Thanks.

[linedriver]

i think you gotta take an inch off the driveshaft or something like that. pretty much just get under the car and measure out the length needed and then cut away. once you get that done, you should take it to a shop that handles driveshafts and get them to balance it for you so you dont run into odd vibrations.

[judasentinel]

Yeah I figured that, but HOW do I confirm the exact spot to cut it? The thing is that I'll only get ONE chance to do it. And if its cut too short or too long, I'm toast. Do you think I can use the RB25 driveshaft at all? Its hanger bearing is a bit loose and it doesnt have a bracket in it to hold it in place. Any way to do that, or is a cut and weld the ONLY way?

I wish I somehow could measure the right spot to cut. Don't wanna make an error there, you know..........

[linedriver]

measure twice, cut once, i was always told that at work. since you only have 1 shot at this, i suggest you cut a little bit off at a time and tack it together and then test fit it. if its too long, then cut it down some more and retack and refit it. eventually you will get it to the right size. might seem like a pain in the ass, but its not as bad as one might think. worst case, you can always get a custom made drive shaft, but there might be alot more downtime then expected

[judasentinel]

Update:

I finally found a driveshaft place in Scarborough that was willing to put my RB25 yoke on the RB20 driveshaft. But they are charging around $150 (tax included) for this. I tried to measure the exact point at which to make the cut on the RB20 driveshaft, but couldnt figure it out because the shaft would sag right in the middle (from the hanger bearing point). It seems that the RB20 shaft is a bit short for the RB25 tranny (since the RB25 tranny is a bit shorter than the RB20 tranny - around 1 cm). So I had to ask the guy to make the new driveshaft at least as long as the RB20 one. I also learned that there is always a bit of a play kept inside the tailshaft of the tranny, so that when the car hits a bump or a corner, the driveshaft moves front or back......and so you need a bit of space inside the tranny for the yoke to move.

I'm just hoping that when I pick it up tomorrow, it would fit right in. And in case the driveshaft ends up being a bit short, is it possible to use a spacer somewhere along the shaft to lengthen it?

[BigBlueR32]

the tranny's are the same length man we checked it out the reason the RB25 looks shorter is because the dust sheild was off..:-P

[judasentinel]

Ray, I spoke with Mike today. Are you still up for some HD style Gran Turismo tomorrow? Beer's on me, and so is the dinner, lol.....

....I think so too that the driveshafts are same length. Skyline Australia people think that there is a difference of around 10 mm (1 cm), so I just hope that everything lines up. Im hoping to get the driveshaft tomorrow afternoon. We can finish it off and then I will kick everyone's butt in GT, OR we can play Oblivion or Formula One.......it will be fun.

[judasentinel]

Driveshaft issue resolved (I hope). Got a custom shaft made from RB20 and RB25 shafts. You need to have it as the same length as the RB20 one, but the yoke is from the RB25 and so is the U joint surrounding it.

Thanks guys....

[jeff]

any pics this will help us all thanks..

[judasentinel]

I did a write-up on the whole process that we followed in this section. I took some pics, and will try to upload them soon. As it is, the driveshaft for neither the RB20, nor that for the RB25 will work. You have to combine the two to make a new one to make it work. From the RB25 driveshaft, you need the yoke, the front U joints, and around 1-2 inches of the pipe behind it. Then you have to get the RB20 driveshaft cut from the front to weld the part of RB25 driveshaft that you got to it and then balance the shaft again.