Nissan Skyline r33 gts rear end conversion into my VL!


  What Iím doing with my rear end is a little different. Instead of the usual spool or 9" conversion, Iím going to fit an r33 gts skyline rear k-frame complete. Thatís IRS, viscus LSD, 4.11:1 gears, large vented brakes with twin piston callipers and it's the correct width too. Also Iíve never heard of these things braking, even in a 9sec car, so they are strong! Other advantages are adjustable camber and tow, much lighter unsprung weight, coil over struts and rear wheel steering not that it will be used...
At the jap importers I picked up this rear end from, they had a z32 300zx K-frame lying around also, it has a wider track but the suspension arms and uprights are the same as the skyline, the only difference being the 300zx has aluminium uprights and the skyline has cast uprights (and different shocker mounts). My thinking was the alloy one's have to be lighter so after a little chat to the boss I started to swap them over! After mucking around for ages and removing the seized axles from the hubs I finally managed to get them all pulled down. The weight difference is 2kg, with the cast one's weighing 5.3kgs and the alloy one's weighing 3.3kgs, Worth the effort! I wish I could have used the entire 300zx rear end as it is a gorilla, bigger center, bigger CV's, axles and splines!
To mount all this to the bottom of a VL shouldn't be too difficult with the frame mounting on 4 pins which line up ok with the chassis rails! It's just a matter of welding these in the right place with appropriate gusseting and bracketing. The shocker towers also require a fair amount of modification but line up too!
I will detail the installation on here when I get up to doing it! So far I have spoken to an engineer about the roadworthiness of this, it's all good! And a race suspension shop about rear coilovers to suit, no probs there either!

 

 

25/5/03

I've finally got around to start fitting the r33 gts skyline IRS k-frame to my VL!
Here's a couple of pics of the k-frame jacked up roughly in position but 75mm lower. I have to cut out the rear jacking points for it to fit in the correct position, but thatís all! I almost can't believe how well everything lines up!
All the old suspension brackets will be removed but first I am going to build a rotisserie to turn the whole car up side down to make it easier weld and work on. Should be fun ;)

 

 

4/6/03

Another weeks work and the car is up-side-down ready to be hacked into!
Here's a few pics of the rotisserie mounts onto the car and the stands as well as the engine crane Iíve always been going to build, I needed it to lift the car up high enough so it got built!

After the vl was on the stands and swinging free, I tried to turn it over but could only manage to get it to about 90deg by myself, which means I made the pivot points too high...
The easiest solution was to remove the front cross member as this would lighten the bottom of the car and put less strain on the mounts. After removal I could turn it over quite easily by myself, then after securing it upside down I went for a walk around on the bottom of my car! It's very stable as it would want to be!

 

 

16/6/03

OK, all the old suspension mounts are gone so there's no turning back now!
With the IRS sitting on top and easy to move I could go over it with tape measure to find the correct position, taking into account ground clearance, wheel position and suspension arm angles I found I needed to trim a little off the rear cross rail for the back to sit in far enough. It can be fitted to give the correct arm angles at a lower ride height, but only just! The front upper control arms come very close to the chassis rails as shown.
The strut towers need to be moved forward about 50mm but there's plenty of room for this too! I'll most likely get r32 gtr rear struts as they are about the right height and have the right ends on them.
I borrowed a supra wheel from my local jap wreckers that is the same size (16x8, 225/50R16) and has the same offset as my wheels but fits the nissan stud pattern, so I could check the wheels travel in and out of the wheel arch, it's perfect, plenty of room and travel! I could even fit a slightly wider tyre without any problems!
By the end of this week I should have most of the mounts done!

Note: The pics have been rotated.

 

 

25/6/03

Here's a rough start to the mounting pins, a lot needs to be added to these of corse, but the positions and heights are correct! When trying to work to the nearest mm, I quickly found out things don't line up... The chassis rails and k-frame are a few mm different from side to side which made it a real pain to get it right. I had to ignore a few measurements and just work off points on k-frame to the end of the sills. The hubs ended up in the right place so thatís all that matters!
You can see the bits I cut out of the rear cross rail to sit the k-frame in the body far enough.

The pics are the mounting pins for the k-frame in there respective positions, top left pic is the front left pin, bottom right is the rear right pin. I have marked yellow outlines where extra plates will be welded in.
And the shocks are Koni sports adjustable damper with adjustable height to suit a r32 gtr skyline, thanks to Darryl at Australian Auto Solutions for selecting these! They worked out to be perfect length as it keeps the spring above the top arm and the strut tower short. They allow for 90mm of bump and 60mm of droop.
The pins are 7/8" high tensile bolts turned down to a 21mm shank with a m12 thread.

 

 

2/7/03

With the mounting pins tacked in position (got to get a mate to weld them up properly) I started on the shocker towers! I'm using some 4.5" exhaust tube with a 3mm plate welded to the top. Next I cut out the old shocker towers and trimmed the inner guard forward. Now I positioned a compressed shock with the new tower fitted to it, into the hole Iíd made and tack welded the tower in with the suspension also fully compressed to get the right tower height. I found I needed to trim the edge of the chassis rail for the shock to clear the wheel, then I found the angle of the shock onto the upright became tight in the fully compressed position. Moving the shock further forward fixed this but then the shock came too close to the upper arm... A compromise was found eventually that made shock clearance great at ride height but closes up at the extents.
If I had kept the r33 cast iron uprights (instead of the alloy 300zx ones) I wouldn't have had any of these problems as the shocker mounts in a different way...

The pics show the distance between the top arm and shock when fully compressed and extended. And the angle for the upright to the shock. You can see how the upright rolls forward when compressed. I believe this is to compensate for the weight of the car trying to roll it backwards, so it shouldn't be so bad with the weight on it!

 

 

18/7/03

The first pic shows one of the front mounting plates from underneath. You can see the bolt head with gusseting to the top plate. The middle pics is the rear left mount underneath, showing the gusseting.
And a shot of the left hand shocker tower from below (above up-side-down). You can see how I have trimmed the edge of the chassis rail back to the vertical to allow enough room for the spring when the wheel is fitted.
I have tacked the shocker towers in the correct position as well as the all the mounts are permanently tacked in ready to be welded so basically it's just a matter of making up the rest of the plates to strengthen and fill in any holes and welding it all up properly and it'll be finished! :D

I have also removed the hubs and taken them to the engineers to have the stud pattern changed. He said he will fill the stud holes by bronzing and then re-drill them in a mill, MIGing the holes up doesn't work as it makes hard and soft metal that is impossible to re-drill in the right spot...

Next on the to do list is making the strut and spring tops, as I now have the expensive spherical bushes to make cups for!

 

 

29/7/03

Now I have made up all the strut top pieces, the top plates, bearing cups, top and bottom bearing bushes and top spring seats, as you can see them laid out and assembled. It's a lot of effort to do away with the rubber bushes but a must for track work! I'm fairly lucky to have a lathe at home!

I also have the hubs back form the engineers with the stud pattern changed! It's still not quite perfect but some studs are only a fraction of a mm out so the wheels still fit fine. They ended up drilling out the holes and MIGing them up as they are made from cast steel, not iron, before facing the front and rear and re-drilling. They did bronze the plugged hole in the cast iron rotors and redrilled them in-between the original holes.

Left to do now are locators for the springs. The bottom spring seat adjuster nuts have 57mm locators where the spring i.d. is 60mm... also the spring o.d. is around 83mm and the seat is 78mm... This is pretty dodgy but it's what koni use for 60mm springs??? It's easily fixed by a new locator/seat, basically a bush to sit on the nut!
And locators for the top seat that will just slip on the shocker shaft!
Then locators for the wheels as the hub centres are 66mm and the wheel centres are 70mm, just need to make a ring with a 2mm wall. Thatís about the conversion complete! Just a matter of finishing off the mounts!

 

  3/9/03

OK, here it is all welded up! Now I just have to clean it up (a lot), coat the bottom in a thin layer of tar and repaint the boot inside...
The top left pic is my mate Steve doing the finishing touches! Bottom left is the new strut towers in the boot. The 4 in the top left are the mounting points in there respective locations. And the 2 as the bottom are the strut towers left and right.
It's getting exciting, but Iíve still got so much to do... it'll be at least a month before I have any results.

 

  16/10/03

I've been pretty slack updating this, but I haven't been slack on my car!!!
The rear end mounting is all finished, painted (mat black) and all bolted up. The car is back on the ground and rolling. I have dropped in a stocky engine and Iím just working on the minor details, brake lines, tail shaft, fuel tank, ect. Another 2 weeks and it should be ready to take for a spin!!!

 

  2/11/03

It's finished!!!

Well enough to drive and race it!

With a fun day at my nearest race track (Winton motor raceway) approaching at short notice I really had to put in some hours get the rear end and brakes completed, but it was all worth it! With the VL only ready to go late saturday night before the fun day on sunday, I was lucky nothing went wrong.

So here is some results of the conversion,
Ride is improved but not greatly, still rough but not as harsh over larger bumps. Softer springs would help!
General handling feels more responsive but that may be just because Iím used to my pulsar...
Hard cornering resulted in massive oversteer even with the stock non turbo engine but very controllable with no tank slapping! On the track this was very fun but not very fast. Checking the rear toe found the problem having 4mm of toe in (difference in width from front to rear of the rear tyres), I adjusted it to 2mm of toe out. That made the rear stick to the track like glue and I found it very hard to drift around corners after that as the front understeers all the way around...
Being a 'fun day' the tracks lap timers werenít running but the stop watch was! Clocking a best time of 1:57 with traffic was good considering I am down 120hp without the turbo engine when I did a 1:52 late last year.

Overall Iím extremely happy with the conversion with the only thing Iím a little disappointed with being the viscus LSD slipping a lot, and I think softer springs would help but Iíll wait until I get the front to grip before changing spring rates. I have plenty of adjustment to play with in the mean time ;)

Heaps of pics to come of the rest of the little mods needed to make it all go and fit!

 

 

 

 

 

 

 

4/12/03

Here's most of the finishing touches!
To fit the tail shaft was easy, just removed the flange off the diff and had the locating center machined out and 4 new holes drilled to suit the standard VLt tail shaft.
And the center bearing mounting bracket required the bolt holes slotting as the diff is about 5mm forward of the old diff. The yoke just sits in the gearbox 5mm further, no problem!

The fuel tank was a little more difficult with the front of the tank in the way of the rear steering rack and motor. I could have removed the rack and made a bar to replace it but I think that would have been more difficult than modifying the fuel tank plus I want to have a play around with the rear steering one day! So I cut the front off the tank and welded a new plate in but I shifted the fuel sender the wrong way so it sits directly behind the rack gearing... It clears by about 3mm... Plans are to make an aluminium tank!

I am still yet to hook up the hand brake and finish off the brake line mounting.

 

  25/03/04

Hand brake is hooked up and works but it's not perfect and need changing, cable almost touches the tail shaft.... The lever ratio on the handle is too great, meaning it pulls all the way up before working and is fairly light.

 

  29/05/04

I've made up a new fuel tank to clear the rear steering rack. I got hold of another tank and cut the front off. I had to move the swirl pot back and to the drivers side a little so the sender would still sit inside. Pretty simple, just time consuming to fix all the leaks ect. Fits well!