Harrison diff setup

[muzzza]

I have a Harrison car under construction. LS2 crate engine, T56 tremec with centre shift and R33 Skyline diff.

Engine and gearbox are positioned in the chassis. Axis angles down to rear at approx 1.5 degrees, which all looks OK.
Diff cradle is mounted in the usual way, but diff pinion angles down at almost -2 degrees..........instead of angling up towards gearbox axis.

The cradle or differential needs to be rolled up at the front to align more closely with my gearbox axis to avoid stressing driveshaft uni joints.

I would be interested to know of any other Harrison owners who have identified this problem with there cars

[WKB]

Originally Posted by muzzza

I have a Harrison car under construction. LS2 crate engine, T56 tremec with centre shift and R33 Skyline diff.

Engine and gearbox are positioned in the chassis. Axis angles down to rear at approx 1.5 degrees, which all looks OK.
Diff cradle is mounted in the usual way, but diff pinion angles down at almost -2 degrees..........instead of angling up towards gearbox axis.

The cradle or differential needs to be rolled up at the front to align more closely with my gearbox axis to avoid stressing driveshaft uni joints.

I would be interested to know of any other Harrison owners who have identified this problem with there cars

Muzzza,
I made up some large dia washers and used them to shim the rear cradle mounts to give the required pinion angle.

Warren

[Merv and Sharon]

Welcome Murray!!

Merv

[sambo]

Interesting. I've heard that you don't want universals to be perfectly square and mine aren't. What's the exact spec you need to follow with these cars?

[Krait]

Quick and dirty explanation of driveline phasing...

And another.

Cheers

[muzzza]

Thanks Merv..............Muz

[Merv and Sharon]

Murray is pretty knowledgable on this topic having built quite a few race cars and he is wanting to know how others have done it on the Harrison. I measured the angles with a digital gauge on the yoke of the unis and as long as the difference was less that 4 degrees I was happy. Maybe wrong?

[Rog246]

Hey Muzza, and welcome to Club Harrison !
You buy things the drifters call pineapples (maybe 'cause they're yellow!??!) which apparently allows you to change the angles of the rear cradle which in turn changes how the end behaves. their not real dear about $100 I think. I got a set for mine-just in case. I also bought a whole bunch of adjustable rear control arms which are very well made and gives you TOTAL rear camber, caster, toe and anything else you haven't thought of to adjust-worth the money by the looks of it.
Rog

[byroncobra]

Welcome to the Harrison stable Murray

I had the same problem with mine........i couldn't do much with the whole cradle angle as with my earlier built car, #38, there was clearance issues with it and the chassis. Incidently I removed the rubber/goop filled Nissan mounts and replaced them with Nolathane.

As Warren did, I bought new longer bolts and packed the front of the diff up with spacers to achieve around 3 degrees. I would have lifted the T56 a little but, once again, was confined by the clearance in the trans tunnel. After lots of fiddling with the dremmel I've only got a couple of mm gap

Greg

[muzzza]

Thanks for your responses and words of welcome Guys........Nice knowing there are others out there with the same " illness "

In the short time I have been building, I have met a lot of really helpful Guys.....has been great.

Dropping the rear of the cradle is an option........but as the cradle supports the inboard ends of all the suspension arms, it also effects camber curves, squat characteristics under hard acceleration, the rear roll centre and the roll axis of the entire car.

Target will be to get pinion and gearbox axes as close as possible to parallel with no more than about 15mm offset tbetween axes to ensure needle rollers in uni joints get enough movement to lubricate properly.

May look at raising front of cradle a little and rolling diff head up within the cradle. (rubber cradle mounts will need attention by all accounts - especially without snubbers that have been removed )

The current set-up (16" AVO coilovers - 300lb springs )
has the halfshafts sitting almost straight at full "Droop " ( no load )

Would be interested to know how much preload you Guys are running on your coilovers and roughly how much droop.
( in other words - a rough idea of how far the car compresses the rear suspension to arrive at normal ride height ) and does the car sit OK at this height ? ( 17 inch rims )

PS trying to get as much info as possible at this stage.......so with this build it all works first time !! ( should have / would have / if I was doing it again etc )

Thanks..........Murray

[WKB]

Originally Posted by muzzza

May look at raising front of cradle a little and rolling diff head up within the cradle. (rubber cradle mounts will need attention by all accounts - especially without snubbers that have been removed )

Murray,
Your mention of raising the front of the diff made a few more brain cells work and I remembered how I did get the required diff angle.
On the cradle bushes, I cut the steel tubing through the bush level with both sides of the cradle arms. The large washers I made did two things, 1, they clamped the cradle to chassis which reduced the effect of the rubber bushes to almost nothing and 2, I could use this large washer as a shim.
On the diff I replaced the rubber bushes in the front of it with a round piece of steel that was flush with both sides of the flange. Again I used large fabricated washers underneath of the flange to bolt the diff. The top of the flange bolted flush to the cradle. With the new position the diff I just fine tuned with with different thickness fabricated washers under the rear cradle bolts.

The diff rubbers were replaced on a recomendation of the company that did tailshaft. They said they have seen these rubbers ripped out on acceleration with high horsepower cars. As you are using a chev motor that might not be an issue.
The secondary side effect was I could change the diff angle.

[muzzza]

Thanks Warren,

Seems anything that minimises movement of the cradle is not all bad.

Subframe on rubber bushes is a great idea for crusin'..........but a bit short of ideal for a car leaning towards a race car.

I appreciate your note re " Chev motor "........I only used it as it was left over from a previous project...........perhaps I should save up for a "Ford "

Appreciate your input Warren.

Regards Murray

[Rebel1]

Originally Posted by muzzza

Target will be to get pinion and gearbox axes as close as possible to parallel with no more than about 15mm offset tbetween axes to ensure needle rollers in uni joints get enough movement to lubricate properly.

Thanks..........Murray

Is the engine in the Harrison moved a little to the right or is it on the chassis center line?.

[muzzza]

Had a quick measure...........and egine is about 10mm closer to left ( passenger side ) of car.

Murray

[Rebel1]

Originally Posted by muzzza

Had a quick measure...........and egine is about 10mm closer to left ( passenger side ) of car.
Murray

That's interesting Murray, must be for header clearance ?.

Given our short tailshafts I would have expected it to be moved to the right to minimize the diff pinion offset.

I'm guessing a pinion center offset of maybe 40mm so a 10mm left engine position increases that to 50mm between gearbox output and diff pinion .

[Merv and Sharon]

It is certainly not ideal Lea and Murrays work will help others. Also your idea about the front bush is great Warren. Wi be doing that on Sunday!

[sambo]

I've been testing my Harrison the last few weeks and there are a few squeaks coming from the R33 rear suspension (not reconditioned) as well as noticeable squirm under moderate power and when transferring weight or going over undulations in the road. Rather than start a new thread I thought I'd add some info here.

Taken from an eBay listing, "The stock Nissan rear subframe bushes contain silicon-filled Rubber Bushes. Even on stock HP GTS-T's, the stress of putting the power down twists the rear subframe- punishing the subframe bushes. The rubber perishes and the silicon leaks out- this leaves an air filled void that can lead to vague handling and a loud knocking from the rear on really bad examples".

So given that this is a 15 year old cradle, I'm going to source some poly bushes from eBay. A UK seller has "85 shore A" duron bushes with alum inserts and steel washers delivered for about $80 AUD. More info on duron ratings below.

Shore (Durometer) hardness test [SubsTech]

Next stop are the upright and control arm bushes, pictured below. Two lower control arm bushes per side (green dots) and 4 upright/control arm bushes per side (red dots). Roughly $15 a piece.



Interesting info from Whiteline below on ways to "shim" the rear cradle for desired road holding behaviour.

http://www.whiteline.com.au/instruction/203a_KCA349.pdf

I plan to make these changes in a few weeks once I'm through engineering, will post my findings after that.

[byroncobra]

I replaced my Nissan bushes, one of which was already leaking silicone with Nolathane bushes:

Nolathane

Also added Whiteline adjustable upper control arms allowing alot more adjustment than the std cam adjustment. I needed these to get the camber correct.

[byroncobra]

BTW getting out the old bushes out is a mongrel job.....after trying to belt them out unsuccesfully I took to them with oxy and burnt them out

[Merv and Sharon]

Paul, Greg did you also do, or plan to do, the rear sub-frame cradle bushes? Not sure if this is the correct pic (at the bottom of the page): Option 1 Garage - performance car japanese performance parts Brisbane Queensland Australia workshop drift racing nissan

Any advice re the best sources for the other bushes?