VR Senator with LSx454

[VRSenator065Participant Adelaide SAVR Senator LSx454 1960 Kombi (project) 1921 Nash Hot Rod (future project) View build HERE Member since: February 17, 2015 Posts: 5 777]

^ When I built the 4L65e I really did it out of technical interest. I had never built one before, actually never even pulled one apart. But I built it when I was “just” going a mild LS3 update. At the time, (over 3 years ago farken!!) I pretty much had what I thought were the best parts I could find, at the time consensus was for the power/torque levels of a stock LS3 (420ish) street driven, what I had specced would be fine, i.e. no need to upgrade the pump rotor. Then I changed tack to the 454 everything sort of changed, and I always new the 65e was on borrowed time. Actually I think the fact a first off, home built, 4L65e has lasted this long (not withstanding the second clutch pack being fried by an inattentive tuner) I am pretty proud of But its a matter of time, hence having a bullet proof glide waiting in the wings…

• This reply was modified 9 years, 8 months ago by  VRSenator065.

[Anonymous View build HERE Member since: January 1, 1970 Posts: 0]

Ahhh check!

Mine failed driving on Cruise control….

[VRSenator065Participant Adelaide SAVR Senator LSx454 1960 Kombi (project) 1921 Nash Hot Rod (future project) View build HERE Member since: February 17, 2015 Posts: 5 777]

My issue with the Pedders rear springs is that by having the adjustable base its just means the spring physically is much shorter. Look at the difference in actual spring from the yellow King on the right to the Pedders red on the left. This means it will be simply firmer, it has to be or it will bottom out. Actually in a true race car you want soft springs but heavily damped. Having firm as fark springs makes the car skate, which is great for street “drifting” but not actually what you want for lap times. Everything I have heard on the strip is that getting an IRS to hook up is having a similar set up, I hear guys use FE2 springs which are hardly stiff. My total guess based on some knowledge of chassis set up and suspension is if you have a very stiff spring in there it will break traction too easily, softer springs will allow the rear to squat and absorb the torque helping to grip. Thats why drag cars use large side wall tires not low aspect ratio I assume for a similar reason to allow them to absorb that hit of the gas pedal.

• This reply was modified 9 years, 8 months ago by  VRSenator065.

[Anonymous View build HERE Member since: January 1, 1970 Posts: 0]

Downside to that theory is too much squat = lots of Camber change and you ride on the inner edge of the tyre, it loses tractions un squats = less camber then you get a big grip so it squats again …. rinse repeat… (sound anything like what would cause axle tramp?)

[VRSenator065Participant Adelaide SAVR Senator LSx454 1960 Kombi (project) 1921 Nash Hot Rod (future project) View build HERE Member since: February 17, 2015 Posts: 5 777]

Lets face it, Commodore IRS is pretty poor geometrically, that’s why someone I have recently got to know has gone out and built his own ;) I suspect the FE2 is a good compromise between too much suspension travel and being too firm. I also wouldn’t mind betting guys running 9’s in IRS commies would be all over how the rear is set statically, and I get its not standard…

Axle tramp, now that whole new ball game. I wrote a whole spiel on that a while back, to me the fact that G Force have cured axle ramp by just fitting drive shafts of two varying diameters to me shows its not really to do with camber change, its to do with a resonance in the rear drive train, decouple the resonance, eliminate tramp. Lets face it, yes there is camber change, but you are on a tire with maybe 16 psi with a fat sidewall, its not that severe on the strip… If I can find my musing on axle tramp i will post it up here for interest/discussions sake…

[VRSenator065Participant Adelaide SAVR Senator LSx454 1960 Kombi (project) 1921 Nash Hot Rod (future project) View build HERE Member since: February 17, 2015 Posts: 5 777]

This is why I am just so sad at the demise of SC, my old thread had 100+ pages, 4000+ posts, 270,000+ views. rip.

This is what I wrote about tramp over a year and a half ago, its just my opinion, please don’t flame me for it.

Axle Tramp
Traditional axle tramp on a leaf sprung car was the rapid winding up of the leaf spring into an S shape, then unwinding over and over very quickly causing it to “tramp” Live axle Commodore rears dont use leaf springs so dont get tramp. In the old days we used tramp rods that basically bolted underneath longitudinally underneath the leaf spring to stop them being able to go S shaped so it sort of stopped the tramp.

In a Commodore IRS, axle tramp is a very different but in some ways similar thing. Axle tramp in an IRS system is caused by a resonance in the rear drive area. What makes it harder to understand is that there are so many more components that make up a Commy IRS rear end. All of the components work together and they all sort of come together to effect the frequency (the vibration rate) and amplitude (how harsh it is) of the tramp. That’s why some people swear by loose bushings, or a car that did it, after doing some small changes to the rear end, even just diff ratio may not anymore.

What is the Solution?
To me running the rear “loose” is a pretty crappy way to try and solve the issue. Suspension geometry is just so important to handling, braking, and general ride, as well as dramatically effecting tyre wear etc.

Companies like G Force (there may be others) have solved the problem another way. They have come up with the very simple but extremely clever method of making the two drive shafts slightly different diameters. In engineering terms small diameter changes have a huge impact on their resonant frequencies (Actually very small changes in shaft diameters make huge differences in a lot of properties of shafts) and now because they are different it decouples them and so it virtually eliminates the tramp.

Of course the problem is they are not cheap, but neither is replacing rear end after rear end as it basically tears itself apart.

How to build a good Commy rear end
Its important to recognize that on an IRS Commy the rear cradle is held to the car at the two ends of the cradle and the rear diff mount. So the entire torque, rear braking force and drive of the car is taken out through those three points.

So a good start is to fit good quality bushes to the sub frame, and a Harrop diff cover is a good addition for the central mount. Then I think strengthening the rear sub frame is a must, obviously I went a little extreme, probably just an extra top plate on a mild HP streeter would be good. So now we have a nice strong positively located rear sub frame. Then its good quality bushings in the training arms and you might as well fit caster/camber adjusters while you are at it. Then good quality shocks and springs. Then add some G Force style drive shafts, and I think your are good to go.

[vs manta 218Participant Vs hsv manta View build HERE Member since: March 2, 2015 Posts: 796]

I do know what your saying but I highly doubt the springs in this kit are stiffer then what most use in race car

And the sets up vary a lot Iv seen some where they squat Incredible redulious amounts and others that seam stiff as and both seam to launch with the right tyres on

[VRSenator065Participant Adelaide SAVR Senator LSx454 1960 Kombi (project) 1921 Nash Hot Rod (future project) View build HERE Member since: February 17, 2015 Posts: 5 777]

Agreed and lets face it the geometry of a commie IRS set up is so poor, we are talking about how well you can polish a turd. Some things though (with me anyway) I think coz of my mech eng back ground are more about principal than actual absolute truth. But that’s the good thing about car building, we get to express ourselves in how we approach things, bloody boring if we all did the same stuff all the time.

[vs manta 218Participant Vs hsv manta View build HERE Member since: March 2, 2015 Posts: 796]

Definetly poor suspension geometry in commodore that’s for sure

It where HSV should have picked up it’s game and designed it’s own suspensions geometry fitted to it’s models

[VRSenator065Participant Adelaide SAVR Senator LSx454 1960 Kombi (project) 1921 Nash Hot Rod (future project) View build HERE Member since: February 17, 2015 Posts: 5 777]

^ 100% agree with that. In fact I would have thought making a drop in replacement suspension as a sub frame picking up on the original sub frame mounting points should have been half possible. But I think back in the day of ours just making 185kW was a big deal

If I did mine all over again from a bare body, truthfully I think I would have looked around for a live rear, so much easier to get to work.

[vs manta 218Participant Vs hsv manta View build HERE Member since: March 2, 2015 Posts: 796]

If I run HSV I would have done lots of things different

Should have taking the model then made little changes such as widened the rear tubs slightly and make a decent sub frame and thrown them stupid swing arms so far they forgot how they where made and come up with double wish bone set up and be able to fit some decent tyres under it

Should have thrown the front K frame in the bin and designed double wish bone for that as well

Should of made different gaurds that warped over the wheels a tad more to get a lower sleaker looks

Back in the GTO days they should have designed a wide body version with pumped front and rear guards with a wide track and maybe lowered the roof 1-2 inches for that sleek look

Doesn’t matter if it was $100-150k or even more I bet they would have sold like hot cakes, look at the w427 all that really was is a 7L in a GTS with w427 printed on the seats and a piece of carbon fibre on the boot with the biggest brake and people couldn’t grab there cheque books quick enough

But that’s just me I’m sure not all will agree with me

[VRSenator065Participant Adelaide SAVR Senator LSx454 1960 Kombi (project) 1921 Nash Hot Rod (future project) View build HERE Member since: February 17, 2015 Posts: 5 777]

Narva*2010 wrote:

When’s the roadworthy booked Gary?

Sorry mate, missed that one, just actually got off the phone to Doug, hate to say it but he didn’t get the report finished over the break, he is aiming too this week end. Cant do much about it really, have to say I am as frustrated as hell, not with him at all, its the nature of the game, just at the delay in general. Nothing I can do about it except wait really. This delay is killing me :(

[SSEN8R VS #1081Participant Brisbane, North Side\'97 VS II HSV Senator 185i View build HERE Member since: March 16, 2015 Posts: 227]

Good write up on axle tramp Gary!

I used to get axle tramp something chronic – replaced all the shocks/springs/bushes/camber-toe kit and put in whiteline diff mount insert… BUT still get axle tramp once in a while :( Got told that the wheel alignment was perfect after camber-toe kit… Definitely a reasonance frequency thing as it only happens at certain times/wheel speeds.

My build thread - http://www.commodoresplus.com.au/forums/topic/vs-ii-senator-185i-1081/
My track day thread - http://www.commodoresplus.com.au/forums/topic/lakeside-track-sprint-day-second-go/
My VS brake upgrade thread - http://www.commodoresplus.com.au/forums/topic/vs-brake-upgrades/

[VRSenator065Participant Adelaide SAVR Senator LSx454 1960 Kombi (project) 1921 Nash Hot Rod (future project) View build HERE Member since: February 17, 2015 Posts: 5 777]

Thats exactly why I think it’s a resonance thing, it’s how the whole assembly acts as a whole. I actually worked for 5 years worked for a company called Resonance Technology, I am not saying I am an expert, but I do understand how it works. Look at the Tacoma bridge, or pushing your kid on a swing, small inputs make a big difference.

[Anonymous View build HERE Member since: January 1, 1970 Posts: 0]

Interesting, the Harrop cover settled mine in the Tonner 0 tramp once fitted, back to a stock Open diff now but the 5.7 doesn’t have enough grunt to spin the rears so not sure if it tramps or not.

[cava454Moderator 93 VR BT1 View build HERE Member since: February 20, 2015 Posts: 2 390]

Never had a tramp in mine. Stock ass end with the odd nolthane bushes.

 

 

 

[vs manta 218Participant Vs hsv manta View build HERE Member since: March 2, 2015 Posts: 796]

You had auto don’t you cava ??

Never heard of a auto tramping

Seams to alway be t5 manuals but I’m sure a auto has before somewhere along the line

Myn tramped for years, stoped when I rebuilt diff and changed LSD centre

Rebuilt diff years earlier using same centre and didn’t change anything back then

[cava454Moderator 93 VR BT1 View build HERE Member since: February 20, 2015 Posts: 2 390]

Mines used to be t5. Now stalled auto

 

Hopefully the new setup doesn’t tramp. Gone solid ass end

[vs manta 218Participant Vs hsv manta View build HERE Member since: March 2, 2015 Posts: 796]

Are ok, cool, you where lucky ones with a well built car

I broke so much shit in my car, distroyed 2 clutchs, a gear box, diff, rear axels, ripped 2 cradles apart, severly distroyed rear shocks

Then I got sympathetic and stoped doin hard 1st-2nd-3rd changes

Finally 700hp and a new diff solved it

Have never tramped since building car and it doesn’t get any traction these days

The only thing I can put it to is the LSD diff centre

• This reply was modified 9 years, 8 months ago by  vs manta 218.

[cava454Moderator 93 VR BT1 View build HERE Member since: February 20, 2015 Posts: 2 390]

Yeah touch wood I never broke anything. I used to give it curry also lol

 

Come to think of it, I still do

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