[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.

[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]

Imho 90% of longevity of a 4L60/65 is about the tune. Or more importantly the tuner understanding (and accepting) the requirements of the hardware. Problem is for most of us there is a disconnect between the tuner and the auto builder = trouble…

[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, 7 months ago by  VRSenator065.

[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, 7 months ago by  VRSenator065.

[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 one of the new Sonnax billet input drums with the bolt on supporting ring isn’t it? They weren’t out when I built mine but Greg Nader at Sonnax who i got to know said they were working on something like it. very nice bit of kit.

[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]

Hi mate, tbh I don’t truly know what the colour code is for the wheels, I just asked them to copy what they were, but I will see if I can find out for you tomorrow.

I have King SSL rear springs when you see it sitting the nicest. Right now I have Pedders with the adjustable pad in there, that’s so I could adjust the ride height to get it legal. Tbh I dont like them as you sacrifice spring travel, so ride quality is compromised/harsher.

[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]

To be honest, I don’t really understand what it means. I am a bit of an old fart and don’t download moves (yet). So what exactly does it mean, if you do from now on you can get sued, or if you have in the last two years you can?

[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]

^well,that’s about perfect for me, what cool skils you guys have, makes me want to build one!

[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]

I think it’s a fair comparison and a good discussion. It’s comparing what’s available today with what’s available today. It’s started out of a discussion as to whether it’s worth doing LS swaps. The fact the technology is newer for the LS than the Holden is exactly the main reason I went to it. I don’t buy if Holden kept up with the V8 it would have ended up as good as an LS, the SBC is a much better engine imo than a Holden, and yet chev ditched that to go to the LS style, so even they knew there was only so far you can flog a dead horse before you start again. Which they did and by any measure created a magnificent design and architecture in the LS with huge potential.

• This reply was modified 9 years, 7 months ago by  VRSenator065.

[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]

Hell yea, getting there, now your talking

[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]

I don’t think you are right about the LSx and emissions, at least here in SA I have had to comply with the emissions laws as they stand now i.e. current in a 93 VR.

[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]

VPGTS76 wrote:

Bit on ATM

your telling me, I’m busier than a one legged man in an ass kicking competition!

[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 advice if you are starting to modify your car, and you are also worried about money. Put down that spanner, slowly back away from the car, close the shed, lock the door and go and take a good lie down….

You will spend more than you wanted too, it will take longer than you expected, and no matter how much power you make or what time you run you will always want more. And as I said before HP costs…

[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]

The VR looks very cool. I reckon you have the roof line close on the bottom two, but it would need the width of the normal B pillar to make it work. It would also have to have a one piece glass section behind the door. Very cool, thanks

[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]

You really want to use an image hosting program like photobucket, I did a write up on how to use it if you haven’t already. Then the image size is much larger and instead of just showing up as a thumbnail its full size

http://www.commodoresplus.com.au/forums/topic/posting-images-using-photobucket-attachments/

[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]

Perfect, never really taken any notice of one before, cheers for that. All goes into the memory bank

[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]

Apologies for the dumb ass questions btw, but I am very new to the LS world, so far my engines been essentially stock crate so I haven’t done too much with it (yet). I assume the large toothed disc at the rear of the crank is the reluctor wheel? Are the 24 & 58 the same size essentially, just with different tooth count? I am currently running the Lingenfelter converter, but if the engine is ever out I plan on swapping it. By the look of it you have to pull the crank entirely out to do it?

Btw not thinking of a split timing case? Makes cam swaps way easier.

[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]

Thanks to my local Holden spare parts dealer, these are the sensor plugs off the L98

[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]

Thanks to IJ for the pictures and info for the L98 & LS1.

If anyone has any other info to add feel free to post it up or message me and I can include it.

[Author]

Posts