VN Diff Shortening

[ekdave1962]

Channel your tail shaft tunnel?

yeah thats a last resort option .. was hoping maybe longer shocks of shocks with a heavier compression setting .. may do the job .. i think ill take it pedders tomorrow to see what they have to offer

[Errol62]

Is it squatting or rotating the housing so the pinion rises. Probably a combination of both. Tramp rods were common on muscle cars on the 70s and this could solve the problem. Could even try fabricating a rough set from angle to see if it works.

[Harv]

Mmmmm.... tramp rods....

Info below may be useful for some quick fabrication:

Lakewood traction bars.jpg (94.93 KiB) Viewed 2279 times

Tramp Rods.pdf

(108.93 KiB) Downloaded 140 times

Cheers,
Harv

[bat53retro]

g'day all
if under acceleration the tailshaft hits the floor the springs need resetting
had the same problem reset springs and used pedders shockies that are used on hq race cars
sorry can't remember the number


cheers bat

[ekdave1962]

g'day all
if under acceleration the tailshaft hits the floor the springs need resetting
had the same problem reset springs and used pedders shockies that are used on hq race cars
sorry can't remember the number


cheers bat

thanks bat

yeah i suspected the springs it booked in to pedders next week for assessment .. what was the cost ?

[FireKraka]

Hi Guys;
I believe the tailshaft hitting the tunnel is due to the pinion being offset; if this is how you have shortened your diff; if not then the problem has already been discussed.

I have shortened 2 diffs one for standard track FC and the one for my ute to fit commodore rims; I know it is easier to have 2 axles the same size but I don't agree in offsetting the pinion.

Just my opinion
Regards
Neil H

[kelleigh54]

OK , my penny's worth . Depending on the amount of torque you are putting through your drive train may be relative to the means of a fix to the situation .
But , bottom line is the combination of lowered springs or lowering blocks and larger pinions and tail shafts is going to lead to this problem regardless of shock quality , springs being reset , additional leaves or any other quick fixes that we all come up with ( yeah , I am guilty too ). Both the sons and my EK's suffer with this problem. I run a 9 inch and 1350 uni's and he has the borg warner ( c/dore ) rear assy and pinion . We both have Koni adjustables , reset springs , new bushes and spring pads etc etc . He runs a staunch 202 and mine a small block , I have cut to relieve the rear section of tunnel and also above the diff centre . This is not a fix ! just another part of the overall requirements to resolve the issue on my car . The true fix is to install tramp rods or caltrac style devices to restrain the loading on the front half of spring which loads up , releases ,loads up , releases and on and on it goes creating axle tramp . Spring wind up seams more chronic with moderately powered leaf rear ends than it is with the higher power through leaves , as it is far easier to brake traction which relieves the loading and just cuts loose instead .
A couple of other insights regarding this is , I have found the use of lowering blocks has a fulcrum effect on the springs which amplifies the spring wind up . This is probably not as noticeable on a mild red 6 but none the less it would have an effect . This is only my assumption on issues I have experienced , nothing scientific about this at all .
But one thing that is a fact is if you choose to use the Caltrac style and you have reversed eyes on your springs , then you are in for a few modifications to make it all work as it was not designed for an eye on the underside of the spring and the only way around this without another set of springs is to refabricate the plates that are to be installed at the front eye . Anyway ,In short , bite the bullet and fit some tramp rods or caltracs and most likely save a lot of other mods and headaches . Creating clearance so your pinion can do a tap dance without the noise is not resolving anything and eventually you will have a failure .

[Errol62]

I have to agree with Leigh. Lowering blocks don't sit comfortably on my head regarding suspension geometry. Tramp rods are an obvious fix and easy to fabricate if you can't find a set although they are not an elegant solution. Don't know anything about caltracs. Prettier than tramp bars?

[bat53retro]

g'day all
have 3 modified cars
fb wagon v6 shorten com diff
fx sedan v6 s/c shorten com diff
eh pv v6 s/c shorten com diff
all have offset pinion 2" as standerd diff has

[bat53retro]

sorry didn't finish
none are running tramp rods or hit the tunnel

[Errol62]

"None are running tramp rods or hit the tunnel"

I take it you are running lowered leaf spring suspension bat?

[bat53retro]

all the cars ar lowered
fronts are lovells hfl1 hq stubs
rears are leaf reset about 3" from standard

[Errol62]

Ok bat so race spec shocks will be very firm thus reducing tramp effect. I get that.

Resetting the springs would only vary the ride height or have they been stiffened as well?

[kelleigh54]

Hey Bat ! Your not driving it hard enough

[bat53retro]

when the springs are reset by wa spring works
according to them it also stiffens them
i know when you are side ways there is little weight on the springs