New Diff - axle tramp and engine/exhaust labouring ... can someone explain to me why?

[FrangaFry]

Hi folks, on my never ending quest to actually learn something (or just sound like an idiot); As the title suggests, I have recently had a complete diff change.

I drive a VYSSII wagon with a Harrop HTV1900, the suspension has been upgraded (Koni adjustable all round and Whiteline Sway bars front and rear, with the Diff cradle bush and few others being changed as well). My old Diff had 3.73 gears in it and the new Diff (complete Diff swap, not just gears) has 3.45 gears in it.

Previously I had not experienced any axle tramp when 'accidentally' turning the tyres (it's easy to do with the blower.....); I have noticed since getting the new Diff that (especially in the wet) when the wheels are turning (by accident of course - seriously), the car sounds like there is a jack hammer going off (it seems MUCH louder on the driver side than passenger.. but this just may be b/c that is where I am sitting...) and I have to back RIGHT off really quickly (the noise is SOOOOO loud that it scared the crap out of me when it happened, as I just wasn't expecting it ... my daughter was in the car the other day and taking off a little quickly the tyres turned and the noise freaked her right out - it's REALLY loud). With the old DIff I NEVER experienced axle tramp even with the blower (it was as smmmmmoooooooth as a babies bum even when the wheels were spinning,wet or dry, not that I do it intentionally, HONESTLY!!).

Added to the above I have also noticed considerably more 'drone' and vibration through the car and the engine seems to labour a bit on acceleration (say cruising at 80 and put the foot down slowly to accelerate smoothly to 100 it moves due to the blower but the engine seems to labour... there seems to be a completely different sound and vibration out the back than there was prior to the Diff replacement?)

Does anyone have an explanation for this (tweaking was made to the EFI live setup to cater for the gear ratio change)? I love the new Diff and ratio (as the old was seriously noisy) but the axle tramp issue is seriously p1ssing me off and the drone in the exhaust and extra vibration in the car is getting to me as well (it just seems so much different and the only ting that was changed was the Diff and gear ratio).

I am reluctant to hassle the tuner/mechanic at this stage, as he has been great in the past and I have had to go back and hassle him more times than I would have liked over the previous Diff and I just don't want to sound like a complete whinger and piss him off until I know that this issue is actually normal?

If it is normal, and the issue is just due to the new ratio (tyres not turning as quickly with the new ratio???) then I might have to seriously consider going back to the 3.73 gears as the axle tram is just TOOOOO much (and with the blower the tyres tend to turn way more than you intend).

Any advice?

Thanks in advance,

[JezzaB]

To get axel tramp you need some grip. Now you have a different ratio you arnt spinning the tyres as quickly with no traction at all. Droning because it is loading it up more and labouring as you suggested. Its a side effect but you will get more out of each gear and more grip and then pushed back in the seat more. You want more wheel spin and faster changes, put the old diff ratio back in or cheaper tyres or look at the suspension setup

Turbos love that loading, it makes them work harder. Blowers dont gain the boost from the loading but they gain the traction and pushing back in the seat.

[FrangaFry]

To get axel tramp you need some grip. Now you have a different ratio you arnt spinning the tyres as quickly with no traction at all. Droning because it is loading it up more and labouring as you suggested. Its a side effect but you will get more out of each gear and more grip and then pushed back in the seat more. You want more wheel spin and faster changes, put the old diff ratio back in

Ok, so this is normal then. I really do like the new ratio, as you say, it seems allot stronger and I seem to have more mid range and top end (with the 'push in the seat' feeling still very much there from a start) and the wheels don't spin as much in the dry. So, this is all part and parcel of the setup I have... is there anything that can be done to reduce the axle tramp (it's really only a problem in the wet but god damn it's loud and when it does happen every head within 100 meters turns to look at the :jerk: ...... maybe I just need to pull my head in when its raining).

And the drone and vibration is normal as well?

I did like the 3.73 (quick as of the line) but the wheels did turn too much and I noticed the mid range and top end power loss. The 3.45 gears seems to suit the blower so much better. So the advice is live with it and change my driving style or put the old gears back in? Hmmmmm...........

Edit, maybe a blower cam will help....... :rolleyes:

[VY-SV8]

hi mate,

i had issues with axle tramp too when i hit the strip and what helped out for me was swapping over the rear bushes to polyurethane item. i swapped all of mine over to superpro items and you'd be surprised how much it helped. good luck getting the dreaded tramp sorted, it is a real pain when it rears its ugly head.

[FrangaFry]

hi mate,

i had issues with axle tramp too when i hit the strip and what helped out for me was swapping over the rear bushes to polyurethane item. i swapped all of mine over to superpro items and you'd be surprised how much it helped. good luck getting the dreaded tramp sorted, it is a real pain when it rears its ugly head.

Thanks for the feedback guys, I am feeling a little better about the issue. Given that I have recently installed Konis on the rear and a whiteline sway bay (with supplied bushes) + the diff cradle, can you let me know which bushes you would recommend changing (with the Super Pros I assume?)

Cheers,

[VY-SV8]

when i did my bushes, i did pretty much all of them, front and back. however for your situation i'd guess you only need to do the rear ones. I'd suggest the following, although i'd be happily corrected from someone more in the know.

1. Rear subframe bush mounts
2. control arm bush
3. camber adjust kit

i assume you have already done the sway bar mounts when new sway bars went in. this is pretty much all i did, but i'd be starting at the top of that list, the rear subframe bushes would be the most beneficial to swap out to help you in your situation, however the control arm bushes are easy to do while you are already there. The camber kit i did as with a lowered commodore IRS set-up you end up wearing out the inside of your tyres with the typical "commo squat" i call it, so it was easier and cheaper to get the camber fixed than wear out my $400 tyres. The rear end grip is better too now i have more tyre on the road.

hope my ramblings help a bit, i'm no expert but i tend to listen when someone who knows their shit is talkin. So i have picked up a bit over the years.

[Wonky]

Chev often does complete bush swaps through the whole car with (I think) Pedders and in fact I'm surprised if your bushes were anything but in good condition he wouldn't have suggested swapping. On the other hand I know Ron SS has done a lot of research into VE axle tramp and suggests that replacing ALL bushes with the solid ones actually contributes to axle tramp!! See http://www.g8board.com/forums/showthread.php?p=856142#post856142

[VY-SV8]

Chev often does complete bush swaps through the whole car with (I think) Pedders and in fact I'm surprised if your bushes were anything but in good condition he wouldn't have suggested swapping. On the other hand I know Ron SS has done a lot of research into VE axle tramp and suggests that replacing ALL bushes with the solid ones actually contributes to axle tramp!! See http://www.g8board.com/forums/showthread.php?p=856142#post856142

He says in the first post he has a VY SS wagon brother, so the VE dealio doesn't apply. hence why i responded with how i fixed my VY axle tramp issues.

[Wonky]

Yes I know he has a VY because I've met him quite a few times, but what I'm saying is that Ron's research doesn't just apply to VE. What he has found applies at least to some degree on pre VE also. If you remove all flex by installing solid bushes at every possible point you potentially increase axle tramp.

[VY-SV8]

wonly i am not too sure that you linked the correct thread, i read through all of that thread posted but nothing came up that would show using poly bushes would increase axle tramp. Infact in every instance i have used poly bushes it has helped to eliminate wheel hop.

[1BEAST2NV]

cant really do much about the drone in the car,

with the 3.7's the revs would have been in that spot where it was past the drone point.

Now with 3.45's its at the point in the rev range that the drone is noticeable.

[Wonky]

That single post and the thread it's in probably don't explain why poly bushes increase axle tramp, but I have a whole DVD Ron made showing axle tramp, suspension geometry etc etc and the one thing he is adamant about, as illustrated in the DVD, is that replacing all rear bushes with poly will actually increase tramp. A few key phrases from that post he did are "This MUST result in the rubbers/poly bushes at the cradle end to squish up to allow for this geometry change." and "If you use stiffer material than the standard rubber, and use poly for example, then the control arm and trailing arm will soon wear out the material simply because the geometry is forcing it to squish up to make up for the misalignment. Rubber does this very well, poly does not. Eventually the poly "hole" becomes oval, as indeed this thread has shown. Poly mounts work by having the ferrule rotate with the poly, as it is NOT bonded to the ferrule like the std rubber joint."

He has cured his axle tramp in the dry 100% but hasn't yet solved it perfectly in the wet.

[Wonky]

:doh: Forgot one important paragraph from that post of Ron's that I guess VY-SV8 missed too:

"suppliers of poly bushes, and you know who they are, simply do not understand this geometric misalignment issue. My advice is to stay with the standard rubber bushes, or use rod ends, but only at the inner mounts. The joints at the knuckle end MUST squish up to allow for the toe arm to do its job and change the wheel angle to end up with (close to) zero toe change. Hard bushes or rods ends at the knuckle will not allow toe correction and will probably end up binding the wheel. The thing that amazes me is that it has taken some two years for these issues to finally show up ... a simple, look at the geometry is all it takes. "

That applies to VE/G8 specifically but I'm pretty sure from my interactions with Ron that it also applies to pre VE, at least to some extent.

[VY-SV8]

the rear cradle is completely different in the VE to the VY, so i am failing to see the correlation between the VE rear suspension design flaws and those of the previous models.

I did read that post and yet i can't seem to comprehend why he would think that a "misalignment" in the front LCA bush would cause wheel hop, that bush is only there to aloow the LCA to pivot up and down, in most instances you will find that front pivot is even welded to the frame i have found. So using a rubber mount bush in that particular instance baffles me as using stiffer components or bushes has been the solve for that issue even from manufacturers.

I digress, but i would be interested to learn more as i may be on a different a page to what you were referring to. I can only really comment on what i have heard when talking to my suspension guy and from people i believe to really know their shit when it comes to going fast and in every instance i have come across using stiffer poly bushes in certain areas in the rear end my axle tramp is now gone. Miracle cure... maybe, but it worked for me and many of my friends in their VY's so i can only recommend doing similar.

shoot me a PM and i'll search out that DVD you speak of so we don't clog up the OP's thread.

[Wonky]

shoot me a PM and i'll search out that DVD you speak of so we don't clog up the OP's thread.

Yes, agreed - I'll stop clogging up this thread. :yup: Apologies to the OP. :)

[VY-SV8]

Yes, agreed - I'll stop clogging up this thread. :yup: Apologies to the OP. :)

me too, sometimes i forget where i am posting as i quest for more knowledge. Good luck solving the dreaded "bounce" mate.

[1BEAST2NV]

I was under the impression that everyone thats had problems with VE 's with axletramp have changed there bushes to nolethane/superpro bushes and the axle tramp has been drematicely reduced ,or next to gone...

and that was from changing out the rear cradle bushes etc along with the other rear bushes..?

Find it abit strange 1 guy's dvd says one thing, then alot of suspension shops say another!!!!!

[dogsballs]

some people have had more issues in the VT-VZ with poly vs rubber. I'll throw my 2c in and say it could be the rear shocks if they are pretty rigid.

all i know, with FE2 rear springs and shocks and diff mount, never had tramp in my VZ's (drag racing as well). NOTE: watch the tramp as it has a tendency to kill diff centres. :(

[FrangaFry]

Thanks for all the info folks. I think I now understand 'why' I have tramp (cheers Jezza) and drone (thanks Beast) now and not with the 3.73 .......... so this is a good thing.

I'm really not cool with ==>> NOTE: watch the tramp as it has a tendency to kill diff centres. This is the last thing I need .................... (I've given Chev enough grief already....)

So if this is the case, then I might have to think a little harder about putting the 3.73's back in........ thought process is going something like this:
- It's gunna cost more bucks to replace rear bushes with no real guarantee that the tramp will be fixed.
- If tramp kills diffs, then it's gunna cost more to replace diff at some point
- I want a blower cam in the near future and the wife really isn't happy with me spending more cash on the car (so I rek'n i've got one more purchase in me before she lodges divorce papers.....)

It seems putting the old gears back in will mean resolving the drone AND vibration AND tramp issues (as none of these were a problem before the diff change - although granted, the drone and vibration are not really a problem, just 'different to the way it was)

Seems like a bit of a no brainer at this point............... although, I really do like the new gears :doh: they do feel so much smoother in the power delivery.....................

Bugger! I'm gunna have to call Chev and have 'another' chat hey, :hide: ..............

Wonky, just on the stiffer bushes, I by no means know what the hell I am talking about, but I too have heard/read from a few sources that stiffer bushes 'all round' often contributes to bounce and premature wear. From what I can decipher, a combination of plastic and rubber is the way to go. Thanks for giving me a good break down of potential bushes to replace VY-SV8.

[1BEAST2NV]

being a blown application.

have u had it down the strip with the 3.7's, then back down with the new 3.45's, if so was there much difference??


would be interesting to know.

[FrangaFry]

being a blown application.
have u had it down the strip with the 3.7's, then back down with the new 3.45's, if so was there much difference?? would be interesting to know.

G'day mate, nope sorry to say I have never had it down the strip so I can't really comment. I am torn about the gears though, as I really do like the smoothness of the new gears, but weigh this against the noise, vibration, tramp and possible diff killer, then I might just have to go back.......

[Wonky]

If I interpret correctly though the only reason you're getting tramp now with the 3.45 (3.46???) and not the 3.73 is because the 3.73 made the wheels spin faster meaning you had less traction. Whilst I can see the reasons behind a desire to go back to 3.73 in some ways it's an arse about solution because it's really just avoidance by regressing to less grip. Better if possible to try to cure the problem rather than sidestep it, though it is a tricky one! I know some different sized axles like G-Force make supposedly eliminated tramp for some people. Maybe look into that too? :confused:

[FrangaFry]

G'day Wonky, yes I know your right mate, it is arse about and it does feel like the wrong thing to do .............. i'm still sitting up thinking about it.!!!! I'll talk to Chev, he always sets me right.

[dogsballs]

sorry to throw that in there, but it can and does happen. many many threads on trying to get rid of tramp.

[Wonky]

I emailed Ron and received a lengthy response which I've hopefully edited down to successfully retain the correct essence for on here. Note that in his work on trying to cure axle tramp Ron has had a fair bit of interaction with GForce themselves.

"Tramp on the VY, or any of the IRS cars pre VE can be solved using the big and small axles like GForce make. See www.shop.gforce1320.com and look up for the GTO ...Monaro. At around $800 + shipping per set and include CVs – a good deal I reckon. The CVs in pre VE are a weak link and GForce use Porsche CVs. I also believe that cradle bushes are great for pre VE too.

Fiddling with poly bushes in the trailing arms in pre VE is a waste of time. When people claim it is improved ask them 12 months later, when the poly has become oval and the arms rattle around (same as for VE/G8 as per my post on the G8Board).

There is no doubt that using the big/small axles for pre VE works great, so I would say spend the big dollar and use www.shop.gforce1320.com axles as per their web site together with cradle poly bushes and leave the trailing arms bushes stock. Using the Harrop diff cradle is a waste of time for pre VE, it helps slightly but really doesn't do much.

For powerful cars, like the OP's supercharged VY, he will soon smash his CVs anyway and need replacement axles! Note that Harrop makes big axles for the pre VE cars. However he makes than both sides big ...hence they don't work for curing tramp.".

I will also PM the OP some extra info. :)

[dogsballs]

spending a couple k on cv's is not everyones option though.

[Wonky]

$US799 + shipping isn't bad for half shafts + CVs. Shipping won't be cheap because no doubt they're not light, but I'm sure even the stock Holden half shafts cost over half that and if it cures the problem after all the money the OP has already spent on S/C, exhaust, transmission upgrade etc it's well worth it! :yup:

[zorro]

Just incase I've missed it somewhere you changed to 3.73 and then to 3.46. What was the reason on going 3.73 in the first place, was this decided pre blower? And what was reasoning for changing to 3.46?

Tramp it seems is really vehicle dependent. Before getting too carried away try adjusting the rear shocks (Koni adjustables?) and see if that helps.

[FrangaFry]

G'day Zoro, yes the gears were changed pre blower in the first round of mods I did (standard bolt on stuff and 3.73 center change/rebuild). The diff was never right after the change (was very noisy/whiny) and Chev has been really great in trying to get it fixed. Unfortunately, after 2 center changes with non OEM gears the whine/noise was still there.

Chev has been fantastic through the whole process and it was then changed a 3rd time with OEM gears, the whine/noise was resolved but the LSD was as 'tight as' and sounded like a steel crusher when turning slowly (in/out of drive ways and roundabouts etc). To Chev's credit he then offered to do a straight swap with an entire diff (newly built), but with 3.46 gears, the diff with the 3.73 gears was then sent to the diff bloke for it to be fixed/replaced. The offer was to keep the new diff if I liked it and if not, Chev would sway it back with the 3.73 diff (seriously, you have to admire service like this :goodjob:).

I can see the sense in keeping the new gears as it seems to suit the blower better, but it has introduced some issues I really don't want to have to deal with at the moment.

Just on the shock adjustment, at the moment the shocks are on the softest settings, I would have thought going stiffer make it worse, but I am just guessing.

Wonky, your help with this is really appreciated mate, you have given me some options and food for thought :cheers: but I am seriously considering going back to the 3.73 gears as the extra cost for new axles/bushes is not something I need at the moment (I wish I had this conversation a week ago, as I just splashed out last week on some Aeroforce gauges and this could have been much better spent maybe on this issue instead :doh:.)

I really have my mind set on a cam install and that will be it for mods as far as the wife is concerned..... she has made it VERY clear ............ :slap: :bash: :box: :biggun: ..............

Decisions, decisions ............... It is a slippery slope that we embark upon when 'opening the box' on the mod monster .....................

I just want to make it very clear that the above is in no way an unhappy customer of Chev's, very far from it, I could not be happier or have more confidence in the work/advice that Chev and the boys provide..... I am just sounding out advice and previous experience.... if someone can convince me to keep the gears and fix the problem, my ears are wide open, as I really don't feel like hassling Chev again over this issue again ........... :hide:

Cheers,

[Wonky]

Clear your PMs please - just tried to send you Ron's mobile as he is happy to talk to you about it and lives not far from you.

[VL Executive]

I have not experianced tramp with my stock VY SS Ute. But (probably not really relevant to this as its an older car and live axle) I have a VL turbo, and it tramps like buggery. Its really annoying as well and I want to put a stop to it. It also has 3.45 gears and is LSD.

[zorro]

Its worth having a fiddle with the shock settings to see if it has any effect on the tramp.

The 3.73s if they are sorted Id put back in the car, the gap is not very big between them and 3.46 so an adjustment on the right foot is all you will need to be back in the no tramp area. Is the car too noisy with them in or you like the more relaxed feel of them? In saying that if you are happier with the 3.46 then stick with them and nut out what you can do to stop the tramp.

Quick question, was the traction control on? only as as if it has pulled power and re-applied it wouldnt help the tramp as the rear wheels are oscillating and the change of speed would affect the movement.

Has the tramp been replicated? could have been a poor road surface?

[johnv]

If you intend to put a blower cam in , you may find the 3.73s the better option, as the power delivery of the new cam will probably be higher in the rev range.

[Xjas]

If you are going to put a blower cam in it anyway why not do that first and see if the extra power helps overcome the axle tramp before going back to the 3.73 gears.

[FrangaFry]

OK, so I finally bit the bullet and called Chev ................ I was a little embarassed to hassle him again, but as usual, Chev is the ducks nuts. Took my wagon down today and the drone/vibration was a simple converter lockup issue. The settings have been changed and now NO drone, NO vibration - Excellent!!!!!

Now to sort the axle tramp - could also be a simple issue with the ABS/TC sensors (or with my right foot ........:hide:). So, the next wet day, Chev has asked that I pop down again to run the scanner over it (in real world conditions).

So, I am once again a happy camper. So happy infact that I am now once again counting my pennies for a small'ish blower cam install (Chev thinks i'm nuts - "Wot, it's not powerful enough for you" ............ OOOPS!"). I was asked why I wanted a cam upgrade and what I wanted out of it ................... not an easy question to answer actually (ummmmm, because I want some more ............ ummmmmm, mid range............ maybe, or ummmm, just want that little bit of 'toughness' in the ride without going silly ............ i'm glad the wife didn't ask me this).

The axle/cv's are still something that I will keep an eye on and if the right opportunity comes up, I may just have to sort this as well............... Thanks to all for your helpfull comments and a special thanks to Wonky, you are a bloody decent bloke mate and your help/advice is always greatly appreciated :goodjob:

[dogsballs]

there was a set of cv's and billet stub axles for sale on here a while ago, maybe see if they were sold. IIRC ~$1k

[stingredclubbie]

i was experiencing axle tramp problems [in a vz] and after talking to my local experienced drag racing bud, he advised fitting a harrop diff cover, being there for the instal i saw how it would tie it all together. now with full slicks and front runners at the track axle tramp is non existent [ever]. and on the street its just a dream in any conditions. good luck would louvre a ve.