Drivetrain Resonance and other possibilities? 1st gens blowing gearboxes

[Wiretap]

Righto... so here's the deal

Drunkenmonkey's car: blown 1st gear twice, was fine with lowered (and very stiff suspension) for quite a while, but within a couple of days/weeks of the addition of 16" TE37 wheels, BOOM goes 1st, and now, the replacement gearbox has just done the same

My BC5: been through a lot of gearboxes bought cheap, failed for various reasons (usually bearings), latest gearbox was a bit chatty in 5th, but fine otherwise, always had TE37 wheels, just fitted ver8 STi suspension with STi aftermarket Race springs... within a week I'm missing a tooth off first gear.

Other strange symptoms: when driving on the motorway in 5th, from time to time both cars will experience a vibration that can only be described as driving over hundreds of tiny bumps, it fades the moment you change speed, but fades in and out if you stick to one speed, no suspension bushes are out of spec or failed on either car.

My Theory: Drivetrain resonance? A combination of the very light wheels, and very hard suspension, could possibly be setting up a torque-resonance through the gearbox that is literally vibrating everything to death?

I'm keen for other ideas, because this doesnt make a huge amount of sense to me either.

[Guest boostin]

My bet is old Gen 1 RS gearboxes that have had a hard life are finally dying. Use something a bit more reliable like a GTB or STI box.

[BC5RA]

 boostin said:

My bet is old Gen 1 RS gearboxes that have had a hard life are finally dying. Use something a bit more reliable like a GTB or STI box.

Agreed; less use of cheap gearboxes.

[Wiretap]

 boostin said:

My bet is old Gen 1 RS gearboxes that have had a hard life are finally dying. Use something a bit more reliable like a GTB or STI box.

Gearbox years (the ones that are confirmed):

- 1993

- 1997

Not Gen 1 RS gearboxes.

GTB gearboxes will be replacing them, but if its resonance at fault, that wont stop them blowing.

[Guest boostin]

Well if you're running hard suspension and light wheels you should be bending wheels too.

I've had no issues running a non-205kw twin turbo box for 2 years now, and most of that on ~180kw atw. I can only guess you've simply had a bad run of gearboxes.

[Guest keltik]

Ive beat the snot outta my 93 GT box with no oil in it for 25,000kms now. Whines a bit/lot but shifts perfect. Have killed clutches and engine mounts before breaking gearboxes.

Torque resonance doesnt sound likely at all. Sounds like old worn out boxes being driven harder than whats sensible

[Munkvy]

I limiter launch with a bit over 200kw on semi slicks on a V3 RA box. Still going so far Mind you Ive probably only done 50 launches on this gearbox.

[dubbedup]

3 gearboxes in my old 98 rs....lowered on big wheels....none in my wrx...yet,

I think dodgey engine mounts had a large part to play...

Edit - all 3 boxes were front diff, and all were turning right.....at aprrox 20kms

[Wiretap]

 boostin said:

Well if you're running hard suspension and light wheels you should be bending wheels too.

I've had no issues running a non-205kw twin turbo box for 2 years now, and most of that on ~180kw atw. I can only guess you've simply had a bad run of gearboxes.

Bending wheels has what to do with what exactly? TE37s are not exactly known for bending, more like shattering if hit too hard...

Also, we're not talking about failures due to abuse here, all three failures were at random, during periods of fairly quiet driving

- Drunkenmonkey's first one lost a tooth while pulling out of an intersection normally.

- Mine lost a tooth while turning around after pulling out of someone's DRIVEWAY!

- Drunkenmonkey's second one, again, intersection, with no thrashing.

Sorry guys, but I did go through all the 'normal' possibilities before I arrived at this, I just don't think its anything simple, and it still doesnt explain the way the vibrations build and subside in a wave...

[kamineko]

think its safe to say no-one can explain it. is your driveshaft all good? your half shafts straight? bad hub bearings may also be giving you vibration?

[Guest keltik]

So this vibration thing.... You mean like clints wagon used to have?

Go watch the video of him at pukekohe and youll hear what i mean

[Wiretap]

 kamineko said:

think its safe to say no-one can explain it. is your driveshaft all good? your half shafts straight? bad hub bearings may also be giving you vibration?

Hub bearings are good, halfshafts are good, as is the driveshaft, I checked all of these, and if it was any of those, I would be doubtful of it occurring at the same time on every car.

I'm not so much looking for an explanation, as some input, because if it is this, I don't want to keep going through gearboxes.

[Guest boostin]

Actually now that I think about it, mine had a light vibration that would come and go at motorway speeds. It started after I did the manual conversion. I put it down to a dodgy pick a part prop shaft. I haven't felt it for ages now though.

Re the light wheels comment, I meant that hard suspension and light wheels normally ends up with bent wheels, which also causes vibrations. I've never seen a gearbox damaged by suspension and wheels.

[Guest keltik]

Nakkered center carrier bearing on the prop shaft will cause a bit of a shudder under acceleration. The one on my Honda went bad and caused a bit of a hassle.

[ODB]

Oh noes!!!

Feel the vibration!!! This thread has lots of resonance with me!

[BC5RA]

Coincidence and bad luck.

[Guest]

What clutches are you using? ,

launching fractures gears then they usually fail when just cruising along

[Drunkenmonkey]

 Wiretap']

[quote name='boostin said:

Well if you're running hard suspension and light wheels you should be bending wheels too.

I've had no issues running a non-205kw twin turbo box for 2 years now, and most of that on ~180kw atw. I can only guess you've simply had a bad run of gearboxes.

/quote]

Bending wheels has what to do with what exactly? TE37s are not exactly known for bending, more like shattering if hit too hard...

Also, we're not talking about failures due to abuse here, all three failures were at random, during periods of fairly quiet driving

- Drunkenmonkey's first one lost a tooth while pulling out of an intersection normally.

- Mine lost a tooth while turning around after pulling out of someone's DRIVEWAY!

- Drunkenmonkey's second one, again, intersection, with no thrashing.

Sorry guys, but I did go through all the 'normal' possibilities before I arrived at this, I just don't think its anything simple, and it still doesnt explain the way the vibrations build and subside in a wave...

actually first one i noticed when i pulled into chris's workshop at idle!!!

[Wiretap]

 Ichi Ban said:

What clutches are you using? ,

launching fractures gears then they usually fail when just cruising along

Both using standard clutches, and dunno about matt, but I avoid launching, because everyone knows that TY75's dont like shock loading.

[Guest keltik]

 Wiretap said:

because everyone knows that TY75's dont like shock loading.

Everyone?

[Guest]

BS

[ODB]

 Ichi Ban said:

BS

Gold!!

You definately are Ichiban!!

[ODB]

 Wiretap said:

Righto... so here\'s the deal

when driving on the motorway in 5th, from time to time both cars will experience a vibration that can only be described as driving over hundreds of tiny bumps,

Are you sure you actually werent, um driving over hundreds of tiny bumps ie something like road that hasnt been smoothed out yet or something like that???

you sure you dont have anything else in the drive train set up incorrectly??

[gtlegacy]

this is weird perhaps seeing its old boxs the bearings inside the gearbox have done hard yards and showing a bit of wear which in turn gives it a bit of slack through the system maybe thats what you can feel? and being an old box you dont know if the last owner raped the ass off it and said its mint

just an idea

gen 2 legacys non b spec would be a good upgrade i think as dont the early cars run 4.111 (mine did)

[Drunkenmonkey]

i ended up going 4.44 gtb box mates at the wreakers gave me the diff for free