Hi , this is quite hard to explain , but sometimes when i accelerate , on the 1st to 2nd gear change , i get like this jerking/jolting and it makes it really hard to control , only does it sometimes, otherwise car runs fine and and never have this problem in other gears , its hard to tell if its my driving or a actual problem , it has done it since i have owned the car , and now has new coil packs , plugs , filter , ecu and polar chip , FMIC , decat and still does it , just wondered if any one else has/gets this problem sometimes , cheers

 

do you have the dial for the diff flicked forward maybe thats causing it?

It could be a diff problem, is the oil level full in the diff?

 

should of said my car is a 95 wrx ,so I don't have a dial for the diff , all oil was changed in the diff/gearbox a few months ago , another thing if i go round 90' corners at junctions etc, even very slowly the tyre's screech , is this normal for AWD's/imprezas or could it be a diff problem, cheers

 

No, not at all normal. I'd have a close look at what kind of tyres you've got fitted at the front, and also check for bearing wear (jack front of car up, apply steering lock, grab hold of the wheels one at a time very firmly with both hand and literally try to wiggle them).

 

Should have been no need to say as it's under your username under each post.

It does sound like you could have a problem with a seized diff or something but I don't know enough about how they work to say for sure - but I believe the viscous fluid can cook itself under certain conditions (different size tyres or extreme difference in wear of tyres for example) causing it to solidify and act more or less as a locked diff, which would indeed cause tyres to squeel and you would get jumpy/jerky motion when turning, but not when going straight unless wheels or tyre are different size front/back.

 

JDM classic WRX has open front diff, so that couldn't really cause any symptoms specifically when turning.

Any other transmission mechanicals could be suspect though, so would need to be checked.

 

centre diff will be viscous LSD though. that's what I meant - rear might be also.

 

over boost gives a violent jerking under acceleration,i would think you would have it in 3rd and 4rth also as the motor makes more boost in those gears though,have you got a boost gauge fitted? if so what boost are you making when this occurs? could be the solenoid needing a clean,or if you have a bleed valve to up the boost,turn it down slightly.been through problems like this my self,hope this helps bryan

 

it boosts to about 17-18psi , on the polar chip , not sure how accurate the gauge is though , but it doesn't hit boost cut in any other gears , whats it does feels exactly like boost cut and only stop when you let of accelerator , but I don't see how it can boost more in 1st gear than 3r/4th when there's more load on the engine ,
also Ive had a good look over the diff and as far as i can tell they are OK , have jacked car up and turned wheels , i think its more of a case of cheap tyres causing the screeching , the set it has on at the moment came with some new alloys and are called triangle's?
cheers for replies everyone

 

Sounds like diff to me

 

if it IS the diff, changing the gearbox oil won't have any effect as the viscous fluid is separately sealed inside the viscous unit.

That said, if it feels like boost cut then the diff is most likely not the problem.

 

If its got tyre squeal going round corners slowly this to me means the wheels are having problems spinning at different rates which (correct me if i'm wrong) the differential is designed to allow for.Boost has nothing to do with these symptoms.

 

right been out in it again and doesn't always do it , but when it does go all jerky its at around 7000rpm and right when i change form 1st to 2nd gear , its really hard to explain , i don't think it can be fuel cut/over boost , and have ruled out the diff now as far as i can tell - had all 4 wheels of the ground and they definitely not locked together, so not sure what it can be now ? thanks for help

 

jerking at 7000rpm may be the rev limiter kicking in,will be around there anyway