Hi there,
I have a '91 Grey import GTO twin turbo 5 speed manual. I have had quite a bit of service work carried out on the engine, but have recently noticed a strange noise coming from the engine in 3rd and 4th gear. When gently accelerating in these gears, mainly 4th at about 40mph there is a grating sound which soon goes with a bit more speed. I cant check where its coming from when it is in neutral as it only happens in the middle gears.

Any ideas or has anyone come across this before?

Cheers

K

sounds like it could be a g/box bearing, if its only in 3rd or 4th, does it make the noise at the same speed/revs in 5th? it could be the g/box or the transfer box, you really need it on lift and run the car with someone listening underneath also have you checked the oil levels and any oil leaks on the t/box and g/box

Yes he is correct , lots of these that were 5 speed had an syncro-ring and guide arm issue after a period of time. It would alter result in the meshing ring in the front of the gear to wear down a little. The guide arm that locks between the 2 usually would bend near the end or the shaft , un properlly seating the ring to the gears 3-4 . As teh gear wears down and time later as its in gear the mesging ring that fulkly locks the gear is riding along the worn edge and making a grinding noise , hence the locking area of the ring is spinning out of sync with the engagment gear. Sumtimes a repair can be made , but full dissassembly and parts will be neaded.

Cheers, I will look into that. hopefully get it sorted. not being to mechanically minded and cash being at a minimum at the moment, I assume it will be causing wear on the parts, but will this be causing a lot of damage?

Cheers

Eventually teh synchro and gear will wear down to where it will just pop out when selected into that gear , or not engage at all. It varied , sum guys that drive hard alot it wears down the synchro plate and synchro gear itsels as well as the engagment gear , some cases the synchro selector bends up and minds.