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4th and 5th crunch

otto

By otto,
in General Automotive Discussion

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otto Collaborator

otto

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Posted

When shifting at high revs (above 5500) into 4th my gearbox goes into gear ok but gives out a crunching noise reguardless of how quick/slow i try to shift does it in 5th a little aswell. if im driving around normally the box is smooth as. Has anyone else had this problem or know what it is? My gearbox also has a faint whinning noise when in neutral that goes away when i push the clutch in. thanks:(

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https://www.sau.com.au/forums/topic/23795-4th-and-5th-crunch/
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AndyMac Experienced

AndyMac

Posted
Posted

Try some Nulon in your box as well.

The crunch is from worn synchros usually (sometimes excess wear can be caused by reckless shifting and leaning on the gearstick while driving...especailly 4th and 5th gear {you use these gears to cruise in offen.}).

The whining noise is more then likely the input thrust bearing, and is common in R33 Skylines.

Al Grand Master

Al

Posted
Posted

I honestly found that "readline" made it worse. Never had the problem b4. On the last service i decided to put all the "top shelf" fluids in my car, to give maximum protection, and now at high speed/revs 5th crunches. Never did it with the previous oil, seriously thinking of draining the fluid out and going back to what worked for my car. Not sure of the brand name though :), but my mechanic knows.

Guest RedLineGTR

Guest RedLineGTR

Posted
Posted

it varies from people to people...some people have used it and found no decent results..some have had geat results...when i put the stuff in my mates car it took and decent drive for everything to make a difference about 50-100Km so depends on driving and condition of the gearbox

otto Collaborator

otto

Posted
  • Author
Posted

thanks guys ill give the redline stuff a try, also i took the car for a spin tonight and it didnt seem that bad at first but the more i thrashed the car around the worse the crunch (the problem is only when shifting into 4th up or down, ocasionally 5th) became. In the end even in low revs it still gave a little crunch. i eventually out of despiration decided to double clutch it into 4th and whala the problem was solved changes were smooth again. Does this still mean the problem is with the sincro's or is it a clutch problem??

Duncan Grand Master

Duncan

Posted
Posted

otto, if double clutching (correctly) fixes the problem then it is synchros. the double clutching means the synchros dont have to work coz the next gear should already be at the correct revs.

Nothing wrong with double clutching all the time tho.

I have this problem (worn synchros) in my box and redline has fixed it fine except when I am really hurrying 4->5th.

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