gearbox crunching at high revs

[scope]

hey,

i'm posting on behalf of a friend.

he has an ae92 corolla (1989 i think) and whenever he changes into second at high revs (happens changing down and up) it will crunch like there is something in the way of it going into gear. why does this happen and why only at high revs?

thanks

[Dr-X]

Worn synchros, it'll need a rebuild (or you can just live with it). There are a few band aid solutions - try a nice thick new gbox fluid.

[gordon77]

try a nice thick new gbox fluid.

my car does this also but in 3rd only after replacing the factory oil with 75w-90. what would be a good oil to replace it with again with to prolong the inevitable

[ee904age]

Cant go wrong with 85w140 truck diff oil

Edit: dont take this seriously

[rolla_fxgt]

Isnt it just a standard toyota gearbox fault? Everyone i know seems to of had this problem in a toyota of 1 sort or another over the years.

I even managed to "help" my mum's corona into aquiring this problem when the fxgt was of the road.

My fxgt's been doing it for almost 4 years now & it still goes, i just treat it gently on cold days or when the engines cold & it seems ok.

& besides syncros are expensive to replace & then u find all sorts of other lovely stuff that could do with replacing while u have the box out & open. & then it turns into a hey lets mod the whole car & make it go faster & put in a stronger clutch & replace anything you can think of.

Just treat it gently & all should be ok.

[solberg Fan]

... & then u find all sorts of other lovely stuff that could do with replacing while u have the box out & open.

so true... dam gremlins

[ChaosAD]

Common fault from the years of thrashings.
Try auto gearbox fluid (dexron III?)
Or rebuild.

Dunno why, but my shortshifter seemed to smoothen my gearbox a bit

[CozmoNz]

arnt syncros like $25 each or something? you pay for the labour more than parts.

Warwick, how much for syncros!

[ChaosAD]

And can you change them yourself with just a press and basic tools?

[rolla_fxgt]

Yeah fair enough syncro's are cheapish, but once u get all 5 or however many it is, it adds up & if u find other damage inside then it gets really expensive.

If a gear has to many teeth missing its normally cheaper to get a new box aye. & upgrade to something like a gtz box with the stronger gears in it.

[Bazda]

Yeah fair enough syncro's are cheapish, but once u get all 5 or however many it is, it adds up & if u find other damage inside then it gets really expensive.

If a gear has to many teeth missing its normally cheaper to get a new box aye. & upgrade to something like a gtz box with the stronger gears in it.

gtz box wont fit, unless you buy the drive shafts as well, also the main gear coming off the eng is a diff size so that will also need to be changed.

use dextron III, worked a charm in my old g/box

[gordon77]

use dextron III, worked a charm in my old g/box

i talked to a mechanic today about what oil to use. i put 75-90 in mine, it started graunching into 3rd (never did before i changer oil). he told me that i shuold use dextron 3. reason being is because it is a lighter oil it doesnt take the syncros as long to spin up as they would in a thicker oil

[Bazda]

use dextron III, worked a charm in my old g/box

i talked to a mechanic today about what oil to use. i put 75-90 in mine, it started graunching into 3rd (never did before i changer oil). he told me that i shuold use dextron 3. reason being is because it is a lighter oil it doesnt take the syncros as long to spin up as they would in a thicker oil

yea thats right, it gives the syncro more friction. The cones need to puch the oil out faster so it can grab better, thats why atuo trans is good to help with this (very thin oil)

[boy_with_a_new_toy]

just did a gbox job for a mate, spunds like ya synchros are worn, no prob just treat her gently, cost of a box is prob 400 without a rebuild, so i suggest u b careful and freserve yours. thell go for thousands of km's with a slight graunch before they shit out completely.

[shaggz]

i had the gear bos rebuilt it cost my my arm and my leg almost literally had to sell them to pay for it your mate is putting the clutch in ah?......................................