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R33 Gearbox Wont Change Under High Rpm No Crunch?

xm4tr1x
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xm4tr1x Enthusiast

xm4tr1x

Posted
Posted

Hi guys, I've had this problem for a while now and its really bugging me, mechanics are telling me its syncros, others say clutch.

I'd like to hear what the experts on SAU have to say about it, before you ask I've searched threads and couldn't find anything that describes what I'm experiencing.

OK so once i start i let it warm up a few min before engaging gear, for the first 3 min of driving its great gears change with ease no problems, as it gets warmer it gets harder and harder to change gears, more so under higher RPM, the gear stick just doesn't want to go into gear, it feels like im hitting a wall! i feel like i can break it trying to do so. lol. I've tried wriggling it into gear, double clutching, nothing works i just have to wait for the RPM to drop to <3k rpm before it decides to go into gear, there's no crunching or grinding. I've tried adjusting the friction point on the pedal.still nothing. What the hell? stationary it goes into every gear. low RPM it goes in to every gear. even down gearing at high rpm wont work.

What are your thoughts?

Much appreciated.

some details about the car:

r33 det series 2

110k

jim berry clutch

original gearbox

shimmed diff.

MrStabby Grand Master

MrStabby

Posted
Posted

Wont be clutch, because its fine cold and you've been playing with the friction point. (FWIW If the friction point is too low then the clutch might not be fully disengaging and that will make changing gears difficult).

Have you got newish, synthetic oil of the correct viscosity up to the fill mark? If not, i'd be starting there.

SiR_RB Grand Master

SiR_RB

Posted
Posted

I had an issue like this at the drags last month

Without a burnout no problems at all....after a burnout wouldn't go into 2nd, no grinding or anything just couldn't find home

Don't know what it is so I'm curious to see what ppl say

89CAL Grand Master

89CAL

Posted
Posted

OP: As with what some of the others have suggested, you need to list what oil you are using. To me it sounds like the oil you are using becomes to thin as it warms up. I would suggest changing oil if there is no problem while the gearbox is cold and then gets worse as it warms up

pol1on1 Mentor

pol1on1

Posted
Posted

Sounds like synchro 1st start at changing the oil it's the cheapest option and you can go higher in number if you think the internals are a bit worn out

Say the normal is 75W 90

A higher one is 85W 140

Do a flush so it nice and clean and not metal fragments in their and use a good brand like royal purple.

Tell us what you did to fix ?

pol1on1 Mentor

pol1on1

Posted
Posted (edited)

Also oil basics

The W stands for winter it's the viscosity when cool so 75 is thinner than 85 but you got no problem there because you have problems with the second number (viscosity when HOT) the 90 this could be old oil and losts it property's or the previous owner was using 140 then when you get service done it's back at 90 also worn internals will need thicker.

Hope it helps you.

Edited by pol1on1
jiffo Mentor

jiffo

Posted
Posted

As you've pretty well ruled out the clutch, I'm thinking it's a worn box.

The k's quoted may not be true so try a test and report back.

Drive the car in 2nd and hold the stick hard into gear. Accelerate/back off a few times and feel how much the stick moves against your hand.

Do this in 3rd, difficult trying 1st as the car accelerates too quickly but give it a try.

With a worn box, you get excess end float in the main shaft. You'll feel this through the stick as the shaft tries to move forwards/backwards due to the thrust from the helical gears.

You can reach a stage where the shaft moves too far and even though the synchro has worked, the result is tooth on tooth so you simply can't select the gear.

You may find selecting 2nd is a no-go and 3rd is OK but with a crunch.

(2nd has gone tooth-on-tooth while 3rd has moved too far away for correct synchronisation)

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