Gearbox popping out of 4th gear

[Anonymous]

This week the MR2 has thrown up another little gem to keep me on my toes.

The gearbox consistently moves from 4th to neutral when under load (it's a manual). It only happens if you put your foot flat to the floor quickly or at around 65mph if you let the speed build (and only in 4th gear). It doesn't make any odd noises just pings out and the revs shoot skywards making me look like a muppet  s:roll: :roll: s:roll:  .


Has anyone else encountered anything similar or fancy guessing what it might be? I'm due a 60k service very soon so I'll probably drive round it until then as the other car is out of action as well at the moment. Great timing!

thanks

dave.

[GSB]

One of 2 things come to mind....

1/ The dogs on 4th gear are worn out, making it disengage. Could happen, but its more usual on lower gears... Expensive repair.

2/ The shifter cables need adjusting.

Either way, sort it out now, as if it is the cables, and you keep driving it like this, you'll end up with problem No.1...

[GSB]

I've just a had a look in the worshop manual and it lists the following possibilities as causes of your problem. They are listed in order of liklihood that they are responsible;

1/ Locking Ball Spring (Damaged)
2/ Gearshift Fork (Worn)
3/ Gear (Worn or Damaged)
4/ Bearing (Worn or Damaged)

The bad news is that all these parts are internal to the box. Continued driving will make the problem worse (i.e. more expensive).

[Anonymous]

Normally the release bearings !

these normally ware and when noticable the gears pop out could happen on any gear but your choices to be 4th!

not to expensive and should only take a day to sort out!

[Anonymous]

Whenever i've come across this it is the selector spring. It's basically a spring which pushes on a ball bearing that goes into a groove that's in the selector rod.

This spring and ball is shared with other gears so i'd doubt it is this, unless it does jump out of other gears. I'd say it's something to do with the linkage and the gear isn't totally being engaged, so it's popping out.

Good luck

[SteveJ]

Normally the release bearings !

these normally ware and when noticable the gears pop out could happen on any gear but your choices to be 4th!

not to expensive and should only take a day to sort out!

The release bearing would only cause trouble with selecting gears as the clutch would be dragging, resulting in the car jumping out of gear immeadiately you release the clutch pedal as the gear hadn't been selected properly.

The problem dave is experiencing is most definately an internal fault with the gearbox, although as to what I couldnt say for certain without taking it to bits.

[Tem]

Since we have the same box as Mk1 MR2, which used to suffer from 4/5th gear popout...just might be the same issue.

From old MR2 list by John Welch:

Having rebuilt several C-50/C-52's I think I have a pretty good idea what causes the 5th gear pop-out problem, and how to fix it.

The majority of the problem is the drivers habits, and improper lubrication.

The design on the "C" series of trannys requires that the fluid be kept at the proper level, and be in good condition.  It does not have a "pump" to circulate the fluid, it relies upon the movement of the gears in a bath to move the fluid throughout the trans case.

The use of a good quality fluid that is replaced every 20K miles should be considered "standard" for this trans.  I use Redline MTL-90 and am VERY happy with it.  You may have good results with other brands, or weights, I'm not here to debate them, but I like the Red Line.

The cause of the pop-out is not the syncros, hubs, or gears....  it's from wear on the main input shaft, and output shaft bearings.   The output shaft is almost submerged in gear oil, the input shaft however is partially out in the open,  This is the one that shows the most wear.

The nature of helical cut gears (used in almost all production manual tran's) is that they run quiet, but the down side is the power that is lost through the axial loads placed on them and the bearings.   Helical gears are constantly exerting a liner load down the length of the shaft that they are running on. This translates into a higher bearing load.

The "movement" of the shifter that you observe when changing throttle inputs is actually a display of the movement of the gear shafts inside the transmission, and play in the bearings.  

The solution is to replace the main bearings, and make sure that the pre load on them is correct when assembling the trans, and use a good lubricant.

[Anonymous]

The use of a good quality fluid that is replaced every 20K miles should be considered "standard" for this trans

so we should be changing the oil in the gearbox every 20k miles then? or do toyota do this in the service?

[Anonymous]

Normally the release bearings !

these normally ware and when noticable the gears pop out could happen on any gear but your choices to be 4th!

not to expensive and should only take a day to sort out!

The release bearing would only cause trouble with selecting gears as the clutch would be dragging, resulting in the car jumping out of gear immeadiately you release the clutch pedal as the gear hadn't been selected properly.

The problem dave is experiencing is most definately an internal fault with the gearbox, although as to what I couldnt say for certain without taking it to bits.

But when my mum took her puma in for the same problem thats what they told her (im know there ford a a pile of poo) but when ever the power was applied to the accelarotr it would pop out. Maybe im wrong just seamed very much like the same thing   s:wink: :wink: s:wink:  , but it's true to say that the gearbox has loads of things that could go wrong so it could be a lot of things   s:lol: :lol: s:lol:

[Tem]

The use of a good quality fluid that is replaced every 20K miles should be considered "standard" for this trans

so we should be changing the oil in the gearbox every 20k miles then? or do toyota do this in the service?

I don't think Toyota does that at all. They only check the oil level in there according to local maintenance chart  s:? :? s:?

I recommend getting rid of the stock stuff at least after 20k miles and putting Redline in. That stuff is good enough for the next 200k miles  s8) s8)

[Anonymous]

Tem wrote:

Since we have the same box as Mk1 MR2, which used to suffer from 4/5th gear popout...just might be the same issue.

Do we?!!!!  s:shock: :shock: s:shock:    s:shock: :shock: s:shock:    s:shock: :shock: s:shock:   Blimey! That I DIDN'T know!!!

Strange how it feels that much different. And I would hope that with the well documented 4/5th gear pop out on the Mk1, they would have sorted this to go onto a much newer car. If they haven't, what on EARTH have Toyota been doing for the last 14 years!  s:shock: :shock: s:shock:

[Anonymous]

thanks for the replies folks,

It does seem to be only doing it when driven hard, you can drive it normally and never notice any problems (my wife couldn't tell).

I'll let Toyota have a play (and laugh at the quote to fix it!). Hopefully it is linkage related rather than something within the box itself!

It has been driven pretty hard though so I fear the worst!

dave.

[Anonymous]

where is the plug to drain the gearbox then?

[Tem]

where is the plug to drain the gearbox then?

On the bottom of the box  s;) s;)

More seriously, check this article:
 m http://spydermagazine.com/2002/Nov/tran ... ansoil.htm m