Jump to content


Photo

Aussie 4spd jumping out of 1st once engine warms up.


  • Please log in to reply
9 replies to this topic

#1 RohanLH

RohanLH

    Forum Participant

  • Members
  • PipPip
  • 4 posts
  • Name:Rohan
  • Location:Western Victoria
  • Car:LH Sedan
  • Joined: 04-April 21

Posted 11 April 2021 - 05:28 PM

Hi all, 

I have a query re; recent issues with the 4spd gearbox in my LH that I'm hoping someone can help with.


I've never done much with gearboxes apart from swapping one for another.

When the engine & gearbox are cold it will stay in 1st gear ok and drive & shift as expected.


But once the engine is warmed up to usual running temp the gearbox starts jumping out of 1st gear (violently) 

 

Other gears are fine (can start off in 2nd gear no worries) 


It shifts into 1st (and other gears) ok wether hot or cold.

 

Looking at other posts - Ive checked the shifter rod setup to make sure its shifting into 1st fully - looks ok.

 

The gearbox does seem to have a little noise when running through lower gears, maybe bearings?

 

Ive dropped the gearbox out and removed sideplate. The detent levers don't look very worn (compared to some other pics on here of the detents)

 

Their does seem to be a bit of play in where the shift forks slot into the shift rings (not sure if that's the right terminology - or if thats usual or not?)

 

And the input shaft seems to have more left/right/up/down movement than i thought it should.

 

Gears themselves look ok, cant see any odd wear, chipping or pitting.

Does this sound like bearings are gone? Do you think one of the $250 reco kits you see on ebay (seals, orings, lay shaft, bearings, rollers) would help fix this issue? 

 

Thanks.
 



#2 yel327

yel327

    Oh My, Don't you post alot

  • Members
  • PipPipPipPipPipPipPip
  • 10,835 posts
  • Joined: 10-February 08

Posted 11 April 2021 - 05:41 PM

Sounds like a rebuild kit. Plus maybe 1st gear and the selector plus synchros. You might find the cluster and the main shaft plus input shaft have worn case hardening too.

#3 RohanLH

RohanLH

    Forum Participant

  • Members
  • PipPip
  • 4 posts
  • Name:Rohan
  • Location:Western Victoria
  • Car:LH Sedan
  • Joined: 04-April 21

Posted 11 April 2021 - 10:01 PM

Thanks,   I have a 3spd in the shed too, would the selectors/forks out of that fit the 4spd? Thinking if i'm lucky they might measure up to be in better condition than the current ones.



#4 S pack

S pack

    Scrivet Counter

  • Members
  • PipPipPipPipPipPipPip
  • 13,709 posts
  • Name:Dave
  • Location:Luggage Point
  • Car:73 LJ
  • Joined: 25-January 10

Posted 11 April 2021 - 10:15 PM

Doubt the slipping out of 1st gear is anything to do with the selector forks.

Your box needs a full strip down and replace the worn parts.

I'm leaning towards the 1st and 2nd synchronizer hub & sleeve is the problem and may need replacing.



#5 yel327

yel327

    Oh My, Don't you post alot

  • Members
  • PipPipPipPipPipPipPip
  • 10,835 posts
  • Joined: 10-February 08

Posted 12 April 2021 - 06:26 AM

Not the selector forks, the selector arrangement that engages the synchro rings and the gears, I think Dave has named it correctly above. That bit always wears, along with the teeth that it engages with on 1st and 2nd gears. Plus you always find that the case hardening on the cluster gear, inside the clutch gear and sometimes on the nose of the main shaft is shagged.

#6 rodomo

rodomo

    To advertise here, call 13TORANA

  • Members
  • PipPipPipPipPipPipPip
  • 17,543 posts
  • Name:R - O - B Dammit!
  • Location:Way out west of Melbourne Awstraylya
  • Joined: 10-December 05

Posted 12 April 2021 - 10:53 PM

You need to make a longer gearstick so you have more leverage to hold it in gear.



#7 rodomo

rodomo

    To advertise here, call 13TORANA

  • Members
  • PipPipPipPipPipPipPip
  • 17,543 posts
  • Name:R - O - B Dammit!
  • Location:Way out west of Melbourne Awstraylya
  • Joined: 10-December 05

Posted 12 April 2021 - 10:57 PM

Seriously?

These blokes are on it. It will be be the hub or 1st gear dog teeth on the main shaft.

Once they start to jump out of gear a few times under load it's time for new parts.

 

Good luck



#8 RohanLH

RohanLH

    Forum Participant

  • Members
  • PipPip
  • 4 posts
  • Name:Rohan
  • Location:Western Victoria
  • Car:LH Sedan
  • Joined: 04-April 21

Posted 13 April 2021 - 12:18 AM


Thanks everyone, 

Keen to have a go at it myself so will order a rebuild kit and syncro rings etc & take my time :)

For Hub and Sleeve, could i potentially use the ones out of a spare 3spd box i have? (are they the same?) - and that's if they are actually in better condition.
 



#9 S pack

S pack

    Scrivet Counter

  • Members
  • PipPipPipPipPipPipPip
  • 13,709 posts
  • Name:Dave
  • Location:Luggage Point
  • Car:73 LJ
  • Joined: 25-January 10

Posted 13 April 2021 - 07:07 AM

Unfortunately the 3spd 1st/rev synchronizer hub and sleeve are different to the 4spd. You would need to rob them from another aussie M20, M21 or M22.

Edited by S pack, 13 April 2021 - 07:07 AM.


#10 yel327

yel327

    Oh My, Don't you post alot

  • Members
  • PipPipPipPipPipPipPip
  • 10,835 posts
  • Joined: 10-February 08

Posted 13 April 2021 - 07:45 AM

Pull it apart first. They are a simple box, but can be tedious putting back together, all those needle rollers, spacers and thrust washers are a pain in such a little box with not a lot of fingers room. Once you done one and then do a Muncie, there is so much more room to move!
Best tips, tub of Vaseline or similar consistency grease. And use your old lay shaft to use to setup the cluster needle rollers. Buy the best lay shaft money can buy.
Just about every box I ever pulled down needed: cluster, lay shaft, 1st gear, 2 synchros and first-second selector hub. Plus small parts kit. Every second box would also need 2nd gear, an input shaft and the main shaft too.
If you need lots of parts keep an eye out at swap meets, you can still pick up 6cyl boxes cheap.

Edited by yel327, 13 April 2021 - 07:46 AM.





0 user(s) are reading this topic

0 members, 0 guests, 0 anonymous users