Checking over a gearbox

[Johnwahlberg]

Hi. I have a single rail j type overdrive gearbox that is out a scrapped car and my plan is to change over my non overdrive. I have all the parts required, propshaft etc. can anyone Advise on what checks I can do to the gearbox prior to putting it in and trying.

it seems to go through the gears ok, but in any gear between the input drive and output, there is slight play, about 3mm, is this normal.

The propshaft also has a few mm play on the flexible joint, the joint that’s behind the rubber seal

any advice on what to look for and the conversion would be much appreciated, I’m no mechanic, but not a complete novice.

many thanks in advance for any advice

john

[glang]

Hi John, not sure what you mean by 3mm play. Is that up and down in the ends of the shafts or rotational backlash? There will always be a bit of both in all gears except 4th which will reduce the play especially rotational. It's difficult to assess a gearbox without either using it or stripping it so I would listen to the bearings when turning it by hand, replace the front and rear oil seals which is quite easy, check all bolts are tight and then install it. It could have poor gear changing due to worn synchros or jump out of gear so be prepared to have to remove it again.....

[Dannyb]

You could take off the top cover and check the gears for worn/broken teeth etc. But I would just do as John says above and see how it goes. Also you say this one has an overdrive fitted so you will need to see if that works OK at the same time.

 

Danny

[Johnwahlberg]

Quoted from glang-

Hi John, not sure what you mean by 3mm play. Is that up and down in the ends of the shafts or rotational backlash? There will always be a bit of both in all gears except 4th which will reduce the play especially rotational. It's difficult to assess a gearbox without either using it or stripping it so I would listen to the bearings when turning it by hand, replace the front and rear oil seals which is quite easy, check all bolts are tight and then install it. It could have poor gear changing due to worn synchros or jump out of gear so be prepared to have to remove it again.....

 

[Johnwahlberg]

Quoted from glang-

Hi John, not sure what you mean by 3mm play. Is that up and down in the ends of the shafts or rotational backlash? There will always be a bit of both in all gears except 4th which will reduce the play especially rotational. It's difficult to assess a gearbox without either using it or stripping it so I would listen to the bearings when turning it by hand, replace the front and rear oil seals which is quite easy, check all bolts are tight and then install it. It could have poor gear changing due to worn synchros or jump out of gear so be prepared to have to remove it again.....

 

[Johnwahlberg]

Hi, sorry for the late reply, been on away on holiday, yes it’s backlash play,

thanks for the advice it’s appreciated, had the top of and all looks ok, so will change the seals and give it a go, hopefully in the next few weeks. Will post my result.

thanks again

 

[glang]

Fingers crossed your lucky! 3mm backlash is no problem, the single rail gearbox was the strongest version and in a Spitfire should last well....