Jump to content

1st gear and reverse grinding... diagnosis please.

Recommended Posts

EDIT... I originally thought it was a half shaft failure... turns out it is gearbox related.  Grinding in 1st gear and reverse with very little drive.  2nd/ 3rd / 4th all ok with or without o/d. Looking for diagnosis while I start the process of removing the box and engine... at least this will give me a chance to fix that oil leak and a few other things.

Original post:
What a shame - just after thinking how well the car was driving and looking (and also consciously thinking how risky it was to be having such thoughts), a half shaft decided enough was enough... at least I hope it was the half shaft!

I think I was partly to blame... or fully to blame... I forgot the handbrake was on and then when I took off from the lights, the car pulled away for a split second and then something went pop!  I'm trying to re-assure myself that the half shaft should be able to take that sort of load, and so was probably going to break eventually anyway... not sure if that is true or not. 

Anyway - time to get hands dirty and confirm what's what.

Two photos attached are the start of the day, full of promise, and the situation about 1hr later!








Edited by bigmalcy
Link to post
Share on other sites

Well it looks like I jumped the gun... 

Both half shafts are ok...

With car jacked up at rear and engine running she crunches and grinds like the proverbial in 1st and also in reverse. 2nd/ 3rd / 4th with and without o/d all spin the rear wheels without any accompanying noise so I am hoping that that discounts any o/d issues.

Engine and box definitely coming out... presume the fact that it's reverse and 1st only may be a clue as to the cause?  What is the common link (I know next to nothing about these boxes).


Link to post
Share on other sites
  • bigmalcy changed the title to 1st gear and reverse grinding... diagnosis please.

I should really do some reading before turning to you lot... 

Based on my trusty Moss catalogue, it looks like reverse gear may operate through the 1st gear cog on the output shaft...?  So it looks like I'm probably up for a 1st gear countershaft + reverse gear + 1st gear.

Is now the time to install a later box with 1st gear synchro rather than fix the old one...?


Link to post
Share on other sites

So - now I'm researching options for fitting an all synchro box.  

I've found the following box on the bay, but keen to understand what I need to consider... 

e.g. can I easily fit my top cover with o/d switches and selectors etc to this box? 

Is swapping the o/d unit over from my box to a non-o/d box straightforward?

What other Triumph boxes can I use... 2000, GT6, etc?

Which boxes require an adaptor for the rear mounting?

TIA for your advice!


Link to post
Share on other sites

I'm making a bit of an assumption that you have an original A type O/D on your current box?

In answer to the first question, I can't see why it wouldn't be a straight swap for the top cover & if you did encounter any issues it's no great issue to drill & tap those raised plinths on the non O/D box to provide the correct locations for the overdrive inhibitor switches & a reverse light switch while you're about it.

As for swapping them over - no, it's not straight forward as you have to strip both boxes & transfer the shorter output shaft from the O/D box to the new all synchro box...certainly do-able & I've done several but not for the feint hearted.

As for other boxes - a lot can be adapted, the common ones being the stag, Triumph 2000 & 2500, I don't know anything about the GT6 box & suspect it's not compatible.

Link to post
Share on other sites

Hi guys

Thanks for all the responses... I think I've found a suitable  4-synchro box here in Aus with J type o/d. Based on prices of spares I reckon that's the path I will go down.

Can anyone confirm that the gear ratios in the later boxes are the same as the original box with A type overdrive?

Thanks again for your inputs!


Edited by bigmalcy
Link to post
Share on other sites

Join the conversation

You can post now and register later. If you have an account, sign in now to post with your account.

Reply to this topic...

×   Pasted as rich text.   Restore formatting

  Only 75 emoji are allowed.

×   Your link has been automatically embedded.   Display as a link instead

×   Your previous content has been restored.   Clear editor

×   You cannot paste images directly. Upload or insert images from URL.

  • Create New...

Important Information

Please familiarise yourself with our Terms and Conditions. By using this site, you agree to the following: Terms of Use.