Stripped gear... x 2

Hi guys.

I have 2 gearboxes that I have bought as part of my budget build. Both have a similar issue.

One has a stripped 4th, and another a stripped 3rd.


Now I only have the stripped 4th gearbox open. The other I haven't investigated. My question is can I just buy a 4th gear and also a 3rd gear etc? I presume I can? Reason being is I 'can' make 1 good box out of the two, but ideally I wanted to fix both so I have a good box and then a spare too.

This is the scenario:-







Now gearboxes are the 1 thing on a car I know very little about, a local friend will be doing the repairs for me but I just wanted to pre-empt the repairs if any of you guys can help. The car will only be running just over standard power and this build is unfortunately on a budget so quaifes etc are well out of the question.

I did have someone who apparently had lots of gearbox spares, but apparently overnight he now doesn't... lol so on the hunt.


I just wanted to clarify and get you guys advice.


Thanks chaps.

Can't you just strip down the two shafts and use the good gear from one box and rebuild it into the other, so you have one box rebuilt and ready to go.
When you have enough funds, because the 2 gear sets 3rd and 4th, from Nissan are going to cost you a motza.
You might be better off getting another busted box that has blown 1st and 2nd and use the 3rd and 4th gears from them, then you have your 2 boxes and a few spare parts left over.

You would be best off removing the parts from one box ie the damaged 3rd, then using the matching 3rd gears from the other box or visa versa with the damaged 4th in the other box
if they are good make sure you renew the bearings also
check the outer wrasse's of both main and input shaft end case bearings to make sure they have not spun in the casing
make sure 3rd, 4th hub, synchro is not damaged and sticking
also check the baulk rings for excessive wear
double check 3rd, 4th selector for damage as this is one of the biggest causes of failure in these boxes

New gears will cost you an arm and leg from Mr Nissan (around £450 for a pair 3rd gears) so add the bearing cost onto that and any other parts youll need and can work out very expensive even if a mates doing it for you.

Once hes pulled them apart drop me a message with anything you may need as I have spares in stock but there are some things we are short of too, I should however have a pair of matching 4ths and few other bits you may need but cant do these as a freebie unfortunately Ross as gearbox parts are quite sought after now.

That's no problem at all bob, again thanks for the advice.

By the sounds of it from you guys I am indeed better off making a franken-box out of these two to get me going.

Cheers guys.

Make a good box out of the two and then sell the casing and other internals to help fund something else?

rebuild whichever box looks to have best condition gear teeth, with all the debris that come off stripped gears it needs good checking for damage .

I would echoe Mr B's words about checking for debris damage.
If any debris went through the other meshes under load, they might have overloaded some teeth beyond their static and/or fatigue limit which would weaken them.
Any gear is only as strong as its weakest tooth.
I design and analyse the gears that go into Cummins engines in Daventry and if we get a gear failure like this during test, the whole geartrain is scrapped because it would be high risk to reuse any.
If you do re-use the gears i would check them for any signs of scoring up the flanks, chips at the tips and more importantly cracks in the tooth roots. Initial crack propagation may not be visible unless you use die penetrant.

Sorry to hijack the thread but would getting the gears shotpeened be of any advantage?

^ It would if gears in good enough order to warrant the work/cost . needs be done by experienced professionals as peening gears correctly is very very skilled in equipment & operator .

Intresting job cosmic .... had a quick look up of the company i didnt realise they do such a wide variety ....

Does sound cool job, any staff in house services useful to your gtir build or gtir development in general ...

I love the job, the tech center is on 3 floors and borders the production plant,
We also have gage labs, test cells, metallurgy, test rigs.
Its great because you have experts in every field on tap to help.
Gage labs is cool because we have state of the art CMM that inspect parts almost to a micron,
We do massive engines at Daventry, the ones that go into the largest mining vehicles;
http://www.vannattabros.com/adospics/kmsutrk.jpg

Regarding shot peening, we specify this on some critical crank gears.
it adds beneficial compressive stress to the gear root so when the teeth bend under load the tensile stress generated at the root is cancelled out. However if a crack is already there it wont heal it, it'll always be a weak spot.

Also like Mr B says, its a skilled job and the Shot size, arc length, intensity etc are kept secret. We use MIC and we simply spec their shot peen code on our drawing with the target compressive stress becuase they will not divulge anything else. How they achieve it is a mystery, but we know they do.
If its not done properly all you have is shot blasted gear, not peened.

By the way MR B, are you a mechanical engineer? You know your stuff.

He is only 10%  human ... the rest is made up with  dark matter and state of the art electronics .....
All that sounds way beyond my tiny brain cell however i still find it very intresting and always like to try and understand the in's and out's of it all ....

lol
On a good day I am .
It's good to love your job, sounds cool place with some useful in house services for your gtir lol .

Some say that he sleeps with car books under his pillow and data logit plugged into his nipples at night

Ha ha, you're lucky i communicated with writing, usually its morse code..-..-..---..-..--.

Stu wrote:Some say that he sleeps with car books under his pillow and data logit plugged into his nipples at night

All we know is he is called Mr B or due to his location should that be ladybB

^^^ hahaha

I had some part supplier catalogues stacked up in bed other night, the wife not pleased, she was all lady last time I checked but I don't service/maintain her much these days lol .

Hahaha you don't dip you stick to check the level much? Hahaaa

As long as she runs quietly I leave it be. If get noisy I may give her a squirt of lubricant