Hi,
I have a stock 1302s IRS gearbox currently fitted to my Beetle and in July the plan is to fit a 1600 turbo engine ~150hp, I am going to add a central gearbox mount and the rear tyres are 185/75/15 road tyres so not massively wide. What components need to be upgraded before I blow it to pieces side plates, diff, cv's?
Any help/advice would be much appreciated.
My gearbox is the same as this one http://s59.photobucket.com/user/SXTrail ... 8.jpg.html
Just killed my 1972 1302 box. I run an injected/intercooled 1915 Scat engine running 13psi boost. Runs around 170-180hp at the flywheel. Makes boost from around 2500rpm in top gear and pulls really hard from 120-170kph. So 4th gear died going uphill on the weekend. Just makes a very loud grinding noise and has no drive. The other gears work fine. Too much torque me thinks. I am going to replace my gearbox with either a 73 or 74 single side cover gearbox from 1303's as I have a version of both in my shed. I will be changing the side cover to a H/Duty version as well to stop the crown wheel from moving sideways in the case.
Hooroo
David
davidt wrote: ↑Mon Aug 27, 2018 2:24 am
...........Just makes a very loud grinding noise and has no drive.
Fine tooth gears. When you start slamming the gears, the small bits of steel that you chip off of the slider's engagement teeth, or the synchro cone's teeth get caught between the fine teeth of 3rd or 4th, causing them to chip off. The more chips floating around, the more teeth that chip off. Until the whole gear lets go.
Your two single side cover gearboxes have the same fine tooth gears. Replace them with the gears from a 72-75 Bus 'box, they're coarse tooth gears and they don't break.
I do hope that you open up the old box, I have seen some just taken out with the heat of thrust loads as well.
I've seen some fine tooth boxes with a lot of scuffing from super old gear oil and high loads. Eventually the idler bearings being melted and then the thrust washer gave out along with melting the main shaft bearing in the gear carrier.
I do think that the fine tooth gears (same cut as the 091 which just had a wider gear) are stronger than people give them credit for. I really wish we could get some "medium cut" gears in the better materials for 3rd and 4th, spread the compromise between efficiency and strength like the factory did with the later 091 3rd's.
I'd really be best to switch to the bus gears like Bruce mentioned, probably add some other items as well. He makes a great thrust plate for the mainshaft bearing, but also add steel caged single spaced idler bearings at a minimum. A lot of the other common upgrades can be used as well, you might even think about the early swing thrust washer for the pinion bearing being added to the later box. (Pocket first for washer, shorten race, and put in shorter bearing) You can throw in an 091 idler as well on first, just contact Folts and let him know what you're building and he will modify the 091 idler for a T1 and the thrust washer at the same time. It will require n 091 1-2 slider and synchro to finish out the conversion.
I've also been thinking about testing out pinning the 002 beetle gears as the braze has been noted to break free by some. My thought would be drilling in from the outside and putting in a pin and tacking in place with a TIG.
Casting Timmy wrote: ↑Thu Aug 30, 2018 4:49 am
.. I really wish we could get some "medium cut" gears in the better materials for 3rd and 4th, spread the compromise between efficiency and strength like the factory did with the later 091 3rd's. ...
I recently did just that with our 094 gears. Most our 4ths now have a higher tooth count than our big tooth race gears, making them quiet (for highway cruising), yet stronger than OEM.
Update on my gearbox failure. I have been running synthetic oil for the last 6 years. So after removing the transmission I drained it expecting to see a lot of metal come out. Nothing. Oil was clean-as.
So does that mean that 4th gear was spinning on its hub?
Is this situation why 3rd/4th gears are welded when performing a performance rebuild?
I guess I should strip this box down one day to see.
Hooroo
My 67 and 68 swing axle just wouldn't shift worth a crap any more after I hit about 15 lbs. boost with my 1679. I sent it to TimsACVW and he welded the 3rd and 4th gear hubs, replaced a main bearing and the reverse gear along with a couple sycros. The main bearing and reverse gear weren't caused by the power....they were just worn from age .
It's been holding 200 plus lb. ft of torque to the wheels so far. Probably 20,000 or more miles on it.
I haven't sent the 68 trans in for a rebuild yet.
Stripped66 wrote:The point wasn't to argue air temps with the current world record holder, but to dispel the claim that the K03 is wrapped up at 150 HP. It's not.
If fourth gear was spinning on it's hub, the hub usually moves forward and it feels locked into fourth gear. I've seen fourth have the following from high loads:
Plastic cage bearing melted and plastic get spun out from under gear
Thrust washer broken and gone
Mainshaft bearing movement and pounded into the nose cone
Depending on year, could be a sheared key
My guess is if third is working you have pushed the mainshaft back far enough the fork doesn't and can't get it to fourth gear anymore. Thrust washer could or could not be there as well, sometimes on the single drain cases the 1-4 gear chunks stay in the front half.
I was surprised when there was no metal in the oil when the box was drained. Just doesn't make sense.
The very loud gear grating noise when the clutch was released (whilst in 4th) makes me expect to see some form of debris.
Hopefully the 1973 single side plate IRS Superbug 1303 gearbox will do a better job than the 1972 double side plate IRS Superbug 1302 gearbox did. I am very easy on gear changes and datalogs show I take 0.8 seconds to shift a gear. But a 1915 fuel injected engine running 13lbs boost and 6000rpm has just a little bit more grunt than the original 1600 did.
20190128_184008.jpg
20190128_144842.jpg
Hooroo for now
David
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side plates, diff, cv's? 
