1302 IRS Gearbox with 150hp Turbo Engine

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KJD 1302s
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1302 IRS Gearbox with 150hp Turbo Engine

Post by KJD 1302s » Wed Jan 14, 2015 3:50 pm

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 :D 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

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davidt
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Re: 1302 IRS Gearbox with 150hp Turbo Engine

Post by davidt » Mon Aug 27, 2018 4:24 am

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

Bruce2
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Re: 1302 IRS Gearbox with 150hp Turbo Engine

Post by Bruce2 » Tue Aug 28, 2018 1:42 am

davidt wrote:
Mon Aug 27, 2018 4:24 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.

Casting Timmy
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Re: 1302 IRS Gearbox with 150hp Turbo Engine

Post by Casting Timmy » Thu Aug 30, 2018 6:49 am

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.

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Pablo2
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Re: 1302 IRS Gearbox with 150hp Turbo Engine

Post by Pablo2 » Thu Aug 30, 2018 7:03 pm

Casting Timmy wrote:
Thu Aug 30, 2018 6:49 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.
aka Pablo, gears, Geary
9.36 @ 146 in '86

Casting Timmy
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Re: 1302 IRS Gearbox with 150hp Turbo Engine

Post by Casting Timmy » Sat Sep 01, 2018 4:12 pm

Very cool Gears.

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Pablo2
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Re: 1302 IRS Gearbox with 150hp Turbo Engine

Post by Pablo2 » Mon Sep 03, 2018 10:13 pm

All the same ratio, F1 tooth profile in the back, OE style 094 teeth in the front, strong but quiet-running street tooth profile in the middle

Image
aka Pablo, gears, Geary
9.36 @ 146 in '86

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