915 Close Ratio Trans With LSD

[Bernie B]

FS: 915 Close Ratio Gearbox. Built a few years back for a project that was never completed.
Zero Hrs. on a 1972 Mag case, new Syncro's & Bearings, 7:31 R&P, GT Torque sensing LSD with the following gears:
1st. AZ 11:35 / 3.18
2nd HX 18:33 / 1.83
3rd NT 23:29 / 1.26
4th QQ 26:26 / 1.0
5th SN 28:23 / .82

SOLD plus shipping & fees. Email is preferred. bbuschen@comcast.net

[Frank Beck]

Bernie,
Technically this would not be considered "close ratio".

Stock 75/76 gears but with 7:31 rather than 8:31 R&P.

What's the brand of TB diff?

Thanks

[Bernie B]

Frank-
By your own example replacing an 8:31 Ring & Pinion with a 7:31 essentially creates a close ratio gearbox. But that’s not how this gearbox was built. It was built to utilizing a 1972 911 Mag case gearbox with a 7:31 Ring & Pinion with a Guard type 914 Torque Sensing LSD (the Guard type 914 LSD is the correct LSD for a 915 with Mechanical speedo drive) stock 1st, 2nd & 3rd gears and then installing a lower ratio 4th & 5th gear set from a 1979 911SC. A few gear charts follow to illustrate the build results. The first spread sheet and chart are a stock 72' 915 gearbox and the 2nd set are the current close ratio set-up.

[914-6gt]

I'm a subscriber-- you couldn't build it for the asking price...

[Frank Beck]

Bernie,
My only point is that it's the same gearing as a 915/44 except with 7:31 R&P; no actual expensive race ratios used. If one were to buy a '75 gearbox and install a 7:31 R&P they would basically have your transmission... except with a mainshaft seal that was accessible from the outside of the box.

If one were to build an LSD box using 2nd-5th special ratios (brand new gear sets) and 8:31 they would have a $9-10k box.

Also I would humbly challenge that a torque biasing diff is a true limited slip. They work differently and one has advantages over the other in certain applications.

Good luck with the sale.

[sithot]

Good deal any way you cut it.

My early early '74 has a 7:31 in it which is apparent as soon as you punch the "loud" button. (gas pedal) 1st is a short trip but 2nd 3rd and 4th are fun! Car has a much modified 2.7RS spec. engine. Plenty for a relatively light car. The '74's were still pretty light. 25kgs (55lbs.) more than a '72-'73.
Tony Lapine did a good job.

I'd really like to shorten my '80 box. Cheap horsepower. (sort of)

[Bernie B]

Sithot-

Thanks for guiding this post back on topic. For a while there it looked like I was hosting a debate over the use and terminology of “close Ratio” and now “Limited Slip”, kind of waiting for the punctuation and grammar police to chime in next. The good news is this close ratio gearbox is now sold with a back-up, so we can now lay this thread to rest...

[Frank Beck]

The good news is this close ratio gearbox is now sold

Bada bing, bada boom. That's great Bernie.

I have a low hour 915 GT torque biasing diff that I would gladly trade for a ZF if anyone is interested.