915 vs 901 vs boxsterS - Opinions needed., pros/cons, difficulty moving to, etc... |
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915 vs 901 vs boxsterS - Opinions needed., pros/cons, difficulty moving to, etc... |
naro914 |
Jan 11 2012, 12:07 PM
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#21
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Losing my mind... Group: Members Posts: 2,476 Joined: 26-May 06 From: Charlotte, NC Member No.: 6,073 Region Association: South East States |
I'd like some opinions from the general peanut gallery. Is it worth the cost go to a 915 transmission over a 901? What is the benefit, if any? And, what's involved?
How about a Boxster S transmission? I've heard stories that a 915 is a pain to install, and doesn't every really shift well. I can't comment since I've never driven a 915 in a 914. But, with the bigger engine we now have, is it something I should be considering in the future? Being that I can get a complete 901 for cheap, and already own 3.... I know nothing about the Boxster S trans, other than a 6 speed with cable shifting would be very nice. thoughts, comments discussion? thanks |
pcar916 |
Jan 11 2012, 03:10 PM
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#22
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Is that a Lola? Group: Members Posts: 1,523 Joined: 2-June 05 From: Little Rock, AR Member No.: 4,188 Region Association: None |
initial cost for a 915 conversion is simply more $ (IMG:style_emoticons/default/beerchug.gif)
I have yet to install a 915 because the 914 seems very hard to kill. But I just broke a pinion gear on the 914 trans recently so I'm building both. 915's can be good shifters too. But they both have the Porsche style synchronizers so neither will be super fast to shift. Built and maintained properly the 915 will shift almost as well and will handle more torque. A few thoughts. 1. The 915 ring and pinion gears are much larger and the ring has a bit longer lever arm from the mesh to the axis. Easier on both R&P. But to get the same ratio as our 914 boxes (7:31) you have to find an early (or custom) 915 R&P. Later ones are 8:31 so the gearing is much different. 2. Shifting them with either the 916 side-shifter style or the Wevo conversion is expensive. Fab'ing a cable shifter is less expensive, but more effort. There are some ready-made cable shifting systems out there. 3. Up above 250hp you should consider cooling/filtering the oil in either box unless you drive real slow, or live in super cold weather. 4. A few thoughts on early vs late 915s. - The early mag case version is lighter (mag) has a 7:31 R&P ratio, and uses a mechanical speedo drive. It also has steel inserts in the mag case for the front bearings. The aluminum cases just mount the bearings into the aluminum. Diff carrier bearings are the same for either box. - The mag case 915's use the same differential form factor as the 914 as well as course splines on the output flanges. Later diffs have fine splines and different dimensions on the spigots (reluctor ring for the electronic speedo) and ring flange. Also the late 915's use carrier spacers and shims that are notched for the reluctor ring. Why is all of this important? If you already have an LSD or TBD diff in your 914 it will be useable in an early 915 mag case. 5. The clutches are very different so your flywheel adapters will differ. I'm sure others will chime in on this one as well. |
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