flipping the R & P, How To Options

[statesblue]

Is there anyone out there who knows how to flip the R & P ? Looking for some detail as to how its done. Is there a tech article on the subject ? Any help would be appreciated.

[HCRDAN]

Is there anyone out there who knows how to flip the R & P ? Looking for some detail as to how its done. Is there a tech article on the subject ? Any help would be appreciated.

uh... (IMG:style_emoticons/default/huh.gif) (IMG:style_emoticons/default/confused24.gif) The fact that I have to ask what "R & P" are means I'm unlikely to be able to help, but I'd still like to know what they are...
(IMG:style_emoticons/default/unsure.gif)

[Borderline]

flipping the R & P (ring and pinion gears) is complicated and requires some special tools or a lot of money. The good Doctor may be able to help you.

I won't ask why you want to do this.

[DBCooper]

Usually done to put the 5 speed 901 tailshift transmission into a VW bug. Far stronger solution than a Berg 5 speed conversion for a T1 transmission. Basically it's removal of the gear stack and intermediate plate, flipping the differential to the other side and reassembling.

IF it's going into a bug then there are a lot of other changes needed, most simple, aligning the nose cone with the bug shift rod a little complicated. There used to be a pretty good article on cal-look.com, another in the shoptalkforums.com. Search there for details. If I'm not mistaken there's a German company that sells a nice-looking kit, complete with a new shorter nose-cone, axle flanges, etc., that makes everything very simple.

[Cap'n Krusty]

Or you could use a 901, not a 914 box, and your problems would be solved. Flipping the ring gear virtually requires you have the fixtures, which have been unavailable for decades (and were REALLY expensive when they were available).

The Cap'n

[pcar916]

Have you considered flipping the 914 transmission and converting to a cable shifter? Simpler in my book! The 901, 914, and early mag-case 915 transmissions use the same carrier bearings, shims and LSD/TBD carriers. But as the Captain has said, the R&P's in the 901 (and 915) are already like you want them!

Now, to answer your question...

Which transmission are you talking about and what application (i.e. hp / torque requirements)?

Note: Just flipping the diff won't change the pinion depth. You only need the pinion depth tool (the previously mentioned expensive tool) if you are changing gears with slightly different thicknesses, or installing a new R&P. FYI you can do this without that tool but it takes longer, and you need more trial-and-error shims.

All of this assumes you are familiar and competent with all of the tools to do this. Not just dial calipers, but dial indicators, torque wrenches (both ft-lbs and in-lbs) and the like. It's also good to have at hand lots of pry bars/pullers to get bearings off if you need to. The carrier bearings don't give you much room to work with on the ring side. If you have to replace your bearings, care must be taken not to goober-up the shims and spacers. They can be hard to find.

The side cover on the 914 transmission or the case on the 915 may need relief for the ring bolt heads and the vent tube has to be relocated. I've heard some that grind the bolt heads, but that's not a process I like. It screws up their heat-treatment.

Theoretically, assuming the preload is good already, and if the bearings are good and can be reused (i.e. not removed) then the shims will maintain the offset in the other direction if the carrier is simply flipped. I haven't checked that because I've always started from scratch with new bearings.

I'd not do it without completing the entire procedure. That means checking the preload, backlash, and tooth contact pattern.

The pinion depth would stay the same and the preload would be close, but the carrier shims and intermediate-plate gaskets might need some tweakin' to get the proper contact pattern.

If you install new bearings on the 914 carrier...
The 914 factory manual has the instructions for differential setup but you would have to transpose the ring offset. That said...

The 911 factory manual has the instructions for the 901 and the ring configuration you want, but the preload values are different and you'll want to use those from the 914 manual.

Note: If you flip the transmission... whichever model, then external cooling is advised. They don't have the big oil galleries on the "top" of the cases that exist on the "bottom".

Good luck.

[r_towle]

Or you could use a 901, not a 914 box, and your problems would be solved. Flipping the ring gear virtually requires you have the fixtures, which have been unavailable for decades (and were REALLY expensive when they were available).

The Cap'n

(IMG:style_emoticons/default/agree.gif)

Call EASY in CA. Last time I called he had quite a few of the 901 trannies ready to ship out.

Its alot easier than using a 914 tranny. The tail cone and inner shifter rods on the 914 tranny need to be replaced with the 901 parts anyways...so you should start with a 901 and call it a day.
Rich

[pcar916]

Or you could use a 901, not a 914 box, and your problems would be solved. Flipping the ring gear virtually requires you have the fixtures, which have been unavailable for decades (and were REALLY expensive when they were available).

The Cap'n

(IMG:style_emoticons/default/agree.gif)

Call EASY in CA. Last time I called he had quite a few of the 901 trannies ready to ship out.

Its alot easier than using a 914 tranny. The tail cone and inner shifter rods on the 914 tranny need to be replaced with the 901 parts anyways...so you should start with a 901 and call it a day.
Rich

Yeah... simple is good.

[jt914-6]

At a club race one time I saw a driver's mechanic working on his tranny. After he was done he went to test it. He had five reverse speeds and one forward. Driver said that he was used to working on 911's and "flipped" the R&P the wrong way......

[Dr Evil]

(IMG:style_emoticons/default/agree.gif) Simple is good

[ClayPerrine]

At a club race one time I saw a driver's mechanic working on his tranny. After he was done he went to test it. He had five reverse speeds and one forward. Driver said that he was used to working on 911's and "flipped" the R&P the wrong way......

Been there, done that..but in a 911. I did a 71 911 tranny one time, and had to take it all back apart because I installed the diff like a 914. (IMG:style_emoticons/default/headbang.gif)

That one ate my lunch, and it was worse because I know better and still did it. (IMG:style_emoticons/default/chair.gif)

[pcar916]

Oh yes... the early 915's have a 7:31 R&P if you like that ratio for your application.

[Dr Evil]

7:31 is stock 914/901 R&P.