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914World.com _ 914World Garage _ Comments on bondo's gearbox thread

Posted by: lapuwali Oct 5 2004, 05:47 PM

In addition to his excellent series of photos and running commentary (classic thread in the making...), some things I picked up disassembling other gearboxes (haven't done a 914, yet) for anyone else contemplating doing this themselves:

1. Engines tend to have lots of parts that look very different, or are interchangable if they are the same. Gearboxes tend to have lots of parts that look the same, but are different. Rebuilding a gearbox is NOT the same as rebuilding an engine. Organization is much more important. Put the parts in labelled bags or boxes when disassembling, or lay them out flat on a clean table, in order. Many people end up reassembling weeks or months after disassembly, so label everything very carefully.

2. Gear teeth are SHARP! Do not grab a gear with your bare hand and attempt to twist or pull it, or you have a very good chance of cutting yourself. Wear heavy gloves or use a rag.

3. Gearboxes nearly always have shims who's exact place and even spacing are important if you want everything to mesh together properly later. Failing to do this will, at best, produce a noisy-running 'box. At worst, parts will break early. Bondo's thread notes which washers of which thicknesses go where, but the order and thickness may be different for your gearbox, so measure everything yourself.

4. Cleanliness in a gearbox is even more important than in an engine. Engines have rapidly circulating oil systems with filters. Gearboxes do not. The bearings in the 901 'box are expensive and vulnerable to bits of grit or metal shavings contaminating the gear oil. A parts washing tub with lots of solvent is a great thing to have when rebuilding a gearbox.

5. Gear oil smells awful, and the scent lingers for a good, long time. To promote marital bliss, work in a well-ventilated space with the exhaust air pointing away from the rest of the house. Have a gearbox rebuilding outfit that you never wear inside.

Posted by: Bleyseng Oct 5 2004, 06:36 PM

Good points

Posted by: bondo Oct 5 2004, 06:44 PM

Thanks for the kind words. Good points too. (I've already cut myself twice, but out of 7 transmissions that ain't bad) As far as each transmission having different shims, that is a dillemma I have been contemplating. I'm trying to make one good transmission out of several mediocre ones, including one gear from a 912. All these different parts coming together is going to make things interesting to say the least.