From: "Brandon" To: "928" <928@rennlist.org> Sent: Monday, October 08, 2001 10:36 AM Subject: [928] Where did 4th go? > I was driving my 84's 5 speed last night crusing along in fourth gear and > boom the car goes out of gear.... I place the stick in 4th and no 4th? It > sounds like the linkage to me but all my other gears are fine. > Does anyone have any other Ideas what it could be...God I hope its not the > tranny... > > Thanks, > BB > 84 Black 5 speed. From: Dave Cooley [mtcarrera@sofast.net] Sent: Monday, October 08, 2001 6:16 PM To: 928 Subject: [928] Re: Where did 4th go? All five gears on a 928 transmission are engaged with a combination of dog teeth (pressed onto the gearset itself) and operating sleeves (slid onto the dog teeth with the shift forks). One of the costs of missed/clashed shifts is dulling or breaking the dog teeth. Under the worst of conditions the dog teeth are broken completely and that gear won't engage at all. When the dog teeth and operating sleeves get worn, then can disengage while under tremendous force (as in acceleration) and do themselves some severe damage, and when this begins to happen it's time for a rebuild. Externally, the gears are selected in pairs (1/R, 2/3, 4/5). You select the pair by how far right or left you position the shifter, and the specific gear by moving it forward or back. If you can select reverse and 2nd gear, then the linkage can move far enough forward (actually backwards at the transaxle), and if you can select 5th, you can move the linkage far enough right. Being unable to select 4th tells me that the dog teeth in 4th are toast. Sadly, I think your transaxle is going to have to be rebuilt. Dave From: Jim Bailey [mailto:jim@928intl.com] Sent: Tuesday, October 15, 2002 12:25 PM To: 928 Subject: [928] Re: Kelly Moss Racer / 911 vs 928 Dyno Numbers Jay..."Is the 5th gear setup in the 928 unique in the Porsche transmission world?" Yes it is quite different in many respects , including the use of 5th gear as the input shaft for all gears which means in gears 1-4 power must be transferred from the 5th gear by way of lay shaft drive gears to the parallel lay shaft then must pass through another set of gears to get back to the pinion shaft to drive the ring gear and turn the axles . Only in 5th does power go directly to the pinion shaft with no losses from passing through any gears on the way to the ring and pinion gears . The usual Porsche transmission power is always going through one set of gears in all gears . The 928 in gears 1-4 it passes through two sets but in 5th it is DIRECT . This means the 928 transmission is less efficient (has more drag , friction and generates more heat)in gears 1-4 but more efficient in 5th gear , just what you would expect given the designed use for the 928 . Better efficiency in the high speed touring gear 5 th with some inefficiency in the lower gears . Simply stated any time power is forced to change directions you must pay a price as energy is lost converted to heat . Jim Bailey 928 International Jim@928intl.com www.928intl.com (714)632-9288