Shifter question, Going from 1st to 2nd... |
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Shifter question, Going from 1st to 2nd... |
jim_hoyland |
May 16 2013, 03:50 PM
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#1
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Get that VIN ? Group: Members Posts: 9,418 Joined: 1-May 03 From: Sunset Beach, CA Member No.: 643 Region Association: Southern California |
I was wondering whether all 914's inherently are unable to shift from 1st to second without quickly--a slight hesitation has been my experience.
The bushing had been replaced, the shifter is a J West rennshift,tranny was rebuilt by Dr Evil, and it shifts fine from 2 to 3, and 4 to 5. Three to four takes a little work, but a lot less than 1 to 2 Any experience or suggestions here ? (IMG:style_emoticons/default/smile.gif) |
Eric_Shea |
May 17 2013, 09:57 AM
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#2
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PMB Performance Group: Admin Posts: 19,289 Joined: 3-September 03 From: Salt Lake City, UT Member No.: 1,110 Region Association: Rocky Mountains |
My understanding is that hesitation is the end result of the original "Porsche-Type" syncromesh transmission design.
Could lube be the culprit? I know in my tranny, a modern lube prevented an easy shift into fist at a stop light as the "slippery'er'er'er" lube didn't allow the syncros to play with one another as they should. Put some big, fat dyno lube in there if you haven't already and see if it makes a difference. From the Wiki: Synchromesh Synchronizer rings If the teeth, the so-called dog teeth, make contact with the gear, but the two parts are spinning at different speeds, the teeth will fail to engage and a loud grinding sound will be heard as they clatter together. For this reason, a modern dog clutch in an automobile has a synchronizer mechanism or synchromesh, which consists of a cone clutch and blocking ring. Before the teeth can engage, the cone clutch engages first, which brings the selector and gear to the same speed using friction. Moreover, until synchronization occurs, the teeth are prevented from making contact, because further motion of the selector is prevented by a blocker (or baulk) ring. When synchronization occurs, friction on the blocker ring is relieved and it twists slightly, bringing into alignment certain grooves and notches that allow further passage of the selector which brings the teeth together. Of course, the exact design of the synchronizer varies from manufacturer to manufacturer. The synchronizer[3] has to overcome the momentum of the entire input shaft and clutch disk when it is changing shaft rpm to match the new gear ratio. It can be abused by exposure to the momentum and power of the engine itself, which is what happens when attempts are made to select a gear without fully disengaging the clutch. This causes extra wear on the rings and sleeves, reducing their service life. When an experimenting driver tries to "match the revs" on a synchronized transmission and force it into gear without using the clutch, the synchronizer will make up for any discrepancy in RPM. The success in engaging the gear without clutching can deceive the driver into thinking that the RPM of the layshaft and transmission were actually exactly matched. Nevertheless, approximate rev. matching with clutching can decrease the general change between layshaft and transmission and decrease synchro wear. |
worn |
May 17 2013, 10:57 AM
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#3
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can't remember Group: Members Posts: 3,290 Joined: 3-June 11 From: Madison, WI Member No.: 13,152 Region Association: Upper MidWest |
My understanding is that hesitation is the end result of the original "Porsche-Type" syncromesh transmission design. Could lube be the culprit? I know in my tranny, a modern lube prevented an easy shift into fist at a stop light as the "slippery'er'er'er" lube didn't allow the syncros to play with one another as they should. Put some big, fat dyno lube in there if you haven't already and see if it makes a difference. I was surprised how difficult it was to get the synchros to shift when new. So how fat should the dinosaur be? i.e. any oil recommendations? as per my other posts I am planning to use roofing tar as motor oil to get the pressure up, but that may not be quite the thing for the transmission. |
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