Transmission problem

Road-race engines and ancillaries - general discussion
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Henry
Posts: 4
Joined: January 8th, 2008, 4:06 am

Transmission problem

Post by Henry » July 11th, 2009, 3:59 pm

The 4th gear synchro on my 2L FI was changed about two weeks ago and the 4th is popping out again, any suggestions?

Jon_Logan
Posts: 9
Joined: June 22nd, 2006, 11:41 am
Location: Hilliard, Ohio USA
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Re: Transmission problem

Post by Jon_Logan » July 12th, 2009, 11:16 pm

Henry,
Popping out of gear is NOT a synchro problem but instead either a slider gear or a shift fork. More likely the shift fork. When drivers rest their hand on the shift lever when driving, it forces the fingers of the shift fork inside the groove of the slider gear, wearing both the slider and the shift fork. When the fork can no longer fully engage the gear with the slider, the transmission will pop out of gear, often under deceleration.

Synchro only meets up the gear and the slider without grinding.
Jon W. Logan
Midwest-124
http://www.midwest124.com
parts@midwest124.com
1979 Fiat Spider 2000, 10:1, Twin IDFs

Henry
Posts: 4
Joined: January 8th, 2008, 4:06 am

Re: Transmission problem

Post by Henry » July 14th, 2009, 4:27 am

What about worn main shaft?

Jon_Logan
Posts: 9
Joined: June 22nd, 2006, 11:41 am
Location: Hilliard, Ohio USA
Contact:

Re: Transmission problem

Post by Jon_Logan » July 14th, 2009, 11:24 am

No, the main shafts are pretty robust. Unless the transmission was run chronically low on lubricant, the main shaft would be fine. Also possible that the front thrust washer between the front seal carrier and the input shaft may have been installed reversed allowing the input shaft to move ever so slightly forward under deceleration causing 4th gear to pop out.
Jon W. Logan
Midwest-124
http://www.midwest124.com
parts@midwest124.com
1979 Fiat Spider 2000, 10:1, Twin IDFs

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