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Kirkham Motorsports

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  • 1 Post By Cashburn

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  #1 (permalink)  
Old 06-07-2016, 11:34 AM
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Default Driveline Lash

The amount of lash in my drive train seems to have gotten worse and is irritating at times. When in first/second at low speeds it causes bucking motions that require slipping the clutch or coasting in order to eliminate it. Anyone have any comments on this issue?
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Old 06-07-2016, 12:20 PM
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Check all driveshaft bolts and most importantly that main diff bolt is very tight (like 3' breaker bar tight).
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Old 06-07-2016, 12:51 PM
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Quote:
Originally Posted by Cashburn View Post
Check all driveshaft bolts and most importantly that main diff bolt is very tight (like 3' breaker bar tight).
I'm with Jay... Either a loose FWD differential bolt or a broken FWD differential bolt.

Kevin.....
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Old 06-07-2016, 03:52 PM
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Originally Posted by Kobura View Post
The amount of lash in my drive train seems to have gotten worse and is irritating at times. When in first/second at low speeds it causes bucking motions that require slipping the clutch or coasting in order to eliminate it. Anyone have any comments on this issue?
Had this issue I had a broken drive shaft bolt and for some reason it would actually grab and the vehicle would move but bucked in 1st. Though after bucking started I only drove it maybe 2 miles.
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Old 06-07-2016, 04:05 PM
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This thread has some good info

What causes an engine to 'buck' at low speeds?
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Old 06-07-2016, 05:27 PM
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Originally Posted by spdbrake View Post
This thread has some good info

What causes an engine to 'buck' at low speeds?
That is a good point, is this an engine tuning/camshaft trait or driveline issue?

Gary
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Old 06-07-2016, 05:31 PM
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Sounds like "trailer hitching". A healthy cam is usually part of the reason - but light springs on the centrifugal advance can aggravate it with advance swinging in and out with surges in the engine rpm. If it's gotten worse a thorough check of timing and carb settings might be in order.
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Old 06-07-2016, 06:43 PM
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Don't worry just drive it...
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Old 06-08-2016, 11:22 AM
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I checked for loose nuts and bolts on the driveshaft and for indications of anything loose. Everything appears to be tight. I grabbed both rear tires and rotated one of them that moved about an inch at the tread. The driveshaft rotated in synch with the tire. My conclusion is that the lash is in the transmission. Any comments?
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Old 06-08-2016, 01:28 PM
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Originally Posted by Kobura View Post
I checked for loose nuts and bolts on the driveshaft and for indications of anything loose. Everything appears to be tight. I grabbed both rear tires and rotated one of them that moved about an inch at the tread. The driveshaft rotated in synch with the tire. My conclusion is that the lash is in the transmission. Any comments?

As Jay and I both said.. you need to check to see if bolt #17 has sheared. This bolt connects the front of the differential to the subframe.

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Old 06-08-2016, 03:18 PM
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Default bucking problem

My small block does this, too. I like my idle speed as low as possible. But, if I increase it a couple hundred RPM's, the bucking is no longer a problem.
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Old 06-08-2016, 05:59 PM
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I verified that nothing is amiss with the differential attachment to the car frame for which I am very thankful as a loose differential could be disastrous. The schematic diagram of the e36 rear end was helpful although my hardware appears to be slightly different. e.g., hex socket bolts instead of hex head bolts and a different attachment scheme. So, unless I hear otherwise, I will follow the advise of our favorite BDR skeptic 'cbreez' and not worry and just drive it.
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