Re: Broke 727 Tailshaft... Why?
[Re: Jimi_Vignogna]
#359411
06/28/09 08:35 PM
06/28/09 08:35 PM
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440Jim
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Quote:
it is the poly rear mount that caused it you cannot do that with solid engine mounts you need a solid rear trans mount.
I don't know his problem, but that isn't it, IMO. I have been running a front motor plate, with a fore-aft "limiter" (no movement) with a stock (new) rubber trans mount. 7-8 years, ladder bar rear suspension and minimal pinion angle (correct for ladder bars). And this car launches hard...
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Re: Broke 727 Tailshaft... Why?
[Re: Mopar_Mike]
#359416
06/29/09 07:57 AM
06/29/09 07:57 AM
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Posts: 13,496 Marion, South Carolina [><]
an8sec70cuda
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The poly trans mount is not the problem. I've been running a motorplate w/ a poly mount and haven't had a problem breaking tailshaft housings. In the past I broke two tailshaft housings, both times it was due to a twisted driveshaft. Had them checked at my local driveshaft shop and they were twisted. I twisted one stock driveshaft, broke the housing...replaced it with another stock shaft thinking it was a fluke. 3 passes later it twisted that shaft and broke another housing. I then had a custom 3" thickwall shaft built and never had another problem. This was with stock motor mounts (with a torque strap) and a poly trans mount. I later switched to the motorplate and installed a motor that makes 250 hp more and haven't had any problems. CHIP
CHIP '70 hemicuda, 575" Hemi, 727, Dana 60 '69 road runner, 440-6, 4 speed, Dana 60 '71 Demon 340, no drivetrain, on blocks behind the barn '73 Chrysler New Yorker, 440, 727, 8.75 '90 Chevy 454SS Silverado, 476" BBC, TH400, 14 bolt '06 GMC 2500HD LBZ Duramax
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Re: Broke 727 Tailshaft... Why?
[Re: an8sec70cuda]
#359417
06/29/09 08:41 AM
06/29/09 08:41 AM
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Posts: 4,288 Danville, NH
Mopar_Mike
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Thanks, this is looking more and more like it is a driveshaft problem. I do have frame ties and as mentioned the rear housing is stock with stock perches so it should be stock pinion angle.. right?
I know it is a custom shaft (was this way when I bought the car) and is xtra thick, 3"+
As mentioned above I did replace the differential yoke so length might be the issue there.
The trans is a 71 so it has only the rear yoke.
RS23L7 4-Speed
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Re: Broke 727 Tailshaft... Why?
[Re: Mopar_Mike]
#359418
06/29/09 10:05 AM
06/29/09 10:05 AM
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Posts: 75,282 A gulag near you.
JohnRR
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Quote:
Thanks, this is looking more and more like it is a driveshaft problem. I do have frame ties and as mentioned the rear housing is stock with stock perches so it should be stock pinion angle.. right?
I know it is a custom shaft (was this way when I bought the car) and is xtra thick, 3"+
As mentioned above I did replace the differential yoke so length might be the issue there.
The trans is a 71 so it has only the rear yoke.
Mike what rear springs are you using ?
I'd ditch the poly mount for now and run a rubber mount .
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Re: Broke 727 Tailshaft... Why?
[Re: JohnRR]
#359420
06/29/09 02:32 PM
06/29/09 02:32 PM
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Posts: 4,288 Danville, NH
Mopar_Mike
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John, I am using new (less than a year) cal-tracs 1" over ride height mono springs with the bars and rancho shocks.
RS23L7 4-Speed
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Re: Broke 727 Tailshaft... Why?
[Re: Mopar_Mike]
#359422
06/29/09 03:16 PM
06/29/09 03:16 PM
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JohnRR
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Quote:
John, I am using new (less than a year) cal-tracs 1" over ride height mono springs with the bars and rancho shocks.
Then you need to look at your pinion angle also as the spring can have an effect on it. The stock housing is ok with STOCK springs and their just good enough factory tolerance .
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Re: Broke 727 Tailshaft... Why?
[Re: JohnRR]
#359423
06/30/09 09:41 AM
06/30/09 09:41 AM
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Posts: 4,288 Danville, NH
Mopar_Mike
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Quote:
Quote:
John, I am using new (less than a year) cal-tracs 1" over ride height mono springs with the bars and rancho shocks.
Then you need to look at your pinion angle also as the spring can have an effect on it. The stock housing is ok with STOCK springs and their just good enough factory tolerance .
Whats the best way to measure pinion angle? I have been reading up on it, so I understand what it is and the need for a negative angle, but I am not understanding the best way to measure it.
If I need more of a negative angle what do you guys think of using wedges on the perches?
Last edited by Mopar_Mike; 06/30/09 09:42 AM.
RS23L7 4-Speed
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Re: Broke 727 Tailshaft... Why?
[Re: 440Jim]
#359425
06/30/09 09:53 AM
06/30/09 09:53 AM
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MR_P_BODY
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Quote:
Quote:
it is the poly rear mount that caused it you cannot do that with solid engine mounts you need a solid rear trans mount.
I don't know his problem, but that isn't it, IMO. I have been running a front motor plate, with a fore-aft "limiter" (no movement) with a stock (new) rubber trans mount. 7-8 years, ladder bar rear suspension and minimal pinion angle (correct for ladder bars). And this car launches hard...
I'm with Jim..... I would NEVER run a solid trans mount... if the chassis twists it will break the tail shaft For you pinion angle Caltracs calls for a 2*-4* angle (less than stock type springs due to less wind up)
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