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08-11-2014, 12:22 AM
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#1 |
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Junior Member
Join Date: Aug 2009
Location: Calgary Alberta
Posts: 21
Likes: 1
Liked 7 Times in 2 Posts
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Re: Coan XLT Turbo 350 Issues
After the first time this trans smoked the clutches-1 pass down the track (Coan had just freshened this trans) , Coan has since updated the valve body, supplied a new pump and an oil pan with baffles in it for a super stock application( it was not free) . According to them, this is everything I needed. they also supplied every spec on clearances etc. What happened?? We hooked up a pressure gauge and are at a constant 200 psi at all forward gears, reverse, and with the transbrake engaged at 2000 + rpm.
 I am having trouble finding that this could happen twice in 2 freshens after one hit on the track (one freshen by Coan and one by a rep trans builder) . Coan's site talks about wheel standing cars and fluid cavitation. I eliminated this-tied down that front end. Minimal wheel stand action-same problem. very frustrating!
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6521 GT/MA 85 Cutlass Last edited by Charlene Gullett; 08-11-2014 at 12:26 AM. |
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08-11-2014, 02:58 AM
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#2 |
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Junior Member
Join Date: Feb 2013
Location: Pasco, Wa.
Posts: 15
Likes: 0
Liked 3 Times in 2 Posts
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Re: Coan XLT Turbo 350 Issues
There are two other pressure test ports on the TH350 case. One next to the accumulator is the intermediate clutch and the one under the cooler fittings is the direct clutch. Some may have one near the line pressure tap for reverse, some may have the boss cast in but not drilled and tapped. I would test those in every gear to make sure they have the correct pressure when they are supposed to and none when they're not, like direct clutch pressure in clean neutral. I wonder if the manual valve is not positioned correctly and not fully exhausting 3rd gear. Are you using the shifter that's required for the clean neutral trans?
Last edited by James Packer; 08-11-2014 at 03:10 AM. |
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08-11-2014, 02:43 PM
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#3 |
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Junior Member
Join Date: Aug 2009
Location: Calgary Alberta
Posts: 21
Likes: 1
Liked 7 Times in 2 Posts
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Re: Coan XLT Turbo 350 Issues
Mystery solved! Behind the governor cap Coan has installed a Holley jet that controls pressure and bleed off for the direct clutches. I guess this is sensitive to your application and it can burn the clutch pack in a heartbeat if you do not have the correct jet.
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6521 GT/MA 85 Cutlass |
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08-11-2014, 02:51 PM
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#4 |
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Junior Member
Join Date: Feb 2013
Location: Pasco, Wa.
Posts: 15
Likes: 0
Liked 3 Times in 2 Posts
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Re: Coan XLT Turbo 350 Issues
Cool, glad you found it.
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08-11-2014, 02:59 PM
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#5 |
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Junior Member
Join Date: Feb 2013
Location: Pasco, Wa.
Posts: 15
Likes: 0
Liked 3 Times in 2 Posts
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Re: Coan XLT Turbo 350 Issues
When the fluid can't bleed out of drum centrifugal force will try to apply the clutches.
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08-11-2014, 05:02 PM
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#6 |
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Senior Member
Join Date: Feb 2002
Location: Southeast Michigan
Posts: 909
Likes: 70
Liked 239 Times in 114 Posts
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Re: Coan XLT Turbo 350 Issues
What jet was in there ? What jet are you going to install ? Was this a suggestion from Coan ? Thanks for an update !
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08-11-2014, 07:32 PM
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#7 |
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Junior Member
Join Date: Aug 2009
Location: Calgary Alberta
Posts: 21
Likes: 1
Liked 7 Times in 2 Posts
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Re: Coan XLT Turbo 350 Issues
Popped the cap off and yup there is a jet there. Didn't look at the size. Coan made no suggestion. They want to see the Trans back. So I am hoping they will be able to help me out, since this is the second failure.
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