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09-21-2018, 06:58 PM | #1 |
Registered User
Join Date: Oct 2017
Location: Poplar Bluff Mo
Posts: 21
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91 GMC Crossmember
So I put a 454 with a TH350 trans in a 91 GMC. The headers and the crossmember are almost in line with each other and not looking like a 3 inch exhaust will work. I found a universal crossmember from Summit pretty reasonably priced but it says it's a 3 or 6 inch drop or flat. I have no idea how much of a drop if any is needed. Or how wide it needs to be. Any advise would be most greatly appreciated.
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09-21-2018, 11:03 PM | #2 |
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Join Date: Oct 2011
Location: Tucson, AZ
Posts: 639
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Re: 91 GMC Crossmember
Been a while but here I go.
If I remember right your current crossmember is flat. You want to think of the drop as a lift. Use that drop to mount the crossmember to the upper part of the frame as apposed to the lower part. This will leave your transmission in its current location while moving the crossmember up for clearance. Other options also available.
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09-21-2018, 11:37 PM | #3 |
60-66 Nut
Join Date: Mar 2007
Location: Coeur d'Alene, Idaho
Posts: 23,246
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Re: 91 GMC Crossmember
Is your '91 GMC a R/V series or is it the GMT400 platform?
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09-22-2018, 02:20 AM | #4 |
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Join Date: Oct 2017
Location: Poplar Bluff Mo
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Re: 91 GMC Crossmember
I'm sorry, I should have said it's 1/2 ton 2wd short bed regular cab. Don't know why I forgot that.
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09-22-2018, 11:46 PM | #5 |
60-66 Nut
Join Date: Mar 2007
Location: Coeur d'Alene, Idaho
Posts: 23,246
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Re: 91 GMC Crossmember
So the universal trans crossmember you found is wide enough for the GMT400 frame? If so, then that would be the way to go with mounting it up at the top of the frame. You'll just have to measure how much drop you need. I would imagine a 6" drop.
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Power Steering Box Adapter Plates For Sale HERE Power Brake Booster Adapter Brackets For Sale '63-'66 HERE and '67-'72 HERE and '60-'62 HERE and "60-'62 with clutch HERE Rear Disc Brake Brackets For Sale. Impala SS calipers HERE Camaro Calipers HERE D52 Calipers HERE 6 Lug HERE Hydroboost Mounting Plates HERE |
09-23-2018, 09:00 PM | #6 |
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Join Date: Oct 2017
Location: Poplar Bluff Mo
Posts: 21
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Re: 91 GMC Crossmember
Should I measure it from the top of the frame to the top of the factory crossmember to get the drop I need for sure? I'm gonna have to check my measurements again on the inside of the frame. The universal mount is 36 inches wide and now I'm not sure if that's for a S-10 type truck of full size. Is the GMT400 the designation for a full size truck? I've never seen that before.
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