6.0 LQ9 4L65E swap 71 GMC 2500 - The 1947 - Present Chevrolet & GMC Truck Message Board Network

RR440MAN · 08-25-2019, 04:25 AM

My son and I are restoring a 71 GMC 2500 and swapping a 6.0 LQ9 with a 4L65E. Today we stabbed in the engine and transmission into the chassis for a test fit prior to removing for media blasting. We fitted the engine plates and mounts onto the stock perches. It looks like we are going to have to move the engine further rearward on the plates as we are having difficulty clearing the perches with the passenger side header. There is an approximate 1/16” clearance of the passenger side perch. The engine angle and transmission appear to be approximately 2.5-3 degrees so I think we are good. The long tube headers will necessitate either fabricating a new transmission crossmember or purchase one with provisions for a 3” exhaust clearance. What trans crossmembers are you guys/girls running to facilitate clearance for a 3” exhaust? Attached are photos of the build.

**mongocanfly** · 08-25-2019, 07:16 AM

I built my own crossmember but its similar to the store bought ones..except mine is double tubes...why 3in exhaust?

RR440MAN · 08-25-2019, 12:04 PM

That’s a nice fab job! I wish I had a tubing bender. My headers have 2 3/4” collectors but I say 3” because I would like some wiggle room and the collectors are pretty close to the trans crossmember. We initially have plans to have a drivers side inside frame fuel tank. After exiting past/ through the crossmember the drivers side exhaust will bend 90 degrees and route side by side into a two into one muffler.

**Captainfab** · 08-25-2019, 11:44 PM

I wouldn't move the engine back too far without the cab in place to check firewall clearance. Are those Speed Engineering headers? You could clearance the engine mount bracket to gain a little room.

**MDPotter** · 08-26-2019, 10:26 AM

I just fabbed up a crossmember, it's pretty easy. Just make sure you have the pinion angle where you want it and that the driveshaft has the right clearance through the other crossmember (allowing for suspension travel as well).

RR440MAN · 06-03-2022, 04:32 PM

We actually ended up going with an aftermarket Trans mount and I had to fab up a mount spacer to get the pin in angle correct tor the drivelines. Moved the engine mount farther forward as well. Seems to be coming along. It’s been slow progress since it’s a father /son project but we’re ramping up. Finishing up Brake lines and oil engine/trans cooler hoses and mounts for the oil coolers.

08-25-2019, 04:25 AM	#1
RR440MAN Registered User Join Date: Oct 2017 Location: Bakersfield California Posts: 17	6.0 LQ9 4L65E swap 71 GMC 2500 My son and I are restoring a 71 GMC 2500 and swapping a 6.0 LQ9 with a 4L65E. Today we stabbed in the engine and transmission into the chassis for a test fit prior to removing for media blasting. We fitted the engine plates and mounts onto the stock perches. It looks like we are going to have to move the engine further rearward on the plates as we are having difficulty clearing the perches with the passenger side header. There is an approximate 1/16” clearance of the passenger side perch. The engine angle and transmission appear to be approximately 2.5-3 degrees so I think we are good. The long tube headers will necessitate either fabricating a new transmission crossmember or purchase one with provisions for a 3” exhaust clearance. What trans crossmembers are you guys/girls running to facilitate clearance for a 3” exhaust? Attached are photos of the build. Attached Images

08-25-2019, 07:16 AM	#2
mongocanfly Post Whore Join Date: May 2015 Location: Alabama Posts: 14,670	Re: 6.0 LQ9 4L65E swap 71 GMC 2500 I built my own crossmember but its similar to the store bought ones..except mine is double tubes...why 3in exhaust? Attached Images __________________ Mongo...aka Greg RIP Dad RIP Jesse 1981 C30 LQ9 NV4500..http://67-72chevytrucks.com/vboard/s...d.php?t=753598 Mongos AD- LS3 TR6060...http://67-72chevytrucks.com/vboard/s...34#post8522334 Columbus..the 1957 IH 4x4...http://67-72chevytrucks.com/vboard/s...63#post8082563 2023 Chevy Z71..daily driver

08-25-2019, 12:04 PM	#3
RR440MAN Registered User Join Date: Oct 2017 Location: Bakersfield California Posts: 17	Re: 6.0 LQ9 4L65E swap 71 GMC 2500 That’s a nice fab job! I wish I had a tubing bender. My headers have 2 3/4” collectors but I say 3” because I would like some wiggle room and the collectors are pretty close to the trans crossmember. We initially have plans to have a drivers side inside frame fuel tank. After exiting past/ through the crossmember the drivers side exhaust will bend 90 degrees and route side by side into a two into one muffler. Attached Images Last edited by RR440MAN; 08-25-2019 at 12:10 PM. Reason: Pictures

08-25-2019, 11:44 PM	#4
Captainfab 60-66 Nut Join Date: Mar 2007 Location: Coeur d'Alene, Idaho Posts: 23,252	Re: 6.0 LQ9 4L65E swap 71 GMC 2500 I wouldn't move the engine back too far without the cab in place to check firewall clearance. Are those Speed Engineering headers? You could clearance the engine mount bracket to gain a little room. __________________ 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

08-26-2019, 10:26 AM	#5
MDPotter Senior Member Join Date: Aug 2018 Location: Western Colorado Posts: 1,165	Re: 6.0 LQ9 4L65E swap 71 GMC 2500 I just fabbed up a crossmember, it's pretty easy. Just make sure you have the pinion angle where you want it and that the driveshaft has the right clearance through the other crossmember (allowing for suspension travel as well). __________________ 1964 Chevy C10 - Gen IV 5.3 Restomod http://67-72chevytrucks.com/vboard/s...d.php?t=768632 1968 GMC C15 - Gen III 6.0 Restomod http://67-72chevytrucks.com/vboard/s...d.php?t=772047 1969 Chevy C10 - Restoration http://67-72chevytrucks.com/vboard/s...d.php?t=809184 1978 Chevy Scottsdale K20 1993 Chevy C1500 - 5.3/T56 swapped 2008 Silverado Duramax

06-03-2022, 04:32 PM	#6
RR440MAN Registered User Join Date: Oct 2017 Location: Bakersfield California Posts: 17	Re: 6.0 LQ9 4L65E swap 71 GMC 2500 We actually ended up going with an aftermarket Trans mount and I had to fab up a mount spacer to get the pin in angle correct tor the drivelines. Moved the engine mount farther forward as well. Seems to be coming along. It’s been slow progress since it’s a father /son project but we’re ramping up. Finishing up Brake lines and oil engine/trans cooler hoses and mounts for the oil coolers. Attached Images



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