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oil pan 4 · 02-05-2016, 01:14 AM

The 3800 engine has its own unique bolt pattern.
I have no idea what bolt pattern the 2.5L used. I believe 60 degree V6 and 4cyl used the same transmission bolt pattern through the 70s, 80s and part of the 90s.
The 4.3L, all generations of SBC to include LT and LS series, BBC (all generations), 6.2+6.5L diesel, duramax, have interchangeable bolt pattern.
Not only do most of those share the same transmission but if they don't have the same engine mount then there are off the shelf adaptors you can buy for cheap.
You can put a TH700 transmission or NV3500 behind the old chevy diesels.
IF you want a 2.5L then I am pretty sure you are stuck with the T-5 made for 4 cylinders and V-6 motors.

GM tried sticking under sized engines in over sized vehicles in the late 80s and early 90s, these vehicles really didn't get noticeably better fuel economy than their larger engine counter parts.
These little engines just got ran a lot harder than the V8 motors and went to the junk yards sooner.

02-05-2016, 01:14 AM	#2 (permalink)
oil pan 4 Corporate imperialist Join Date: Jul 2011 Location: NewMexico (USA) Posts: 11,181 Sub - '84 Chevy Diesel Suburban C10 SUV 90 day: 19.5 mpg (US) camaro - '85 Chevy Camaro Z28 Riot - '03 Kia Rio POS Team Hyundai 90 day: 30.21 mpg (US) Bug - '01 VW Beetle GLSturbo 90 day: 26.43 mpg (US) Sub2500 - '86 GMC Suburban C2500 90 day: 11.95 mpg (US) Snow flake - '11 Nissan Leaf SL SUV 90 day: 141.63 mpg (US) Thanks: 270 Thanked 3,524 Times in 2,798 Posts	The 3800 engine has its own unique bolt pattern. I have no idea what bolt pattern the 2.5L used. I believe 60 degree V6 and 4cyl used the same transmission bolt pattern through the 70s, 80s and part of the 90s. The 4.3L, all generations of SBC to include LT and LS series, BBC (all generations), 6.2+6.5L diesel, duramax, have interchangeable bolt pattern. Not only do most of those share the same transmission but if they don't have the same engine mount then there are off the shelf adaptors you can buy for cheap. You can put a TH700 transmission or NV3500 behind the old chevy diesels. IF you want a 2.5L then I am pretty sure you are stuck with the T-5 made for 4 cylinders and V-6 motors. GM tried sticking under sized engines in over sized vehicles in the late 80s and early 90s, these vehicles really didn't get noticeably better fuel economy than their larger engine counter parts. These little engines just got ran a lot harder than the V8 motors and went to the junk yards sooner. __________________ 1984 chevy suburban, custom made 6.5L diesel turbocharged with a Garrett T76 and Holset HE351VE, 22:1 compression 13psi of intercooled boost. 1989 firebird mostly stock. Aside from the 6-speed manual trans, corvette gen 5 front brakes, 1LE drive shaft, 4th Gen disc brake fbody rear end. 2011 leaf SL, white, portable 240v CHAdeMO, trailer hitch, new batt as of 2014. Last edited by oil pan 4; 02-05-2016 at 01:29 AM..