I’m just about to start taking out a Chevy 350 with a 4l60e out of my 1994 GMC 1500 and I’m stuffing a 455 with a BOP TH400 in it. Has anyone done an Oldsmobile V8 swap on one of these GMT400 chassis?

Thanks

 

Sounds like a cool swap. Hopefully someone can give you some good advice. Good luck.👍

 

Yes, I have, ran the factory TBI and 4L60E on an Olds 350 with a 307 CCC distributor. Are you running a carb? You can just hook up off the TBI and just pull through with the mechanical pump. Is it 2WD or 4WD? You need the 403 Trans Am complete motor mounts. Even then I had to add spacers. Manifolds or shorty headers, along with custom exhaust will be needed. You will need a custom driveshaft with the TH400. What rear gears are in your truck? A 4L80E is a nice swap and on my list if I find another to Olds power. Good luck, all that torque will make it fun.

 

Truck is already converted to run a carburetor. Nothing is wrong with the 350, I just got the 455 for free and the trans for free from my uncle who ls swapped an olds 98 for one of his customers. I’m a few bolts away from the 350 coming out. Truck has 3.55 rear gears in it and it is 2wd. Bad news is that I’m a broke college student. Good news is that I am studying mechanical engineering and am a good welder/fabricator/machinist so I’m probably gonna end up making my own mounts for the engine and trans. I did some measurements and the current exhaust manifolds will fit in the engine bay. Hopefully the fabricobbling isn’t as bad as I’m expecting it to be.

Front clip is ready to be lifted off. Featuring my buddy being a goofball.

 

Yeah it won't be hard, especially on a 2WD. With the 455 and 3.55 gears, it will spin the tires hard but run 1000 rpm higher on the highway with the TH400 vs the factory 4L60E. Does the the TH400 have a provision for a speedometer cable? The 4L60E can be used with an adapter plate and is obviously functioning with the current carb, if mileage is important.

 

I’ll gather I’m late in this conversation but regardless of your skill set, if you’re a broke-*** youngster trying to finish a degree you’d be best to leave it alone. Focus on your schooling and save the 455 for a future project. Aside from the obvious fuel consumption differences, the factory Tbi 350 would reliably and safely get you where you’re going. Nobody is going to get overly excited about an OBS GMC with an Olds BB..especially when the later model LS guys are walking all over you. You should concentrate all of your capacities into finishing your education right now. You’ll have a lifetime to get creative once you’ve achieved that. Stay focused. Reap the rewards later.

 

Excellent advice you have given this your man Heath. I am afraid we are a little late though.

 

Probably not too late to reassemble. When I was in school (and broke), my Buick collected a whole lot of dust. Right after graduating I received a nice bonus from my work and did a Tremec TKO conversion. Circa 1999!

 

As long as it’s not his only vehicle, and has reliable transportation, I say 455 swap it!! Lord knows there are plenty of LS swaps in the world, life is too short to blend in.

As for the speedo, if you can find the parts the last year or 2 of the TH400 production they had tone wheels and speed sensors to work with stepper motor style speedometers. I know FTI transmission offers the tone wheel that goes on the output shaft, the speed sensor is kinda hard to find. I used this setup on my brother in laws 85 cutlass when he installed Autometer gauges, and I have used these parts on a few F body 400 conversions.