Just found a Olds 455 and a TH400 for my 86' Cutlass

[sadisticsavage]

Found a Olds 455 and a TH400 transmission for my 1986 Cutlass. After reading some posts I found that the 455 is a easy swap. Will work with the original 307 mounts and hardware. But the transmission is where I'll need help. Some said it will bolt right into the original location of the 200R4 and some said I'd need a new crossmember? And that the 400 is longer than the 200 so I'd need a new driveline or get it chopped and balanced. Has anyone done this swap before and if so what were you problems that you ran into? I did the best research I could but just found potential problems I'd have and no concuslusions. I appreciate any help as this is my 1st Olds. Thanks!

 

[littlerascle59]

Found a Olds 455 and a TH400 transmission for my 1986 Cutlass. After reading some posts I found that the 455 is a easy swap. Will work with the original 307 mounts and hardware. But the transmission is where I'll need help. Some said it will bolt right into the original location of the 200R4 and some said I'd need a new crossmember? And that the 400 is longer than the 200 so I'd need a new driveline or get it chopped and balanced. Has anyone done this swap before and if so what were you problems that you ran into? I did the best research I could but just found potential problems I'd have and no concuslusions. I appreciate any help as this is my 1st Olds. Thanks!

If you're going to use the TH-400 transmission, you're going to have to convert it to short tail if it's a long tail transmission.
Once you do that you'll also need to have your drive shaft cut about .075 - 1" if I remember right. The cross member will need to be custom made or you'll have to use another crossmember with mounting holes drilled in it. You'll also need another radiator or use the radiator from the donor car that the engine and transmission came out of but you'll have to probably have to notch the core support like I did with mine in order for the bigger radiator to fit & you'll have to notch a little where the transmission lines bolts to radiator to so that the bottom line can go in. I have a 1986 Cutlass too and my engine and transmission came out of a 1976 Olds 98 Regency. If I were you, I'd use the 200-4R transmission over the TH-400 tho, that's just me tho.

 

[Blake442]

The TH-400 was available in 3 different tailshaft lengths. This is assuming the transmission you plan on buying is a short tail...

200-R4 and TH-400 use the same crossmember and mount.
You will need a new slip yoke and the driveshaft will have to be shortened 1/2 to 3/4 of an inch or so.
Measure your car after it's assembled to confirm what you need.
I had my driveshaft cut and balanced for about $90.

I got a direct bolt-in aluminum radiator, new HD fan clutch and 7 blade fan to keep it cool. The stock HD radiator couldn't keep up.
I modified the ends of my original cooler lines to work with the different arrangement of the TH-400.

 

[jociha]

The 455 is a big block so it is a bit wider and taller [about an inch each way]. If your car came with A/C then you will have trouble with the passenger valve cover, it will hit the A/C. You can notch the A/C others on here have done it, and a little re-fiberglassing and your good. If you plan on dual exhaust get a G-force crossmember, it is a double hump as your original is not, and as said in last post if you have a short tail trans then the cross member will bolt in to existing holes, then as said you will need to fix your driveshaft.

 

[littlerascle59]

My crossmember must've been for something else instead of a 200-4R because mine wouldn't work without me having to put extra holes in it.
Good to know tho, now I guess I gotta find me a stock 200-4R crossmember.

 

[Blake442]

Clearance between the valve cover and a/c box is close but should be fine unless your body mounts are extremely worn.

 

[STL84Calais]

Yes, it is close, to get mine to fit, we had to ever-so-slightly dent the passenger side valve cover to make it not rub. My cross member is a 200-4r cross member, cut for dual exhaust and it works great! I have a short tail TH400. See my build thread for details.

 

[sadisticsavage]

The Transmission is ready to go, had the tailshaft shortened. Just need to shorten the driveline. Thanks for the heads up on the A/C! Will definately keep that in mind. Hopefully mine clears but I'll be ready to knotch it. And does anyone have a pair of headers for the 455 in a G-body? If not where can I find some online or anyone on here?

 

[littlerascle59]

The Transmission is ready to go, had the tailshaft shortened. Just need to shorten the driveline. Thanks for the heads up on the A/C! Will definately keep that in mind. Hopefully mine clears but I'll be ready to knotch it. And does anyone have a pair of headers for the 455 in a G-body? If not where can I find some online or anyone on here?

Since I'm limited on resources around here because I'm in a more rural area, most likely I'm gonna put W/Z manifolds on mine. Found some within my poor man's budget online.

 

[STL84Calais]

The Transmission is ready to go, had the tailshaft shortened. Just need to shorten the driveline. Thanks for the heads up on the A/C! Will definately keep that in mind. Hopefully mine clears but I'll be ready to knotch it. And does anyone have a pair of headers for the 455 in a G-body? If not where can I find some online or anyone on here?

Unless you're ready to spend $800 on headers, your best bet will be W-Z manifolds. New castings can be had online for about $250. I'm running W-Z manifolds on mine, they flow about the same as a shorty header. They have individual runners for each exhaust port.