1978 transmission hump

[DBear]

Does anyone know if the the Trans hump in a 1978 2wd crew cab bolt in or is it part of the floor as one piece? I know that the k30 manual trans version of this cab has a bolted Trans hump but I need to know if a 2wd auto cab's Trans hump is bolted as well? Thanks in advance

[Titomars]

The low hump is part of the floor, not removable. the high hump is bolted in. Automatics and 3 speeds use the low hump, 4 speeds use the high hump

[donut]

High hump also in the 4wd. http://forum.73-87chevytrucks.com/sm...88158#msg88158

[El Dorado Jim]

Originally Posted by DBear

Does anyone know if the the Trans hump in a 1978 2wd crew cab bolt in or is it part of the floor as one piece? I know that the k30 manual trans version of this cab has a bolted Trans hump but I need to know if a 2wd auto cab's Trans hump is bolted as well? Thanks in advance

If it is a low hump pan with a turbo 350 automatic trans.,it is part of the floor,if it has a turbo 400 automatic trans,or a 4 speed manual trans it will have the high hump pan and it is bolted in...

[DBear]

Originally Posted by El Dorado Jim

If it is a low hump pan with a turbo 350 automatic trans.,it is part of the floor,if it has a turbo 400 automatic trans,or a 4 speed manual trans it will have the high hump pan and it is bolted in...

Is this so on a 1978 model? I can't find any Rpo code for Th400 trans in the factory books unless I am just missing it. I couldn't imagine them not offering the 400 in the big crew cab's especially with the big block

[Titomars]

Originally Posted by DBear

Is this so on a 1978 model? I can't find any Rpo code for Th400 trans in the factory books unless I am just missing it. I couldn't imagine them not offering the 400 in the big crew cab's especially with the big block

The RPO code is M40 for the TH400. In 78 all big blocks got a TH400 when opt'ed with an automatic.
By the way I am not saying its written in stone but in all my years I have never seen a C series with automatic come with the high hump. K series is different since a transfer case is involved.

[donut]

Want to know for sure? Post a pic of the hump, someone will identify if it's low or high.
Bolt in? Crawl underneath with a flashlight, look up past the trans at the tunnel, see the backside of bolts? If yes, bolt in. If no, weld in.

We can guess what you have, you can tell for sure.

[DBear]

I understand that but the truck is New Mexico and I am in Texas. Won't have the truck here until next month. Thanks

[donut]

Then unfortunately I can't give an answer. Not sure anyone can (esp if a PO got to it).
FWIW, my C-30 is low hump, welded.

[El Dorado Jim]

Originally Posted by Titomars

The RPO code is M40 for the TH400. In 78 all big blocks got a TH400 when opt'ed with an automatic.
By the way I am not saying its written in stone but in all my years I have never seen a C series with automatic come with the high hump. K series is different since a transfer case is involved.

You are probably right, I was thinking about 67-72 pickups....

[KrazyRay]

I have dismantled 100's of these trucks. There are several different high humps. 73-80 2wd 4 speed, 73-80 4wd, 81-83 2wd 4 speed, 81-83 4wd, 84 up is part of floor and not bolted in. Any automatic 2wd will be a low hump.