Newbie G30 transmission questions...

[johndglynn]

Hi everyone, great site you have here. I am a newbie to the Chevy diesels but not to diesel power - it's the only way to go!

I live in the UK and am in the process of buying an '84 G30-based c-class motorhome with the 6.2. The seller recently had a problem with the trans where, when he pulled away from a stop at roadworks, it firstly would not go into top (3rd), then when at destination about 8 miles later it would not come out of second, then when it did it would not come out of neutral...

It was allowed to cool, sump was dropped and all looked ok, started up, eventually went into gear but when it shifted up into second it stayed there again. A recon box was fitted and all seems fine now, though seller reckons it is changing up slightly later.

So my question to the all-knowing forum is:

How can I tell whether the gearbox that is now fitted is the right one for the job (this also applies to torque convertor)? I am imagining all kinds of problems if the shop has fitted a lesser gearbox or something...want to get it sorted before I part with the cash!

Thanks in advance and hope the question is not too dim-witted! I want to be sure I have my facts right.

John Glynn in Northants, UK.

[Dieselboy]

Welcome to thedieselpage, johndglynn!

One of great things about GM is that they used the same bellhousing pattern for nearly everything. I'm not sure if you're talking about auto or manual, but here's a short list; the first three are automatics and last a manual gearbox.

TH400, TH700, TH350, SM465

The usual suspects for a 1 ton anything are a TH400 or SM465.

Here (http://www.nastyz28.com/transid.html) is a picture guide that is based on the shape of the pan. It will help you to determine what you have.

[britannic]

Here's a great forum for discussing those transmissions and getting informed answers from rebuilders: NetGearHead Tranny Discussion Groups (http://answers.netgearhead.net/ubbthreads.php)

[johndglynn]

Great stuff, thanks guys.

I'm familiar with the 400 'box as my big block Caddys have all had that unit. I have read all about your 4-speed swaps on here and was planning one of my own, but will have to put some miles up on this one now just to make the thing pay. The job cost $2,000, and I'm making a major contribution, as is only fair.

Can I just say that the detail you guys get into completely blows me away more often than not. You are the Diesel Demi-gods! Really looking forward to getting my teeth & tools (and my engine builder buddy's million dollar equipment) stuck into this marvellous old motorhome.

Thanks again!

JG