Trans / T-Case Combination Help - The 1947 - Present Chevrolet & GMC Truck Message Board Network

GMC Trucker · 02-20-2010, 02:28 PM

Hope you guys can give me some help with this...

I have a 1980 Step Side that currently has a T350/203 combo in it. I also have an SM465/205 sitting on the garage floor. There is a guy near me selling an SM465/208 and a T400/205.

My goal is to put the SM465 with a 203/205 doubler behind it into the step side. Other than finding a factory SM465/203 adapter, I know where to find what's needed including the input and output shafts.

Or do you guys think I'd be better off with the T400 and a 203/205 doubler? I'd need to have the face of the 203 drilled to fit the T400/205 adapter and an input shaft for the 203, or find a factory T400/203 adapter and input/output shafts for both.

Thoughts?

Trucker

sierra4x4 · 02-20-2010, 04:29 PM

What engine are you useing? What axle ratio and tire size do you have? Are you planning on useing your truck for rock crawling is that why you want a doubler?

GMC Trucker · 02-20-2010, 04:58 PM

Quote:

Originally Posted by sierra4x4

What engine are you useing? What axle ratio and tire size do you have? Are you planning on useing your truck for rock crawling is that why you want a doubler?

The truck has a 350 now. I have a short block that's getting stroked for it.

The axles have 4.10 gears with 35s. I want to go up to 37-38 to get a little more room until the 14 bolt.

As for the doubler, yes, I want to do some rock crawling with this truck. It'll also be getting used on construction sites. The SM465/203/205 combo with 4.10's should give a final reduction of around 100-105:1 if I did the math right. Quite steep, but I have plenty of ratios to pick from, and easier to get moving with the manual gearbox.

I don't really want to change the axle ratio, or I'll need to put in an overdrive for the highway.

sierra4x4 · 02-20-2010, 10:59 PM

I think you will be just fine with a 465/208 combo. I ran this before and rarely even needed low range becouse the 465 has a real low first gear as it is. I currently run a 465/205 with a 454 and 3.73 and use it for mostly off road and I never use low range I find that the engine just revs out to quick and you need to shift. In high range I mostly use second gear. But if I,m climbing a real steep grade then I will use first gear. If you have a torquey engine you won't need really low gearing.

GMC Trucker · 02-20-2010, 11:12 PM

Thanks for the help Sierra. I can always shelf the 203 for now and put it in later if I do want it.

Cheers,

GMC Trucker

02-20-2010, 02:28 PM	#1
GMC Trucker Registered User Join Date: Feb 2010 Location: Airdrie, AB Posts: 11	Trans / T-Case Combination Help Hope you guys can give me some help with this... I have a 1980 Step Side that currently has a T350/203 combo in it. I also have an SM465/205 sitting on the garage floor. There is a guy near me selling an SM465/208 and a T400/205. My goal is to put the SM465 with a 203/205 doubler behind it into the step side. Other than finding a factory SM465/203 adapter, I know where to find what's needed including the input and output shafts. Or do you guys think I'd be better off with the T400 and a 203/205 doubler? I'd need to have the face of the 203 drilled to fit the T400/205 adapter and an input shaft for the 203, or find a factory T400/203 adapter and input/output shafts for both. Thoughts? Trucker __________________ And now, a word from my lawyers... This post is the intellectual property of the person commenting under the pseudonym "GMC Trucker". These posts are for entertainment only. Copying or quoting in whole, or in part, is given free license for use by any member of this board for use on this board. Any use, in whole or in part, for reference outside this forum requires the express written consent of its author.

02-20-2010, 04:29 PM	#2
sierra4x4 Registered User Join Date: Jan 2009 Location: Canada Posts: 308	Re: Trans / T-Case Combination Help What engine are you useing? What axle ratio and tire size do you have? Are you planning on useing your truck for rock crawling is that why you want a doubler?

02-20-2010, 10:59 PM	#4
sierra4x4 Registered User Join Date: Jan 2009 Location: Canada Posts: 308	Re: Trans / T-Case Combination Help I think you will be just fine with a 465/208 combo. I ran this before and rarely even needed low range becouse the 465 has a real low first gear as it is. I currently run a 465/205 with a 454 and 3.73 and use it for mostly off road and I never use low range I find that the engine just revs out to quick and you need to shift. In high range I mostly use second gear. But if I,m climbing a real steep grade then I will use first gear. If you have a torquey engine you won't need really low gearing.

02-20-2010, 11:12 PM	#5
GMC Trucker Registered User Join Date: Feb 2010 Location: Airdrie, AB Posts: 11	Re: Trans / T-Case Combination Help Thanks for the help Sierra. I can always shelf the 203 for now and put it in later if I do want it. Cheers, GMC Trucker __________________ And now, a word from my lawyers... This post is the intellectual property of the person commenting under the pseudonym "GMC Trucker". These posts are for entertainment only. Copying or quoting in whole, or in part, is given free license for use by any member of this board for use on this board. Any use, in whole or in part, for reference outside this forum requires the express written consent of its author.



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