Instaling SM420 behind 258 - who's done it? - Off-Road Forums & Discussion Groups
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post #1 of (permalink) Old 07-24-2002, 06:47 AM
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Instaling SM420 behind 258 - who\'s done it?

OK, I know the T18 is an easier swap (maybe), but you can't beat the 7:1 1st gear. Plus, I know a guy who has one for sale.
So how hard is it to mate to the 258? Are there adapters available or will the stock bellhousing work (with modifications)?
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post #2 of (permalink) Old 07-24-2002, 08:30 AM
 
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Re: Instaling SM420 behind 258 - who\'s done it?

I don't know about mods to the OE BH to mate with a SM-420, sorry. I kinda remember reading about someone who modified a GM 2.8L BH to adapt a SM-420 to an AMC 2.5L... yes, different but maybe some help is there.
I do know a guy who might be interested in buying your BH if you want to sell it.

Advance Adapters and Novak both make adaptors to fit a SM-420 between your 258 and D300 (full BH and tc adaptor). IIRC - cost is about $400 for each adaptor and OA length will be close to what you have now. AA has buyer's guide and instruction manual available that provide tons-o-information about swaps and what fits where.
Doesn't a Ford NP435 match to your BH? True, not as low first gear and the guy down the road doesn't have one for sale... but that is still one less adaptor to buy.

Novak - http://www.advanceadapters.com/
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post #3 of (permalink) Old 07-24-2002, 09:47 AM
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Re: Instaling SM420 behind 258 - who\'s done it?

Go with a T18, length is identical to what you have now, no new driveshafts necessary. And the first gear is close, 6.32.
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post #4 of (permalink) Old 07-24-2002, 09:50 AM
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Re: Instaling SM420 behind 258 - who\'s done it?

One other thing to consider, aren't 420 parts getting hard to find?
post #5 of (permalink) Old 07-24-2002, 04:43 PM
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Re: Instaling SM420 behind 258 - who\'s done it?

wouldnt you need to run a divorced transfer? that would really shorten the driveshafts and increase the already steep driveline angles.
If you havent already try Novak-Adapt.com

Jesse
post #6 of (permalink) Old 07-24-2002, 11:45 PM
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Re: Instaling SM420 behind 258 - who\'s done it?

get a ford np435 and use a bell housing that had a t176 4speed or a t150 3speed behind it. the np435 will bolt directly to this bell housing.
post #7 of (permalink) Old 07-24-2002, 11:46 PM
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Re: Instaling SM420 behind 258 - who\'s done it?

oh yeah and the np435 has a 6.69to1 first gear too.
post #8 of (permalink) Old 07-25-2002, 09:16 AM
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Re: Instaling SM420 behind 258 - who\'s done it?

Thanks guys. You've given me some options to look at. Don't you just LOVE planning upgrades?!
post #9 of (permalink) Old 07-25-2002, 11:11 AM
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Re: Instaling SM420 behind 258 - who\'s done it?

I hope nobody minds me throwing an additional question into the post here but it is on the same subject, I have a T-176 and was wondering if the NP- 435 was the same lenght as the T-176? And if an adapter would be needed to make it bolt up to my dana 300?
post #10 of (permalink) Old 07-25-2002, 06:20 PM
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Re: Instaling SM420 behind 258 - who\'s done it?

the np435 is longer than the t176. it also requires an adapter to be mated to a dana300.
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