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TH400 in place of 700R4

DavidB

DavidB

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I want to replace the burned 700r4 in my blazer with a 400/205. I have a 400 in my K30 with unknown miles or condition. I have a 400 out of a CUCV that had 11k miles on it and then engine blew, been sitting since. Should/can I just check/replace the seals?
 
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you can have it checked out by a transmission shop though i bet they will say it needs a rebuild ($$$) but i'd throw it in and see if it works if it isn't a dd. also, remember with the 205 and th400 you will need to extend/shorten your driveshafts since they are different lengths.
 
habitatxskate said:
you can have it checked out by a transmission shop though i bet they will say it needs a rebuild ($$$) but i'd throw it in and see if it works if it isn't a dd. also, remember with the 205 and th400 you will need to extend/shorten your driveshafts since they are different lengths.
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Driveshafts no prob.

I'm thinking the seals gotta be dried up... what do they have for seals, and what's it take to change them? Shop told me $100 to change them. I'm the foreman at my family's machine and weld shop, so I could prolly do it, but I have no experience with 'em. I'm not interesested in taking the 400/205 in and out twice if the tranny is no good.
 
DavidB said:
Driveshafts no prob.

I'm thinking the seals gotta be dried up... what do they have for seals, and what's it take to change them? Shop told me $100 to change them. I'm the foreman at my family's machine and weld shop, so I could prolly do it, but I have no experience with 'em. I'm not interesested in taking the 400/205 in and out twice if the tranny is no good.
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Replace any input/output seals and any that would be hard to get at once its in. Easy to do and they are cheap.
 
i just dug up my service manuals my cousin gave me..:D

im under the remove and insepct section the only problem is there are 9 pages of info that i can't summarize like i wish i could.:mad:.im not that big of a help since i'm no good with transmisisons what so ever, couldn't even tell you how they work..either way if you have an idea on what may be wrong i can look it up and take a couple minutes and type..

i wish i had a scanner. :doah:
 
The CUCV Th400 might not have the same output length as Th400 did for older 205's. You will need to check that. Most CUCV's came with 208's.

Harley
 
Hossbaby50 said:
The CUCV Th400 might not have the same output length as Th400 did for older 205's. You will need to check that. Most CUCV's came with 208's.

Harley
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I thought about that after I posted this. I know that full well. Rest of you shoulda have caught it too. :D Forgetful us...looks like the K30 is gonna get running to test it's 400 before I yank it for the K5.
 
I have a step-by-step TH400 video on DVD I might be able to hook you up with. :grin:
 
Got the 400/205 out of the K30 and the 700/208 out of the K5. The converters and flexplates are different.
350/700 is 6 bolts on 11", 454/400 is 6 on 11.5". What do I need to do?

TC won't swap over will it?

I have a 6.2 400/TC - is it 11" or 11.5"? Measure tomorrow...NOPE - 11.5"

I could modify the 350 TC I suppose. Machine shop and all...

Will the BBC flexplate fit the SBC?

I have a TH350 but no flexplate. Will the the 350 TC fit the 400?
 
I swapped the Th400 in about a month ago. It bolted in without having to change my flexplate. The flexplate that was on my motor was double drilled so it worked with both converters. The 700R4 used 3 holes that were a little closer together. The TH400 used 3 different holes that were spaced slightly larger.

Harley
 
Hm, my 400 TC has 6 bolts. I'll check and seee if the plate has 2 diff patterns. Rather use all 6 bolts...
 
Had a dual pattern. Got it in. Anyone know which of the 4 wires in the plug from the 700R4 I can use for the down shift wire on the 400 or...?
 
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