700r4 to th350 NP203 swap

[wesmigletz]

I’m about to swap a 350 SBC and a 700R4 into our 70 Blazer. I’m using the advance adapters output shaft so I can reuse the Th350’s NP 203 adapter.

Can I measure the TH350 length vs the 700r4, and just slide the engine crossmember forward, so I can re-use the rear driveshaft?

If all goes well, we’ll be driving it from Dallas to Long Beach the weekend of Sep 14.

Thanks in advance

Wes

[SeventyOne]

Yes. It's 1-7/8" and it's exactly what I did. (and several others on the board.)

EDIT - wait you're using an NP203 or NP205?? Still in theory you should be able to do it but I just took out a TH350 for a 700R4. the Tcase was still the stock NP205. I also used the Advanced Adapter output shaft so I could mate the new trans to the OE Tcase.

[wesmigletz]

Originally Posted by SeventyOne

Yes. It's 1-7/8" and it's exactly what I did. (and several others on the board.)

EDIT - wait you're using an NP203 or NP205?? Still in theory you should be able to do it but I just took out a TH350 for a 700R4. the Tcase was still the stock NP205. I also used the Advanced Adapter output shaft so I could mate the new trans to the OE Tcase.

Thanks for the feedback. It is a 203. The Blazer had a NOM 400 SBC and a TH350/NP203 in it when I got it. It was originally a 350/SM420 combo. If all goes well, we might be doing a test drive by Sunday evening.

Wes

[Blazerowner]

I would ditch the 203 and put a 205 in. Isn’t a 203 all time 4wd as well unless converted?
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[wesmigletz]

Originally Posted by Blazerowner

I would ditch the 203 and put a 205 in. Isn’t a 203 all time 4wd as well unless converted?
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I'm not sure if they're full time or not. I don't currently have a front driveshaft, or even a shifter for my transfer case.

[BobbyK]

203 is chain driven instead of gears.
The chain is the weak point of that transfer case.
And yes the NP203's are full time 4 wheel drive. All 4 wheels turning at all time. There are kits that convert them to part time like a NP205.

When coupled to a TH350 is has a 27spline output shaft.
When coupled to the manual Sm465 it has a 10 spline.
And a TH400 would have a 32 spline.


Your SM420 should have a 10 spline output shaft.

I know Advance Adaptors have output shafts to adapt just about anything to anything.

I used them for my 350/700R4/NP205nconversion. It has a 27 spline output shaft.

This pic shows a new Advanced Adaptors output shaft (top one) 700R4 to NP205. The bottom one is the same but broken.

[Blazerowner]

I’ve heard the part time kit for the 203 isn’t the best because the tcase is designed to be oiling itself at all times. I had a 203 in the past and when we took it apart the chain was broken. The 205 is a much better tcase. The 203 is heavy as hell as well.

[wesmigletz]

I picked-my 700R4 with the advance adapters output shaft on Thursday. Got the cam broken in and the engine is ready to drop tomorrow (Labor Day).

I moved the engine cross member forward 1 7/8" so I can use the same driveshaft, as others have done on the forum.

BTW, can I drop the engine, trans and transfer case in at the same time with the front clip in place? I'd rather not have to wrestle the transfer case into place while laying on my back.

[BobbyK]

All 3 together would be pretty long.
If the rad and rad core support are out it should go in pretty easy. Otherwise you'd have to almost get it vertical to clear things.

[Blazerowner]

Try removing the cover in the cab and use an engine hoist to put the trans a tcase in. I wouldn’t try to do all three but it’s probably not out of reason.

[wesmigletz]

I didn't see anyway to get the engine, trans, and transfer case all in together. Installed a new engine harness and cleaned-up the headlight harness a bit, but I didn't get the engine dropped today, gonna try again after work one night this week.