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72 Z28 12-16-2002 06:53 AM

help with crossmember on th300&th400
when swaping a th350 to a th400 do i need to cahange the crossmember ? If so what other stuff do i need to change .? :eek:

josh7681 12-28-2002 09:13 AM

I have a 69' camaro that had a TH350 in it and I went with a TH400. It is true that a manual and TH350 will use the same crossmember, but the TH 400 will not fit. I had to order a TH400 crossmember (I got it from "THE PADDOCK"). I had to do a little "coaxing" with the subframe holes to line them up with the new crossmember, but it fit great. The only thing that really got in the way, was the pipes. I run a set of Headman full length headers that were bent for the TH350 so it took some more coaxing with the pieps to fit. Been running the TH400 for about 2 years now, and no problems.

racer56 12-28-2002 10:14 AM

You can cut the flange off and weld it to the other side of the same crossmember you already have. That way you don't have to buy anything.

burnout 12-28-2002 09:16 PM

[quote]Originally posted by 72 Z28:
<strong>when swaping a th350 to a th400 do i need to cahange the crossmember ? If so what other stuff do i need to change .? :eek: </strong><hr></blockquote>

burnout 12-28-2002 09:43 PM

[quote]Originally posted by burnout:
[QB][/QB]<hr></blockquote>I agree with those above, but I have done this swap lots of times by simply making 2 extensions of 3/8 steel around 6 in long x2in or so wide drilling them out in 4 places so that they will bolt up to the rear most holes in the sub frame cross member mount area, and bolt the cross member to the remaining holes of the adapter,before drilling,you need to clamp this stuf in place and mark the points to be drilled! worked for me lotsa times and no welding needed... this is not to say that the other ways sugested above aren't xlent, but just a quick trick that worked well for me. best o luck with whatever way ya go!

burnout 12-28-2002 09:49 PM

Joker420 11-11-2003 05:32 PM

TH-400 crossmember
Hi. I have a similar issue. 1977 Pontiac Firebird. Any places I can get a new or used one, or tips about how I can make mine work. Its a 350 crossmember and currently is mis aligning my tranny/driveshaft. Any assistance is greatly appreciated.

68_6cyl_camaro 11-11-2003 10:55 PM

i am doing the same thing right now and bought a new crossmember. I'm probably retarded or something but how the heck do i get my old crossmember out? i've twisted, lifted, slid, smashed, cut, dented, and everyother thing imagineable and can't get it out. please help before a perfectly good camaro gets burnt to the ground and the ashes get pissed on.

Joker420 11-12-2003 02:55 PM

ashes to ashes
Easy Im not the most knowledgable guy with cars, and Im noty trying to call you dumb... Im sure yours is more complicated from what you say BUT mine.... just has a few bolts and it comes right off. And yur not retarded, Im looking to prolly buy a new one as well. Less I can find a good used one or follow the advise of a tech rep and have someone do some welding to make one for me. Prolly just buy the new one to lessen hassle. Good luck bro.

68_6cyl_camaro 11-12-2003 08:39 PM

this is totally rediculous. its unbolted, has free movement front and back and up and down and won't come out. I think i need a bigger hammer.

Joker420 11-12-2003 09:07 PM

LMAO. Im not sure what to tell ya man.....Ill ask around some of my places and see if I can find some better answers for ya. But I guess if all else fails....:smash:

68_6cyl_camaro 11-12-2003 11:32 PM

well, bigger saw, bigger hammer... Now the car is officially no longer a 6 cylinder!!! that crossmember was totally wrong (or at least it looked that way compared to the new one. way too much space around the outside of the bolt holes making it impossible to twist and get out. the new one went in without even straining my little brain.

Joker420 11-13-2003 02:59 PM

Glad to hear it man. Now if I can just fix my lil problem.

brad_irc 11-13-2003 04:23 PM

Today I ripped a th400 out of a box van for my nova, and I'm curious about everything that needs to be done to swap from a th350 to a th400 .. I know that the cross member needs to be changed and moved back 6 inches, but, what about my driveshaft length and yolk ? I've also heard I have to setup an electronic kickdown?

gpeak 11-14-2003 05:36 PM

I've always just taken the measurements that you need, mark where the driveshaft needs to be cut and take it to the machine shop. They will cut the yoke off and the extra material then weld the yoke back on, assuming it's the right size yoke.

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