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Caddy trany swap ??? Auto-Manual

mudhound72

mudhound72

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OK, this is what I want to do I just need some advice on how to do it.

What I want to do is pull the th400 out from behind my 500 caddy motor and install a np235 manual trans.

I am doing this to a 73 burb 2wd my tow rig

I know I am going to need to make a new drive shaft and cross member witch in no big deal to me.

The biggest prob is the bell housing, clutch and the flywheel, what do I use who has them and/or were can I get them

Someone told me the bell housing patturn is the same as a 6.2 + 6.5l smoker, is this true anyone know

Also what would best for the clutch to make it work as for peddles. also if you have the parts let me know
 
again??

We discussed this in another post not long ago...The caddy has the same bellhousing bolt pattern as pontiac,buick,and oldsmobiles..the 6.2/6.5 deisels have the same pattern as any other CHEVY motor--ONLY a 5.7 "olds" diesel from 78-81 would share the caddy bolt pattern as far as diesel..

The main problem putting ANY manual tranny behind a caddy is the fact they never were designed for one(no caddy ever had a manual tranny factory!)--so GM never bothered to drill the crankshaft for a pilot bushing--It CAN be done,but its a lot of work,to do it right requires the crank to be pulled and put in a lathe!--then the flywheel is the next dilema--a custom made one for about 300 bucks is nessasary...one can be had at www.500cid.com ,along with much more info on swaps....

A bellhousing from a manual tranny equipped buick,olds,or pontiac will bolt on,but the SM465 tranny has a larger "hole" in the center than the 3 and 4 speed muncie and saginaw trannys did,so you'd have to have it hogged out to fit at a machine shop....more $$$$....

I'd think it would be much easier and less expensive to buy a 70 dollar bellhousing adapter and use a TH400 4x4 tranny with the chevy bolt pattern,or a buick,olds,caddy,or pontiac TH400 "short tail" tranny with the 4x4 output shaft installed in it...it all bolts together with factory parts...you can bolt up a TH350 if you use a TH400 converter--the caddy flexplate only has the TH400 converter bolt pattern drilled factory...

You'll have enough fun finding the rear sump oil pan,and fabbing motor mount pads,and all the other things nessasary to get the caddy motor in there--putting a manual tranny behind one is expensive,a lot more complicated,and I personally dont like the idea of drilling a hole in the crankshaft on a torque monster like a 500 caddy..I'd be fearful it would make it likely to crack...but it has been done,whether its worth all that is questionable--be a lot easier and cheaper to stick with a big block chevy motor in a way... :crazy:
 
The thing about this is allready has the 500 Caddy motor in it :cool1: and also has the th400 in it

The thing is that I cannot stand pulling with a auto (the main purpose of this burb is a tow rig) I have never had much luck with them in the past. The tranny works ok but the shift points suck for pulling. I would much rather spend $1000 on a manual setup that I will not break, then get a trany that can.

I do like the info that you gave me it is helping pointing me in the rite direction.

Todd
 
Good info..

Thats very interesting!--I think I'd rather shorten the tranny input shaft rather than drill the crank though--why risk weakening it(or the possibility of drilling too deep!) if its only to provide some clearance for the shaft when its easier to modify the shaft of the tranny..I've never had my 500 caddy motor and TH400 separated yet,so I didnt know exactly what the back end of the crank looked like,but I assumed it had a "hole" for the "button" on the torque converter like any other GM..not too hard to make an adapter pilot bushing..
I suppose both ways have their pro's and cons...and either way works..

It still needs that costly special flywheel though,and a blowsheild(which still might need to be "opened up" to fit the SM465 trannys larger size collar around the input shaft)...but its definately a better alternative than the automatic flexplate with a manual flywheel bolted to it I read about here recently! :yikes: :eek: :eek1: ..dunno if I'd wanna ride in that rig!.. :blush:
 
you could always put a full maual valve body in the tranny then you have full control of the shift points and it would be a lot quicker and cheaper than swaping in another tranny
 
You know I did mention it was really farmered when I posted about the flexplate and flywheel combo....but I gotta admit it scares me too. Sometimes people get creative when they are engineering (farmerizing) things :grin:
George
 
How do the Caddy vs. Chevy crank bolt patterns compare? Does the Caddy use a balance weight?

Four of the six bolts are shared on the Chevy & BOP bellhousing patterns.

My idea is to cut a 1/8" plate to act as an adapter. Use a SBC flywheel, 1/8" thick flywheel "washer/spacer", iron bellhousing, and the b/h-mounted starter.
 
u2slow said:
My idea is to cut a 1/8" plate to act as an adapter. Use a SBC flywheel, 1/8" thick flywheel "washer/spacer", iron bellhousing, and the b/h-mounted starter.
Click to expand...

I have seen a 350 olds bolted to a chev th350 using a adapter plate like that the bottom 4 bolts line up and the top two had a plate.

I am liking the idea of cutting down the input shaft allot better sence it is just in the way.
 
Caddy only...

Only a Caddy flexplate has the right bolt pattern for the caddy crank--no other make will even come close--thats why the "custom" one from MTS (www.500cid.com) is needed...I think its worth 70 bucks to buy the adapter from summit or jegs rather than make it yourself(unless you work at a machine shop or something)...

I'm not sure but I THINK the caddy motor is internally balanced..don't quote me on that though...

I still think the TH400 is the best altenative--much easier,cheaper,no "cobbing" things together,and its about as reliable as an automatic tranny can get..not to mention much easier to drive...sounds like a lot of blood,sweat,and tears just to put a manual tranny behind one..I'd play with the govenors shift points,or use a manual valve body as already suggested if I didn't care for the shift points.. :crazy:
 
Got a price list going right now for the parts that I need so far:

Flywheel $389.00 plus shipping :yikes: Take 3 weeks to make

Bell Housing Think I found one for $50

Bushing $25

Clutch $250

I still need to find the pettles and linkage

So far it will cost me about $750

So far the wallet is not hurting to bad yet :cool1:
 
I found one for a 455 olds and I am going to see if it will bolt up then I will need to open up the center some
 
mudhound72 said:
I have seen a 350 olds bolted to a chev th350 using a adapter plate like that the bottom 4 bolts line up and the top two had a plate.

I am liking the idea of cutting down the input shaft allot better sence it is just in the way.
Click to expand...

Maybe I missed something so ignore this if I did. Cutting down the input shaft to avoid the drilling of the crankshaft?? You HAVE to support the front of the input shaft in a bushing or bearing.
 
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