Converting a 4 speed to an automatic

[VileZambonie]

yup, fairly straight forward just not all put together in one box which can be confusing if you aren't sure what you're doing. their stuff isn't really always made for the do it yourselfer only because they give conflicting dataif you are using multiple pieces like you listed. That throws a lot of people off. So if you are even remotely impatient skip the trans go if you are doing it yourself. If you feel confident then go for it!

[Mike Phillips]

Mike, I did this swap several times.

Hi Lorne,

Thanks for you suggestions on my swap, Here's where I'm at... the 700R4 has been completely rebuilt and is ready to bolt in, I'm waiting for some flywheel bolts to arrive from NAPA to bolt the new flywheel to the back of the crankshaft first.

After the transmission is bolted in and secure I'll be almost ready to bold the NP208 Transfercase up to it, this is the transfercase that came with the transmission out of a 1985 Blazer 4x4

I have both crossmembers, the original one that came with my 1975 Blazer (which had a 4-speed and NP205 transfercase), and the crossmember that came out of the 1985 Blazer that went with the 700R4/NP208.

From your experience, (and please, anyone else feel free to add your 2-cents), which crossmember should I use/modify to work in my 1975 Blazer.

They are both very different, here's a picture, the top crossmember is out of my 1975 Jimmy, (bolted to the NP205), and the crossmember in the bottom of the picture is the crossmember that came with the NP208 out of the 1985 Blazer.




Also, does anyone have a part number I can use to order the below gasket which fits between the NP208 Transfercase and the adapter?  I removed the adapter to replace the input seal and while I could make a gasket to replace the old one, I would rather buy one that is ready to go.





Thanks ahead of time for everyone's help... need to get this Jimmy back on the road.

Mike

[VileZambonie]

Mike, make sure you remember to remove the pilot bearing/bushing from the back of the crankshaft.

As far as the crossmembers go use the lower pictured one. The other one was prone to cracking and I've personally had them break in half. One while I was driving down the highway in my 84 K5.

I'll see if I can find the part # on that gasket.

[Mike Phillips]

Part of me is wondering if what I should do is have my Transmission Tech, modify my 700R4 and my NP205 Transfercase to mate together and then use this "System" for my Blazer and skip the aluminum cased NP208.

NP205 Transfercase while it was still in the Jimmy
http://www.showcargarage.com/gallery/files/1/1975Chevy4x4RunningGear001.jpg

I'm just guessing but from reading it looks like this is the adapter my Transmission Tech would need?

https://eshop.advanceadapters.com/commerce/ccp1192-28p-n-50-690629-gm-700r4-to-10-spline-np205-coupler-50-6906-50-6906.htm


What I'm trying to do is do this right the first time and end up with a bullet-proof system the will give me years of trouble free operation.  At this time I don't plan on selling the Jimmy and would rather do things the right way and the best way to start with.

Modifying crossmembers, modifying drive-lines, modifying shift linkage, etc. etc. etc.  is okay, but I really only want to do this once.

I installed a 2-Ton Military Transfercase in my first 4x4 and after 12 years of hard driving never had a problem with it, the tranny, the big block Chevy engine or the drive-lines and u-joints.

[Mike Phillips]

Mike, make sure you remember to remove the pilot bearing/bushing from the back of the crankshaft.

As far as the crossmembers go use the lower pictured one. The other one was prone to cracking and I've personally had them break in half. One while I was driving down the highway in my 84 K5.

It looks like the lower crossmember will have my transfercase sitting higher in the frame?  AT least it looks that way?

[VileZambonie]

I'm sure you'll get many different opinions on this but I like the 208 better.

[Mike Phillips]

Mike, make sure you remember to remove the pilot bearing/bushing from the back of the crankshaft.

Thanks for the tip, for my benefit and for all those that read this thread into the future, can you share with us why this is important?

(I'm guess so it doesn't come unglued and throw parts of itself all over the inside of the transmission where the torque converter is)

I'm assuming the best/easiest way is just to Billy-Bob it out with a screwdriver?

 

[VileZambonie]

It will interfere with the installation of your torque converter. The nub on the converter housing fits into the back of the crankshaft to support it. It can't do this with the bushing in there. You can remove it several different ways. 1 use a piloy bearing puller. 2 use a slide hammer. 3 cut it with an air saw and pull it out piece by piece. or 4 pack it with grease and make a punch that fits inside the hole with very little clearance. Smack it in there with a hammer and the grease will push it out. Make sure if you chose this method to wear gloves and safety glasses because high pressure grease squirting out can be painful.

[Mike Phillips]

Thanks,

I'll run down to Autozone and see which of the tools you listed they have I can rent or purchase to remove the pilot bearing.

[Mike Phillips]

Mike, make sure you remember to remove the pilot bearing/bushing from the back of the crankshaft.

Okay, used a  "Blind Hole Puller" to remove the Pilot Bearing, took to steps using a smaller puller followed by a larger puller.  I can see some kind of ridge or lip inside the opening, is this part of the crankshaft casting or some parts of the pilot bearing still stuck in there?

Here's a pic...

[VileZambonie]

That whole round silver piece is the pilot bearing although it doesn't look like yours would really interfere with the converter from the pic there. Best to remove it anyway at this point.

[Mike Phillips]

Shazam!

Third try worked like a charm, when to the third largest spread puller and expaned it all the way then used the slide hammer to convince the Pilot Bearing outer case to come out.  Vacumned the dirt and metal particles out of the hole and now we're off to take the rented tool back to Autozone.

Thanks VileZambonie!   

[HAULIN IT]

Mike, I'm not sure about using the lower crossmember with the 205. I agree looking at just the crossmember, it looks like the transfer case would be higher, but maybe the mounting plate makes up for it? The ones in my trucks look like the Right half of your top one, basically flat (a little step w/gusset plates on both ends). The mounting holes (at the crossmember) are different width on the 205 than the 203 & also I believe on the 208, but that my be incorrect, I'm not that familiar with the 208. I have always liked the 205 myself, but many guys are getting plenty of good service out of the 208. The adapter kit isn't bad money, but I guess you have to alter your driveshafts when using the 205 in this case. I think that is the way I would go. The 208 would be a bolt together deal, shafts & all so that is appealing. Talk to you later, Lorne

[Mike Phillips]

The mounting holes (at the crossmember) are different width on the 205 than the 203 & also I believe on the 208, but that my be incorrect, I'm not that familiar with the 208.

Measuring the width between the mounting holes for the 205 and the 208 I can confirm they are different, we'll measure and post the difference for posterity.

The 208 would be a bolt together deal, shafts & all so that is appealing. Talk to you later, Lorne

We're going to install the 208 at this point in time.  We'll clean up the 208 crossmember today and then do a dry run to see how it goes just trying to place the crossmember by itself into the frame to check for fit.

Thanks for chiming in...

[Captkaos]

I was thinking the actual mount would swap on the Tcases...
There is nothing wrong with a 208 in my opinion, either tranny is fine.  Crawler guys want the 205 to use as a doubler...