Auto to Manual Transmission Swap - 72 Blazer

[tjsblazer]

Ok I searched the forum and found a good thread on switching Manual to Auto transmission but not much on going from Automatic to Manual.

I have a 72 Blazer with a 350 engine 350 AT and NP 205 transfer. I want to swap out the 350AT for a SM465 manual transmission. Looking to hear from anyone that has done this. Things that would be helpful.

Is this basically a bolt out and bolt in?
What is the total list of replacement parts I need? (ie. clutch pedal, linkages, mounts, etc, etc.)
How do you know where to cut the hole in the tunnel for the shifter?
What all has to be removed and discarded?
Is transfer case placement the same or do drive shafts also have to change?
Is the cross member the same and bolted in the same location on the frame?
Is the firewall and frame already set-up for a clutch pedal truck?

I understand that it is easiest to swap the transmission and transfer case together as the adapter and input shafts are different but need help on all the rest.

Thanks in advance for any help!

[BigRed Beast]

I'm in the middle of the same swap and posted several days ago. For sure you'll need to change from a low hump to a high hump tranny tunnel. You noted that the spindles are different in the transfer cases, so I'm keeping the tc and 465 together as they came from the factory.

I took out the pedal assembly from our donor--I had to remove the column (which I needed to do anyway) and the steering shaft to slide the pedal assembly out. The donor had the instrument panel already out, and I can't imagine removing or installing the pedal assembly with the panel in place. But, given the interchangeability of everything, I made be able to put the clutch pedal into the existing automatic assembly, so we'll see...

There is a bracket that needs to be installed on the frame/inner fender just under the brake booster to allow the entire clutch linkage to bolt up--the linkage also connects to a ball/stud which threads into a stock engine. The donor has the bracket, but it looks like it's been installed with a round head bolt and nut--there's no obvious way to remove the bracket without grinding the bolts off.

The great thing is that Chevy made everything so interchangeable that there are holes for the brackets, holes in the firewall just waiting to be opened, etc. The modifications, thus far, are zilch.

I'll let you know if the drivelines are particular to each set up, but, having the donor, I really don't care as I can swap the entire set up from the engine back. Plus, as I take things out, I'm rebuilding whatever I remove prior to reinstalling.

I'll post as we get stuff done, but they're calling for snow tomorrow, so I suspect we'll abandon the effort in favor of football, tv, beer and the fireplace...not necessarily in that order...

[tjsblazer]

Originally Posted by BigRed Beast

For sure you'll need to change from a low hump to a high hump tranny tunnel. ...

I was under the impression that all 4wd came with the high hump regardless of the transmission, is that incorrect.

[BigRed Beast]

I'm not a good historian for the tranny humps...but, with the donor truck sitting side-by-side to the driver, the hump for the 4 speed was definitely the high hump vs. the low hump on the auto tranny driver.

[tjsblazer]

Is there any wire harness changes to make? How do reverse lights work from Auto to Manual or any other circuits to consider?

[BigRed Beast]

That's one of the things I'll be addressing as I go--if memory serves , there is one or maybe two wiring items on the manual that, obviously, aren't present on the auto.

At worst, I'll splice, at best, someone here will tell me that there's a Chevy solution in the form of an adaptor. Either way, I don't see it as a big deal.

You'd think I'd learn, though...how many times have I said that!

[cleszkie]

You could always consider just installing a hydraulic clutch setup instead of trying to piece together the original linkage. The bonus is that you don't have to mess with the pedal assembly. Leave the auto pedal assembly in place and just bolt in a new hydraulic pedal assembly with master cylinder (Wilwood or CNC) to your firewall, plumb it to the slave cylinder that you mount to push (or pull) your clutch fork, and you are good to go. No linkage to bind or adjust, just perfect pedal action every time. I've done this several times with great results.

[tjsblazer]

Digging in to this some more. Do I need to change the crossmember? Is the crossmember for the TH350 different than the one for the SM465? Does it bolt in a different place? Also I have the second crossmember and skid plate is that the same for Auto and Manual? Just trying to piece together everything I need. If someone has done this exact swap before could pm me their contact info, I would love to talk to you for a few minutes on some of the details. Thanks to everyone, Jeff.

[yellow70GMC]

You'll need a new transfer case and new adapter. TH350s have a 27 spline output shaft, the 465 has a 10 spline. You might be able to change the input shaft on your t-case, i'm not sure if the bearings are the same size or not.

[1tonblaze]

I did this same swap my self had a auto blazer and a stick shift blazer took everything out of the stick shift , pedals , linkage , steering col , tans and t case . its a pretty stright forward swap if you can get ahold of all the parts . a hydro clutch system from a later model truck would work to get rid of all the linkages and z bar

[tjsblazer]

I am going to stick with the stock clutch linkages. Can anyone verify for me if the crossmember is different and if it bolts in the same location on the frame or not. I've gotten conflicting answers.

Originally Posted by 1tonblaze

I did this same swap my self had a auto blazer and a stick shift blazer took everything out of the stick shift , pedals , linkage , steering col , tans and t case . its a pretty stright forward swap if you can get ahold of all the parts . a hydro clutch system from a later model truck would work to get rid of all the linkages and z bar

[yellow70GMC]

i think you're gonna have to move a crossmember because of the different lengths of the two transmissions. Heres a site with pictures, it might help give you an idea of what's involved. http://www.coloradok5.com/auto2manual.shtml

[70 beast]

i did the same swap in my 71 jimmy and in a 70 gmc.

the only problems that i really had was the z bar frame mount
other than that it was a straight swap. the cross member was in the same spot.
the drive shafts should be the same.

[tjsblazer]

Ok, I think I'm clear about the frame mount now for the Z bar. I see on my frame where the holes are but no brkt. Still unclear about the z bar mount on the engine side. Does it screw in to the block or the bell housing. See in the pic here, if this is the correct bellhousing it is clearly mounted there.


Also, 4x4 tranny x-members are the same and mount in the same location. Is this correct? I think tranny length differences are made up for by the different tranny x trans case adapters, which also means both front and rear drive shafts are the same? is this all correct??

[Burt4x4]

That pic looks nothing like my factory 72 SM465 cast bell...Lemmy look for pics and get back to ya

[sdailey]

The stud should mount into the block not on the bellhousing like the one you have pictured. Here's crappy picture of my sm465 bellhousing for a reference (ignore the colored boxes).

[Burt4x4]

I agree, the ball stud on my 72 was in the block, the pic above you can see the hydro slave mounted to the bell...my realy old pics of the manual linkage is on a diferent harddrive I can't access right now...

[tjsblazer]

Thankyou to everyone on here today. It cleared up a lot for me. The only other thing I am a little worried about is wireharness changes for the steering column and reverse switch ?? Is this going to require harness changes or splicing?

[RideSF]

The wiring is a lot easier than you would think.. I usually jumper the neutral safety switch on the column, you just have to exttend (solder) wiring for your reverse lights..
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