swapping automatic trans. to manual with 4wd

[|ow|ife]

Hi Guys,

I am going to go look at a 75 Blazer that has a factory 400. The owner wasn't sure what transmission was bolted to it, but it is an automatic and is starting to slip. Now, I would prefer to swap in a 3 speed manual if I were to buy this truck. And I know that since it's a 400 (not a 402) the motor is an SBC, so the 3 speed would bolt right up.

The only thing I don't know is how the transfer case figures into the equation. I've always worked on 2 wheel drives. I know some modern trans integrate the transfer case into the trans, but I also know that people like to put TH400s into trucks with 4wd so I am thinking the Trans cases are stand alone units here

My question is this: Does the 4wd capability affect what transmissions I can swap in? And btw, this is a pic of the potential new project--owner wants $850 firm

[68Timber]

An SM465 should be a bolt in, the 4-speed w/granny low. You'd have to have the correct adapter for the xfer case in the truck, but you can get them on ebay pretty easily.

[Keith Seymore]

Originally Posted by BRUISER

An SM465 should be a bolt in, the 4-speed w/granny low. You'd have to have the correct adapter for the xfer case in the truck, but you can get them on ebay pretty easily.

well...plus, you'd have to hand the clutch pedal and associated hardware, which makes it a little bigger deal....

K

[68Timber]

I figured he knew he'd need the third pedal. I've got everything to swap one into my 85, still on the fence though.

[Berg]

Thats a pretty good deal, I'd jump on it! The SM465 4 speed manual is considered by some to be a 3 speed with granny low since 1st gear isn't synchronized. It was a factory option in these truck. Your best bet is to replace the transmission and transfer case as an assembled unit since the case that is currently in the truck is most likely going to be 27 spline input. The early Muncie SM 465's used a 10 spline input shaft with a 10 spline output shaft and required a collar to adapt it to either an NP 205 gear driven transfer case or an NP 203 chain driven full-time case with a differential built into it. In the early 80's GM made both the transmission and transfer cases stronger by eliminating the 10 spline output and going to a 32 spline which is much stronger. It also drastically reduced slop caused by wear from the coupler. TH400 automatic transmissions used the same 32 spline transfer cases as the later 4 speeds. In 1985 GM started using a hydraulic slave and master cylinder externally mounted on a bellhousing. From 1973-1984 this body style truck had a mechanical clutch linkage. If this Blazer has the original transmission it is most likely a TH350. You need to get the right adapter to bolt the transmission and transfer case together. If you have a 203 case this is also a good chance to upgrade to a 205. Cutting the hole in the floor for the shifter is no big deal either since the transmission tunnel unbolts out of the truck.
Make sure you get an externally balanced 168 tooth flywheel for an 11" or 12" clutch. The SM 465 uses a larger bellhousing with the Chevy bolt pattern but it has a larger hole for the input bearing retainer. A standard car bellhousing can be opened up by a machine shop but these things are a dime a dozen out there and really shouldn't be modified unless you really need to.

[bmchevy1979]

only thing I dont see mentioned is that the 400sbc is an externally balanced engine so in order to make it right you either have to have a counter weight that goes in between the flywheel and the crank or have the correct flywheel for a 400

Counter weight
http://www.ebay.com/itm/New-SBC-Chev...9ffbee&vxp=mtr
Flywheel
http://www.ebay.com/itm/New-Flywheel...6548d7&vxp=mtr

[84 400]

I did the swap 2 years ago and have since replaced the transmission again... It is a heavy trans so make sure you have one that was known to be good. I did the swap in a 77 k10 so Everything except you needing the 400 specific flywheel should be the same. I actually just make a vid for some guy on youtube and it might help you too. Keep in mind I opted for the hydro clutch because I wheel this truck and the Z bar can pop out and kill your leg after a day on the trails.


If you don't already have an np205 transfercase swap that at the same time. you will need a longer drive shaft and shorter shaft but you get gear drive transfercase.

Also Go for the 12 inch clutch.

[84 400]

here is the auto to stick vidvid link Kinda shakey but you get the general idea

http://www.youtube.com/watch?v=5LERy...ature=youtu.be