1979 chevy 305 engine need trans swap help

[bernie7434]

  I would like to do away with my 3 speed column shift and drop in a four speed on the floor has anyone had any experience with this.  Need to know specs on the 3 speed in the 79 chevys.

[VileZambonie]

What kind of specs are you looking for?

[bernie7434]

i always here about the 700r4 i know thats not it but looking for a name and number for my trans

[Captkaos]

Automatic or manual?  TH350 or TH400 is the auto 3 speed.

[VileZambonie]

yeah are you saying 3 on the tree or automatic column shift?

[bernie7434]

3 on the tree

[bernie7434]

does the th350 have the same length or tail stock as a 4 speed manual floor shift?  also what kind of linkage differences are there in order to swap out the th350 and install a 4 speed.  does the 700 r4 fit?

[werewolfx13]

I'm still confused as to what you want to do..if you have a 3 on the tree, you have a 3 spd manual transmission with a clutch, with the shifter on the column..a th350 is a 3 spd automatic w/ column shift, and a th700r4 is a 4 spd automatic w/ column shift..The most common 4 spd manual floor shift trans that came on these trucks was the SM465..first gear is granny low, and the shift pattern is long and kinda sloppy.

[Captkaos]

^What he said.  Do you have a clutch pedal or just a brake pedal.

[bernie7434]

i have the three on the tree with the clutch pedal and would like to put in a four speed manual trans What is compatible

[werewolfx13]

SM465 is the most durable 4 speed trans offered in these trucks, most people only use 2nd, 3rd, and 4th gear on the street. Is your truck 2wd or 4wd? What are you going to be using it for? Street daily driver, daily driver that sees some off road use, strictly off road rig? Somone else with more knowledge should chime in as to what you'll need to swap a 465 in once we know if your truck is 4x4 or 2x4..

[Fordeatinz71]

yea, he's saying he has a 3-on-the-tree (think he wanted the specs just for giggles)...i've always been told it was the Muncie M15 but research tells me that Saginaw made some too...so your guess is as good as mine. 

he wants to convert to a 4-speed, which is a floor-shift.  you will need to either cut a hole in your existing floorpan or replace your "hump" with a bolt-in hump from a factory floor-shift manual truck.  the clutch workings are all cable, so you will just need to retain your clutch.  the SM465 will bolt into a standard GM housing but the bearing retainer size for the SM465 is massive on the front end, so you might run into a problem there...worst case scenario you have to have your local machine shop bore the bellhousing to the appropriate size.   

the SM465 has a yoked-output so you just have to pop a u-joint in it and you're golden. 

[bernie7434]

the truck is a 1979 305 engine 2 wheel drive 3 speed manual trans on the tree with 54,000 original miles Michigan truck, body is shot but its Grandpas truck, the brakes went out on me a couple of years ago and a train was at the tracks already, had to hit the flasher pole to stop the truck.  it will be used as an every day driver 20 mile to work

[zieg85]

One has to ask why do the conversion at all?  Is your shifter giving you fits.  If so there are quality floor shift conversions out there to do the job.  I am personally looking for a good 3 on the tree shifter/linkage for my 86.  Donor vehicles work best because anything done with the 4 speed (granny) require the remove-able floor hump in a 79 2 wheel drive, at least mine did...  Drive shaft is longer but everything else will work.  There is a 4 speed overdrive trans that is a direct replacement but are very rare to find.  Short tail shaft TH350 is a direct replacement if you want to go to an automatic without driveshaft woes.

[81C10]

One has to ask why do the conversion at all?  Is your shifter giving you fits.  If so there are quality floor shift conversions out there to do the job.

I agree, 3 spd is quite rare, unless you're planning on abusing the truck (off-roading, heavy towing) I'd leave it.