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1980 TA

  
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1980 TA

 
patton patton
New User | Posts: 3 | Joined: 11/08
Posted: 11/27/08
07:51 AM

i need to replace the tired old 301/ 350 drivetrain. I was given a a 1975 pontiac 400/th375, is this drivetrain worth the task. Keep in mind this has to be a economy build. Thanks to all.  

hotrod75_ hotrod75_
New User | Posts: 1 | Joined: 11/08
Posted: 11/27/08
05:42 PM

I did a similar swap in 1989 and had no problems at all. The motor mounts fit and was able to use pretty much everythig else to put it in.In fact I left the tranny in and just changed out engines.  

barneyformula barneyformula
Addict | Posts: 3306 | Joined: 01/07
Posted: 11/28/08
04:13 PM

Patton, it's a relatively easy swap.The 400 bolts in right in place of the 301 using the same mounts and wiring. The accessory brackets and belts will have to come from the 400 or another tall deck Pontiac V8 (pretty much all except 265/301) of similar vintage. The th375 trans will work if it is the same length as the th350, if it longer, you are better off having the th350 rebuilt, that way you won't have to shorten the driveshaft to make it fit. You may have to find a 400 shaker assembly, some say the 301 setup fits, but theoretically the difference between the deck height of the 301 and 400 should make the 301 setup sit too high and cause hood clearance problems. If keeping the stock exhaust, you will have to change the crossover pipe to a late 70's 400 part, otherwise duals can be made for your stock manifolds. Check prices first, when I did the 350 Pontiac installation in my 79 Formula, there was no exhaust on the car (stock or otherwise). It was cheaper to have the muffler shop bend up 2.25" duals from the manifolds to the Turbo mufflers and use new 79 TA W72 400 overaxle pipes and tailpipes (with chrome splitters), than it was to buy a crossover pipe, extension pipe, crossflow muffler and the same splitter tip tailpipes. Basically, it was cheaper to get a better flowing and sounding exhaust than the super quiet, restrictive stock stuff. Guess which system I bought!
You will also have to order your parts, such as rad hoses and belts, for the 400, I just tell the parts people I have a 79 400TA, it saves confusion. If the rad is weak, go with a 400 rad, it is the same as the optional HD 301 rad, a 3-row that will easily handle a stock or mildly built 400. Good luck.
Steve  
A little help... 'cause we don't all have to learn the hard way!

patton patton
New User | Posts: 3 | Joined: 11/08
Posted: 12/09/08
07:57 AM

thanks for the reply, but the tranny is the bad part. im thinking i will rebuild the th375 and mate it to the 301 till the 400 rebuild is complete. Im in no hurry. 7 year member of hpp the mag, but never used this before, this is great! keep up the good work. Grin  

mdmBOP mdmBOP
User | Posts: 56 | Joined: 03/08
Posted: 12/09/08
10:30 AM

The 375 is basically a 400 trans with a 350 output (so I was told by an experienced tranny rebuilder). Like Barney stated, if you go with this setup you will have to shorten the driveshaft. If you don't go too wild with the 400 rebuild, the 350 should be able to handle the power from the engine, there are plenty of racers who opt for the 350 because of better power transfer, the 400 is more restrictive because it's a heavier-duty trans. If you're not planning to make monster horepower and torque from the 400 motor, I'd rebuild the 350 transmission and run the 400/350 combo, but when done right the 375 should hold up well behind a mildly rebuilt 400.  
Pontiac, Michigan