El Camino Central Forum banner

1 - 4 of 4 Posts

·
Registered
Joined
·
46 Posts
Discussion Starter #1
OK im building a 350 that will be a strong street motor and I plan on installing a rebuilt tranny as well. My questions are
1. Is a Th350 a direct fit for the th200 in my 1984 with a 305?
2. How much work is involved in putting a Th400 in?( beacuse I have one sitting in my garage)
I am on a tight budget being a poor 17 year old so a g-force crossmember is out of the equation.
 

·
Moderator
Joined
·
1,867 Posts
The 350th will fit fine. A 350th is all you need unless you build a torque monster & race alot.
 

·
Registered
Joined
·
111 Posts
The TH400 will be a lot more work and expense to install. The crossmember will definitely have to be moved, the driveshaft shortened with a new yoke and an electric kickdown installed. The TH350 will handle most small blocks without too much trouble unless you get really big power and do a lot of launches with it. You might want to check the TCI Transmission website to get info about gear ratios, etc for comparison. The first gear ratios are considerably different in the TH350 and TH400 and will affect your low end performance. Remember, when you check gear ratios to multiply the trans ratio by the rear end ratio to get the final drive ratio to really see the difference between the various transmissions.
 

·
Registered
Joined
·
2,921 Posts
One of the major differences, my understanding, between the 400 THM and the 350 is a center support in the casing. The 400 has one and the 350 does not. The 400 is rated "stock" at 450 Lb. /Ft. of torque (capability) and the 350 is rated at 350 Lb./Ft. of torque stock.

The 700R4 is a better transmission than the 350 THM but still not as good as the 400 you'd have to go up to the 4l80e for that capability in an overdrive. The 700R4 will get you much better gas economy and better off the line starts. So will a 200R4. The 200R4 has the same weakness as the 350 THM though however it has a final drive ratio of .6x:1 and the 350 has a final drive ratio of 1:1.

I would suggest that you install a well built 700R4 you'll have to modify where the cross member sits (5" further back) and shorten the drive shaft by 3" but it is a better transmission and it is a little harder to set up correctly. The 350 has a "Kick Down Cable" and the 700R4 and 200R4 has a TV cable which is not the same as a kick down cable. You will have to adjust the internal pressure using your TV cable.

But then... This is just my opinion.
 
1 - 4 of 4 Posts
Top