Drivetrain Questions and Suggestions

-
Boltmopar

Boltmopar

Active Member
Joined
Mar 18, 2015
Messages
32
Reaction score
8
Location
Moval
So I have a 73 Scamp, and now that my tax return came in, I have some extra money to help move my project along. Currently The car has the original 904 that is mated to the factory 318 with the factory 8.25 rearend. The transmission shifts fine and has started to leak from the front seal or whatever it is called.

So I am going to build a 360 for this car (another thread to come) and not sure which route to take. The 360 I bought came with a 727 from a van, so should I build the 727 or the 904? what is need for the 904 to work with 360 (externally balanced or something right?), and to run the 727 what else do I need besides to shorten the driveshaft.

As for the rearend should i build the 8.25 or a 8.75. my 8.25 currently works and is in the car, but is a non suregrip. I have 8.75 A body housing but no guts. Which one would be better/cheaper to build? What kind of case should I look for for 8.75? This is all new to me. Keep in mind I only have about 1800 to spend on drive train,but plan on doing as much work as I can to keep price down.

Thanks for any input
 
The 8 1/4" axle is a pretty tough unit. If you like the gear ratio you can save a bunch of $$$ and just install a "Powertrax" limited slip diff.
 
The 727 is a more durable transmission but it takes more HP to operate. A mild 360 and a well rebuilt 904/999 is a good combination. The 999 is physically the same in appearance to a 904 except that they were built with a 2.75 first gear. You see, in the early 80s, Chrysler was still a few years away from releasing a real 4 speed automatic with overdrive. Their holdover idea was to use the 904 with a lower 1st gear while equipping the cars with a taller axle gear. This gave the car decent low speed acceleration with a lower cruise RPM. I do not recall the exact year that the 999 model was introduced but I suspect that it was 1980 or 81. One advantage to using the 999 is that your cooler lines, shift linkage and drive shaft that you have now will still work.
I have used these 999 transmissions before. I had a 73 Duster that had a dying 904. I replaced it with a 999 from a wreck and I instantly felt the improved accelleration.
 
360 with the 904 (or 999 if you want to spend your $$ that way) will be a good combo for the street. The 8.25 will also suffice as you are on a tight budget - $1800 will piss away quickly. Also, by using the current trans you won't have to mess with the drive shaft - more $$ saved. How is the 360 you bought? Miles on it? Was it running? etc.. - the usual suspects to start with IF you don't have to get into the engine internals - intake, better carburetor, headers and upgrade the ignition components -better plugs, wires and coil at least. To put the 360 in where a 318 was, you'll probably need different engine mounts. And of course you will need a new torque converter. Add it up and expect the unexpected "other" expenses and - - boom boom boom - $1800 gone. Spend it wisely and you'll do ok.
 
318/904 combo is great for puttering around . We use a modified 904 in our 10 second car . Just needs upgrades . I'm not a big fan of 8.25" axles just because of the limited options of ratios but if that's all you have , use it . When starting a build lots of folks start with the motor which I believe is backwards . Start at the back and work your way forward nont including maintainance . Hope this helps .
 
Thanks for the input I think I may keep the 904 but I think I need a different type of flywheel or something to run the 360 because its balanced differently from the 318?
 
Boltmopar said:
Thanks for the input I think I may keep the 904 but I think I need a different type of flywheel or something to run the 360 because its balanced differently from the 318?
Click to expand...
If you keep the 904 you will need a 360 torque or you need to have the weights welded on the 318 torque.
 
For $1800, up here buys very little, so My suggestion is;
Before you do anything, go out and do some TIMED zero to 60mph runs with the current combo.Do at least three and average the time out. You will need these later to compare to, as your combo gets progressively quicker. After she's been hot-rodded a while you will get used to it and begin to think she is slow.
So this year,spring of year#1
Put a new seal in the tranny, and it is is still shifting good,put it back in.
Then put some 4.10s, plus an LSD, into the 8.75. Sell the 8.25, and buy some big tires. Then call it done. Those 4.10s will get you about 60mph@4800 at the top of second gear.This will be all for this year.In the meantime you can save up.
Year#2,spring
Install headers, a free flowing exhaust and a 4bbl . Put those on there, all together,for another nice boost. These are all things the 360 will need anyway.
Now you are ready for more engine if it comes to that. I say if, cuz those listed items will make a huge improvement in the teeners performance.So start saving for the third spring.
Try not to be tempted to hotrod the teener. For about the same money plus a core, you can have a nice 5.9. This is an instant 13.5% increase in engine size,with an instant increase in across-the-board performance,even stock.
Year #3;
Drop that stock,used 5.9 in there, and freshen up the tranny.Drive it for the summer.
Year#4 saving money; and time to upgrade; the suspension,steering,&brakes, to prepare for the planned performance improvements.
Year #5;saving money; and upgrades to the cooling, ignition, and fueling systems,for the coming bigger engine.
Year #6. build a nice 5.9, and drop that 380hp SBMer in there,as a climax to the program.

Now you have something.
 
You must log in or register to reply here.
-

Back
Top