i am going to run the 300 6cyl. i have mentioned before. But i haven't decided on the tranny yet. C-6 or NP435. I can build either of them but I was wondering if the C-6 would take to much power away from the six cyl. Any help would be appreciated.  

If it were me I'd run the C-6... why.. because... thats its.. lol

I can't really back up my claim because I don't know much about the MP435 but I do know about the C-6 and have full faith in it as a outstanding trans...

Not sure if that helps, but what the hey.  

Oh, and 6+6=12... BTW... lol  

I run a NP435 in my Bronco II and love it. Practically indestructible. The 6.68:1 "granny" 1st gear is nice off road. I have often found myself wishing I had another "street gear".  

I hear the NV4500 is a tough manual with a nice low ratio first gear and an overdrive. No personal experience with it though.

I don't have any experience with the C-6, but hear it's very strong too. Really it just depends if you want an auto or manual.

87 Bronco II
5.0 HO (fuel injected)
NP435 4-speed
NP205 all gear drive transfer case
Dana44 front (full width)
9" Ford rear (full width)
Roughly 9" total lift
35" Pro-Comps MT's on Eagle Alloys  

A NP435 ranks with a SM465 as one of the best trannies of their type. They were great in there day but if I was building today it would be with a NV4500. You use a tranny for its "ratio" range and a granny gear extends that range. A NP435 has a range of 6.56 (lowest divided by highest gear) but a modern NV4500 with a 6.34 first gear and a .75 OD has a ratio range of 8.45. What this means is if you use one of these trannies and gear axles properly you can have the same cruise RPM in top gear as 4 speed but have a much deeper effective ratio in first because OD tranny lets you run even deeper axle ratios with decent cruise RPM's. Just need to stop looking as OD tranny as OD tranies and start looking at them as 5 speeds and fully using all speeds.  

The C6 is really for a big block V8. If you want an automatic, then look into the C4. I would use the NP435 for the granny gear. And if you want the extra gear for hi-way speeds, look into the overdrive kit. I remember seeing one on ebay for $350.  

one of the biggest dilima's I had when building up a manual tranny was finding the right cam set up with a really flat broad torque curve. I ran a 268hyd that ran well but I always wanted more. check into clifford racing for more good parts. That cam dropped off around 5000 rpm. later went to a solid cam with a little more duration helped out a lot. factory fuel pump was border line and later upgraded to holley blue electric.  

I just bought a dead 84 Bronco (fullsize) that Im bringing back to life. It was owned by my brother-in-law's dad. They're kinda gearheads and know their way around cars and trucks pretty good. The Bronco has a C6 tranny and 300ci 4.9L Inline six stock and Im debating on keeping the six since I want to run 44" Boggers through rough sloppy mud. My brother-in-law assures me that the truck is a strong contender the way it sits with 33x12.50's under it. He swears it pulled him through some pretty rough situations and only got it stuck once on the frame. Its gonna get tested real soon so I'll post the results of my crime and punishment after August 10th. If you research the tranny online you'll find plenty of positive feedback on its rugged capability.  

BTW Im looking at buying an NP435E for my Bronco with an NP205 Transfer case for those 44" Boggers I plan to install....at least thats the current plan....the C6 is also geared to high for me...2.46:1 in first gear, 1.46:1 in second and 1:1 in third.  

On the C-6 you have to low gear kit the tranny. Tciauto sells these kits but are pricy, lots of info at tci. The converter is your next problem, which one to fit your engine. Also a c-6 uses up some power compared to a manual. The manual with a centerforce dual friction is a awesome clutch but pricy. Also you need to install a roller pilot bearing because your gonna be slippin the clutch to move those tires. On the c-6 your gonna need a tranny cooler the biggest you can get. Also the low gear kit is like a 2.76 first and I heard about a 2.84 but have to check on that. The trick to making a c-6 live is watch your temps and red performance clutches and install a good band internal. I personally run a lowgear kit and love it in a heavy 4wd. Its been about 5 yrs on it and believe it gonna need to be freshened up soon my tranny color changed and had it flushed and filter changed but its doing it again. 6200lb truck with nice bigblock on 40" hawgs. drop me a note if you have any question.  

It is kinda silly to hang on to old trannies like C6's when for the money you can have a modern 4 speed which allows you to run much deeper axle ratios too and get same cruise RPM and that (deeper axle ratios) together with deeper first gear ratios general used in Ford 4 speed automatics will yield low gear performance in terms of effective drive ratio reduction not even remotely possible with a C6.  

Robby gordon run c-6 heavily modified in his race truck. The problem with the newer tranny's is reliability in high hrsp situation, 475 and up. I know how to make a C-6 live but when I talk to reputable company's they say I'm better off with a c-6 in my world with my hrsp and application. The guys that say they can make it work say its gonna cost around 4000 plus dollars. I can do a c-6 for about half or less, simple math. Tranny coolers are key and keep you stall converters down for less slipage, less heat and quality tranny fluid and deep sump pan. Hope thats everything.  

If you can find an NP435 in your local salvage yard. Then buy a dual force centerforce clutch. All this will get you a much, much better set up that you will love and still be way under $2000. With a manual tranny, you don't lose near as much horses. Plus, nothing is cooler than shifting gears while mud is in the air.  

On the 435 new process I've split a few cases. Running high horse 460 and dual friction centerforce. It'll split at the pto door to lower shaft. 4 speeds are expensive to replace/rebuild also. I prefer a c-6 with correct stall converter. If you rollerize you c-6 internally it frees up a lot of friction. The technology is out their just will you pay for it?  

the o.g. bigfoots were running with a c6 so they cant be that bad