Converting '93 Blazer from IFS to SFA?

[CadillacPat]

Greetings all,
I'm new to this board and joined last week. This is my first post. I'm usually on the caddy500.com board, as I am a Caddy engine enthusiast. Feel welcome to ask me anything about Caddy 472/500's.
I have a '93 full-size Blazer with the following: 5.7, 700R4, NP241, 10 bolt rear with 3.42's (factory posi) and I am thinking an 8.25 front IFS dif. First, the 12 bolt started making noise and quickly followed by clunking. I didn't have another rear, and it was getting near the end of winter, so I simply removed the drive shaft and continued driving the truck. This is because I had nothing else to drive in the winter (my other vehicles are a '98 C3500 low-rider Dualie and a '72 Caddy Coupe which don't go out in the salt/snow). Shortly afterward, the trans only had 1st (the trans had previously ran fine, except for the lock-up torque converter acting up under load-uphill on the interstate at 65 mph). While driving the truck home (about 50 miles) in first gear around 25 mph, the engine spun a rod (the truck had bearing noises since I bought a year previously).
Since I had planned on installing a Caddy 500 anyway, the engine problem didn't concern me. I was also planning on having the 700R4 rebuilt, but I knew it would be marginal at best behind a 500. I looked into installing a TH400, but found I would need an adapter from Novack or Advance Adapters to mount it to the NP241. Not a problem except for the $500 price tag. Building a 400 is much less than a 700, so the slight additional cost is worth the piece of mind of the 400.
Next comes the NP241. I want to use it, but found it really isn't that strong. Reading that it is much better than a NP208 (listings on ebay), I thought it might be. It seems there are opinions otherwise.
So, it appears my best option would be to upgrade to a SFA. Knowing the 14 bolt is pretty strong, I found a 14 bolt 10'5" FF on ebay cheap out of a '98 C2500 (3.73 open). Will it bolt right into my Blazer? Or is the spring mounting a different width? What about converting the axles to six bolt? I had read that a kit is available for six bolt axles for the 9.5" SF version of the 14 bolt. Is there a kit available for the FF 14 bolt? If so, I will rebuild it and install 3.42 gears (the lowest numerically that a 14 bolt can take) and a posi. I also need advice on which posi to use. I'd like to keep the stock 6 lug wheels if I could, but am willing to change as I have to buy tires anyway. What about wheels if I have to convert to 8 lug? The truck will be street driven, with some off road use, and I plan on using 33 X 12.5 X 16 (or 15)'s. I have calculated that this combo will result in a 2400 rpm engine speed at 60mph-perfect for the cam going into the 500.
Next, I need advice on a transfer case and rear. I am thinking I will upgrade the transfer case to a NP203 or 205. What about the front dif? I should also mention that I want at least very good reliability and that I would like to at least try the truck out in the local County Fair truck pulls without it breaking.
Finally, since Caddy engines are known for their torque, the minimum amount will be 600 ft.lbs. at around 3000 rpm using a Potter Automotive/Cadillac High Performance cam.
Any help I could get would be greatly appreciated.

Pat

[CadillacPat]

Oops!. In the second paragraph, the second sentence should read "First, the 10 bolt..."
I also have two 12 bolt housings, one with some parts inside (carrier and ring and pinion, but I never looked to see what exactly-I have them stored at a friends house). I think they are from late 70's/early 80's or 80's Chevy/GM trucks. How would I tell? By measuring the leaf spring perch distance? If so, what else? Thanks, Pat

[CadillacPat]

A few more things. Since I am converting, I will have available a NP241(C?) in good working order and another NP241C that was rebuilt a few years back. Also, the front 8.25" dif slips (not sure how bad it is), so it might be good for at least some parts, but, I also have a spare front dif which worked great before I pulled it from a '95 Chevy 1500 pickup. I think both are 3.42's and non-posi.
Finally, I live in northern Michigan, but will be making a trip to various parts of Ohio in the next few weeks (to pick up the '98 C2500 14 bolt FF).
Pat

[texas sub]

just a few tips, that much torque will probbably frag the 241c, if you can find a np205 or spend a little more and chech out atlas transfer cases, after market transfer cases, i believe that the 2500's are the same width as 1500? and the only other thing would be 3.42s with 33x 12.50. thats alot of presure on the rearend, you might kick it up a little3.73 or more. this is all just advice from some one who helped his son build some big rigs. also don't go cheap on the drivelines, they take alot of abuse. o and you might check out paralel link suspension. good luck!
mike

[CadillacPat]

Originally Posted by texas sub

just a few tips, that much torque will probbably frag the 241c, if you can find a np205 or spend a little more and chech out atlas transfer cases, after market transfer cases, i believe that the 2500's are the same width as 1500? and the only other thing would be 3.42s with 33x 12.50. thats alot of presure on the rearend, you might kick it up a little3.73 or more. this is all just advice from some one who helped his son build some big rigs. also don't go cheap on the drivelines, they take alot of abuse. o and you might check out paralel link suspension. good luck!
mike

Mike,
Thanks for the reply. I was trying to get away from the 241C, but need help with alternatives. The 205 was my first option (durable, cheap, easy to find and I might have one; it or a 203). I had looked at Atlas, but $2k is a little pricy. As far as spring perch width, it looks like the 1500's and 2500's share the same width from '88 to '98. I wondered about stress on gears, but 3.73's will really make the engine spin with no OD, and the big Caddy engine likes to make low-end torque. Still, the cam I will be using will make about 650 ft.lbs. @ 3000 rpm and peak hp @ 4200 rpm (I originally planned on stock heads, but, if I'm upgrading the drivetrain this much, head porting is in the plan). However, the rear I already bought has 3.73's in it, so I just might stick with them and see how the truck runs. Also, since I had thought about lifting the truck about 3", I am also considering 35-12.5's. The front SFA kit I found on Off Road Unlimited features a 3" lift built in. It's pretty reasonable at $699. Now I'm looking for a Dana 60 for the front.
I did some more research last night. I looked around the website for GearTechHD, but couldn't find any prices. Part of my fears were realized. As the old adage goes, "If you have to ask, it costs too much". The bad news is that the 14 bolt FF 6 bolt conversion kit (hubs and axles) is $895. The alternative is to get new wheels in an 8 bolt pattern. The worse news is that the disc brake kit is $1250. Although the kit uses standard '78-'85 Chevy 3/4 ton front rotors and calipers, the rotors have to be machined out about 1/2 inch. Still, that's very pricy for a disc brake kit. There is good news, though. If I use the original hubs, I can then use standard 3/4 ton brakes with no machining. This brings the brake cost to under $400 ($74.95 each for the rotors, $21.99 each for the calipers-but a little more if you want Eldo ones w/ e-brakes, and about $19-$60 for pads depending on which ones from their Valuecraft to Premium Carbon Metalic from AutoZone and about $140 for the weld-on caliper brackets and SS brake line kit-$30 less for rubber lines). 8 lug wheels are the most expensive parts. Cheap ones can be found at Discount Tire for about $100 each. I have Alcoas on my '98 C3500 2WD lowered Dualie (summer truck), and I like them, but a set is about $1000. I'm looking for a compromise.
Finally, there is more good news, from GearTechHD. They have a NP 205 adapter kit w/ a input shaft and bearing for a TH400 for about $525 and another $135-$145 for a TH400 4WD output shaft. I think the output shafts are also on ebay. Besides about 23 Caddy 472/500's, I have 17 TH400's in all three 2WD output shaft lenghts (none are 4WD).
So, I'm still looking for advice (Ford or GM front Dana 60's, NP right or left drop? and driveshafts. And which posi to use. I think Detroit Lockers are out as they lock too much for street driving. They will work however, but you have to be extra careful driving on slippery and/or wet roads, especially on curves. It is looking like the Eaton? What about an Air Locker? The 14 bolt I have is open.
Finally, "parallel link"? Is that like a four link used on cars such as my RWD Caddy? Don't the '69ish GM trucks use it? I remember an article in Hot Rod/Car Craft about installing one in a GM truck-a kit from "Fat Man". It is supposed to greatly improve handling for 2WD trucks (hmmm...I wonder if they make a kit for my Dualie!).

Pat

[texas sub]

hey pat, god to see you are puttin some thought in to this . thats good. asfar as danas i beleive that the ford has a larger ring gear? if you have a 203, check out ord deul tranfer-cases, or fabworks, you'll like it if you like rocks and stuff. i'veheard a lot of good stuff on air lockers and a little bit on eletric lockers. as to the parell link i'm looking for the article that i read, they show a 60's model bronco with a complete set of the 4 link or 5? air bags and ctis. if the wife will figure out what she did with my mags i'll let you know where to look.one other thing that i would suggest is on-board air. let me find those mags, and mabey the tools that i blamed my son for stealing one last thing 16.5 rims can be more trouble than they are worth, ya might go with 17?
mike