I'm still kinda new to the ctd, with only 1200mi on my first one. What gear ratio? tire size? manual or auto? do you guys run, mileage do you get, and how do you use your truck?
I have a 75 f250 4wd with 315/75/16 MTs. I put a 12v and 4spd auto from a 91.5 drw 2wd in it. The motor is a cummins recon motor/pump/turbo that had 6k (according to the seller, who seemed pretty stand up). I am running a full length 3" exhaust with no muffler. Stock air filter, intercooler, did a few minor adjustments to the pump. No tach, pyro, or boost gauges yet. My axles are geared 4.10, and with 35" tires, that is about the same overall ratio as a 30" tire with 3.54s. I'm getting 14-15.000mpg (corrected) mostly highway, some stop and go, ac off. Doesn't seem to make much difference whether I'm easy on it or not. I don't plan to tow any more than 7k with it. If I went to 3.54s would I pick up accelleration and mpg? I'd like to make it a little more fun to drive, and get enough mileage to leave the toyota in the driveway w/o breaking the bank.
Thanks in advance.

I have a '90 CTD 5-speed getrag with 3.55's and 315/75/R16's and I rarely get worse than 20 mpgs with it empty. I haven't towed anything heavy with it yet, just a small horse trailer (probably 2-3k tops) and I still never had to use 1st gear. Mine does fine with 315's and 3.55's. Unless you have the gears already and know how to set them, I personally wouldn't swap them out for 3.55's. My buddy has the same truck as me, but he has 4.10's and 33's. He gets slightly worse fuel mileage than me, but not nearly bad enough to warrent re-gearing. Are you using the TF727? or did you convert it to some other auto? Are you running a divorced t-case? Sounds like an awesome build up, post some pictures!

Chris

EDIT: I've heard (no personal experience) that CTDs take a while to "break-in" and you don't really get the good fuel mileage until a few thousand miles have been put on the engine. This is just hear-say, but you might want to check in to that, maybe some one else can verify this? I think mine is good and broken in at 310k :flipoff2:

It has the 518 overdrive tranny, with a divorced 203 (stock) with the front d/s removed (untill tcase is rebuilt w/new chain).
http://i25.photobucket.com/albums/c70/PROJECTJUNKIE/IM000305.jpg
http://i25.photobucket.com/albums/c70/PROJECTJUNKIE/IM000257.jpg

Thats a work of art! I love how you went sleeper style with it, no emblems or flashy hints to it having a 6BT.

Chris

'93 CC 4x4, auto, 3.55s, 255/85/16s. Average 15 unloaded, 13 loaded. And I don't drive it like a Grandpa, I enjoy it.

since your front d shaft is aleady temporarily removed. you should borrow a set of 2 37" tires and put them on the rear. this will change your gear ratio. drive around for a week or so and see how you like it. i would even go as far as to pull a load with the 37's on. once you do that you can make your decision. you could either keep your 35's and regear or pony up and buy new tires which will probably be cheaper than new gears. 37's w/ 4.10's will make your truck feel like 35's and 3.80 gears. i did this before i regeared my truck.


on another note i used to have a 98 12v cummins w/ 3.54. i kept 2 sets of tires mounted up and would switch them depending on what i was doing. for normal driving i ran 315's and for towing i ran 285's. the 285's were about perfect for towing.

Nice job on the swap, I am also doing the cummins swap, I am using a 98 12v & installign it in a 79 supercab, but I will be running 38" tires with 4.10 gears & an NV4500,

How tight is the intercooler in the front? and what radiator is that?

Thanks nooblet, I was thinking about 3" Cummins sticker on the back window so nobody thinks its a powerstroke.

Jay, how hard are you running it? Any mods? thanks!

Reeser, good thinking on the 37s. I've got a set mounted up for the next truck. It would give me a good feel for the power and I could run them for 100mi or so. I can get an exact mileage with the gps. What kind of mileage were you getting unloaded with the 315s? manual or auto?

Thanks skipped link. The stuff up front was a really tight fit. The next truck (starting with 2wd) will have the motor sitting lower and further back than this one, but I would have had to remove and refab the crossmember under the engine, move the t case, and move the fuel tank that is 1/4" behind the tcase. Then I'd have to pony up for 3 d/s instead of the one. The fan, radiator and ac condensor are from my non IC 89 parts truck. They had extra sheet metal that had to be trimmed to fit the IC into the sides. The ac condensor is sandwiched btwn the hood latch support and the rad. The hood support was seriously trimmed and gusseted, the 91.5 intercooler fits btwn the support and the grille shell (trimmed 1" or so where needed). The intercooler was bowed in the wreck and made it fit a little better :D
Your swap sounds pretty bad ass. The 5spd should be a nice match. I personally wanted to keep mine an auto for DD purposes.

Thanks for the info, My plans are similar to what you have done, only I will be using the 79 4 row radiator, & an after cooler from a 99 PSD, I'm just waiting for the engine, it is in the shop getting freshend up, all the mounting & fabwork is pretty much complete, other than the front clip stuff,
What a/c unit did you use? I see there is no nasty stock ford a/c box hanging on your fire wall, I went with the vintage air unit, & will be puting the condensor betwenn the radiator & cooler like you did,

Jay, how hard are you running it? Any mods? thanks!


I like to see the boost up around 20-23 when into the throttle. :D The pump was gone through by an old pro who wasn't a fan of too much fuel (excess smoke), so it's pretty tame as far as 12V hotrodders go. He tweeked something to get a little more RPM (not a new gov spring) and I have a K+N filter and Rip Rook's exhaust (4" from downpipe back). Pretty much stock.

Not a fan of excess black smoke!!! BLASPHEMY! :flipoff2:

Chris

a buddy has a 12v in a 91 crew chev 4x4 255/85/16 drw w/373 it had an auto/od and he was getting 13-16 swaped in a getrag 5spd/od and went up to 17-21.the 518 auto does not have a lockup converter and it slips alot not good for fuel economy

Thanks for the numbers Jay and High Clearance.
The truck had dealer installed ac when I got it, it sits on top of the heater box, and takes up most of the glove box. I spliced the hoses and am using the dodge condensor, compressor, and drier. The compressor is held on with 4 bolts, one of the bottom bolts was too close for comfort to the crossmember, so I used 3 bolts and ground the 4th tower off, so that it wouldn't crack the housing under a shock load. I thought about using a ford ac box (dealer ac was missing some pieces) but it would have put the turbo inside the ford box. My boss is planning a 12v swap into his ford motor home (van cab) and found that the med duty fords have an exhaust manifold that the turbo sits under. My other donor truck has a "fuel miser" torque converter in it according to the PO, once that truck is together I may look for another if I like it.