75 CJ6 Not Really A "Build"

Passenger side drop. It is all coming out of a 91 Blazer. Not going to use the axles from the chevy though.

 

I think that's a good choice........I'm using a LS376 crate motor here with the 4L70E 4 speed and an Atlas TC behind it.............Rear transmission mounts are no big deal you'll just have to make a cross member and use the factory rubber mount or aftermarket Urethane mount designed for the TC or Tranny or you can also frame mount the isolators on each side............although due to the weight it's probably best to mount it on the TC............I'm also exploring the notion of putting a rear .125" thick motor plate in between the engine and tranny , that way pulling the tranny for service becomes much easier....Also if you can find a 700r4 "K" 4-wheel drive case and swap your innards into as they are heavier duty than the standard case...

 

Soooooo, what's happening with the Dana 300 you mentioned back on page 2? That's a Texas pattern case correct?

 

Not sure yet given my track record of losing my track when building things. I want to see the sbc/700r4/NP241, hanging in the CJ6 frame before I finally believe that that's the direction this is going. I was toying with the idea of taking the T19 and D300 to the transmission shop to at least get an opinion on whether he thinks they need any work whether I keep them or not.

 

IIRC some of the Chevy NP241s are passenger drop. NP241C. Popular swap for a Wagoneer. How long is the 700R4/NP241 combo? A CJ-6 is longer than a CJ-5, but it's not a Wagoneer. Also, is there enough room between the rails to put the transmission in the center and the NP241 not interfere with the passenger side frame rail? And will you need to clock the NP241 up to fit? These are the typical problems putting a pickup truck drive train into a CJ... long, wide, hang down.

 

Your post is well timed Tim. We just yanked the engine/trans/t-case out this afternoon and it is now sitting on the floor of my increasingly crowded barn. To answer your questions/points to ponder, the length is about 42 inches from the front of the bell housing to the end of the slip yoke snout. I plan to run a slip yoke eliminator to get some of that length shortened. Very rough measurements (there was stuff stacked on my frame) show that the rear driveshaft will be over 20 inches long, maybe a few inches longer. I don't have much of a lift (probably 2") so hopefully the rear driveshaft will be okay. The transfer case on mine is passenger side drop. The crossmember it had been sitting on is four or more inches wider than my frame. I don't know yet if the transfer case will clear frame when the engine is centered. The NP 241 does look like it will hang down quite a bit if it isn't clocked upward. A sloppy measuring of the exhaust manifold flanges (outside to outside) currently on the 350 indicates that they will be too wide to fit between the frame rails. They are rear dumps. Some form of block hugger manifold looks like a necessity.
My immediate plan is to reassemble my bubba engineering wooden hoist so that I can pull the 304 again and then hang the other engine and running gear over the frame to see what will clear and what won't. Worst case is I stick with the 304 and manual setup I already have but I was getting to like the idea of a Jeep my three girls could drive. Not to mention overdrive and fuel injection.

 

Girls can (and arguable should learn to) drive stick shifts too But I agree that overdrive and fuel injection are handy features to have.

 

These are old girls. 20 and up and don't live at home anymore. While they can drive my four speed flat fender in four low, they would be scary driving in two high on pavement, especially hill starts and the like. I don't have the patience to teach them and I don't think they really want to learn. They may have to though, I am not much of a fabricator and some of the things Timgr pointed out may be problematic enough for me to change plans, again.

 

You could still use the SBC/700R4 with the Dana 20 from the original drive train. It would require a conversion kit, which is a significant expense, but it appears that the Novak kit is a spud shaft that does not require disassembly of the transmission. Adapting the Turbo Hydramatic 700R-4 & 4L60-E (early version) Transmissions to the Jeep Dana Models 18 & 20 Transfer Cases

 

How about a Dana 300? Wouldn't that bolt up in place of the 241?

 

Not without a conversion kit. Adapting the Turbo Hydramatic 700R-4 & Early 4L60-E Transmissions to the Jeep Dana Model 300 Transfer Case And he'd need to buy a D300. I thought the D300 he has is a Texas pattern case, which is quite valuable on its own, and not suitable for adapting to an automatic.

 

My bad, I thought the 241 had the same round bolt pattern and 23 spline input as the 300. I was thinking if the 700r4 already was adapted to the 241, it would swap over.

 

Hmm. I should not be so sure. The 241 is a NP transfer case, so you'd expect it to have a round NP adapter. I presume that the 241 has its own (round pattern) adapter and accepts a 27 spline shaft. Novak says you can use the 4WD 700R4 and their adapter if you replace the D300 input shaft with their 27 spline version. They also offer a replacement 23 spline transmission output shaft that fits the D300 without changes (requiring transmission disassembly for installation). So the 300 is a 23 spline input, and the 241 is 27 spline - something has to change there. Likely the NP241 adapter is clocked different than the Novak D300 adapter, but you may be able to redrill the NP241 adapter to get a different clocking

 

The Dana 20 that was in it is gone. I am not opposed to going with a 300 or a 20. If I sell my T19/Dana300 it should offset a lot if not all of the conversion kit cost. Had a full day today and didn't even get to look at the Jeep. I really do appreciate the discussion. Very helpful.

 

The 300 is the better choice, mostly due to its better low range ratio. However, 20s should be cheap on the used market. IMO you don't need as low a crawl ratio with an automatic as you would want with a manual transmission - it's a different two-footed driving style. Still, you may want better gearing than you'll get with the 700R4. With 3.73 axles and the D300, you'd be at a 30 crawl ratio ... With the overdrive transmission, a deeper axle ratio might make sense. Ultimately, you could nearly double your crawl ratio with 4.56 axles and TeraLow gears in a D300.

Also, I looked at the Tera gears for both the D20 and D300, and retail is about $300 more for the D20 (ca $1000 vs $700). So if you were thinking of going with a gear set, you'd likely more than make back the difference in initial purchase price between a 20 and a 300.

 

BTW this kinda seems like a "build" to me ...

 

Have made a little bit of progress. Rolled the tub outside to degrime it a little. I used Oven cleaner on the bottom and sprayed some sprayable Jasco stripper all over the rest. The Jasco took off very little paint. I was surprised at how tough the Forest Service green used by AMC is. The oven cleaner took off lots of grease and grime and rust but it didn't touch what was left of the undercoating.

Pulled the engine, transmission, and transfer case from the 91 Blazer and set it on the barn floor so that it could bleed out and make a mess of my floor. It also gave me something to trip over while I was reassembling my wooden gantry hoist since it was in the only area left in my barn big enough to work on it.

Lastly, I used the hoist to pull the 304 out of the frame. Was kind of sad doing it. It may still end up going back in the frame. I had planned to tape off on the frame where the front and rear surfaces of the block came to and the tip of the water pump, to give me a ballpark of where the new engine should sit. But in my haste I forgot. I guess I can just measure from the motor mount holes.

Next step is to rig up a way to hang the other running gear to try to see what the most obvious obstacles are going to be.

 

I am trying not to use the "B" word Tim. That means more money and time.

 

Didn't get as much time on the Jeep today as I hoped to but at least I got the new running gear hanging between the rails. I really wish I had taken more measurements of where the 304 sat in relation to everything else (oil pan to differential clearance, fan to radiator clearance, dead center or offset, etc.).


Didn't take too long to figure out that my Chevy V8 to CJ engine mount kit wasn't designed for this frame.


I think I actually might have the shorter mounts on another Chevy engine I have around here somewhere. If not, I will have to decided whether to modify these or order the narrow ones.
The rear driveshaft doesn't concern me as much as the front one at this point. I didn't get a chance to measure or mock up anything, but I think the rear will be okay with a slip yoke eliminator and maybe some shimming to get angles right.

The front shaft might be problematic. The front differential yoke appears to be more inboard than the yoke on the transfer case. Just eyeballing it looks like there may be very little room where the driveshaft will run under/next to the passenger side, front corner of the transmission oil pan. Seems like it will work, possibly with a smaller than usual driveshaft tube diameter, and, maybe a little bit of suspension lift. The suspension lift would also help get a little space under the NP241. It's stock clocking puts it down there pretty far. Of course if I do that I might need bigger tires so it doesn't look goofy with a lift and skinny tires. I wonder if that was what Timgr was talking about. Hmmm

 

You're seeing why V6 Commandos had a 2-pc front driveshaft - to get around the bulk of the th400.