Road manners 351/t18/3.73/33s
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Mountain Pass
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Road manners 351/t18/3.73/33s
I'm rebuilding a cj8 scrambler with basically an 80s f250 powertrain. I have a 97 351w being refreshed for a carb swap, a t18 that I'm rebuilding now, 3.73 axles in it and I think I'm going with either 235 or 255 85r16 tires. (31.8,33.3") at 65 mph in top gear the 235s would have me at 2570 rpms and the 255s about 2450. I won't be driving at 65 mph much. I average 46mph in my ranger in my normal driving for one tank so I'm not at 65mph much. I'll have a lower average speed in my scrambler. It will mostly be on road driving and someday I'd like to drive it to Alaska and back. Would this be an ok combo to use as a daily driver? I'm kinda limited on what transmissions I can use in my setup due to size. If it wasn't so big I can adapt a zf5 to my Dana 300 case but then I'd have to body lift and possibly modify the tunnel.
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Joined: Jan 2001
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From: Virginia
I think the zf would be worth it. I didn't know it was that much larger than a 4 speed though. It's about the same length isn't it? Could you use the floor pan cover from the Ford to help with clearance? The Ford trucks use a large bolt in pan, and I think the zf does have a higher raised area than the older 4 speed pans.
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Mountain Pass
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It's about 8" longer than the t18/bell housing/transfer case adapter. Which is quite a lot in a short wheelbase. Problem is that the actual tunnel in the floor itself might have to be modified. I refuse to go above a 1" body lift. 1" I could get used to but I hate the looks of body lifts.
Lead Driver
Joined: Feb 2013
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From: Roseville, MN
I had a CJ5 with a 258 six, close ratio T18, Dana 20, 4.27 gears and 235/85-16 tires. As a daily driver it wasn't too bad but it SUCKED on the highway. I could go 55 - 60 mph for short distances, like the amount of freeway I have on my way to work. And around town it was fine. But I drove it from Minnesota to Colorado, 'wheeled for a week and then drove back. Once. After that I flat towed it behind my pickup. 50 mph was about the fastest I could go for any length of time. The noise was just too fatiguing. Of course the fact that I got about 9 mpg towing it and about 10 driving it made the decision to tow a pretty easy one.
With 4.27 gears I was turning 2260 rpm at 50 mph. With 3.73 gears 2260 rpm is 57 mph. 3.73s and 33" tires bumps that up to 60 mph. It won't be a speed demon, but if you're willing to take your time it can work.
If you do want a 5 speed, the NV transmissions might be an option. I'm not sure how the NV4500 compares to a ZF5 in size, but people put them in CJs, so I'm thinking it's at least not as tall. And i have an NV3550 in my Bronco. It's not as strong as a 4500 or a ZF, but at least with my 302 I don't expect any trouble.
With 4.27 gears I was turning 2260 rpm at 50 mph. With 3.73 gears 2260 rpm is 57 mph. 3.73s and 33" tires bumps that up to 60 mph. It won't be a speed demon, but if you're willing to take your time it can work.
If you do want a 5 speed, the NV transmissions might be an option. I'm not sure how the NV4500 compares to a ZF5 in size, but people put them in CJs, so I'm thinking it's at least not as tall. And i have an NV3550 in my Bronco. It's not as strong as a 4500 or a ZF, but at least with my 302 I don't expect any trouble.
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Joined: Jul 2010
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From: Northeast, OK
I swapped a ZF5 in where an NP435 had been. The ZF is a much bigger tranny. It took the taller transmission cover to clear it, and getting it up and in was a challenge. But, the lowered RPM at 65 MPH with 3.50's and 30" tire's was well worth it. So, if you aren't driving much on the highway you'll be fine w/o it - especially given the length you mentioned. However, in my case the ZF was less than an inch longer than the 435, and I thought the NP was a bolt-in swap for a T18 or 19.
FTE Legend
Joined: Nov 2015
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From: Angier, NC
Could cut the floor/hump to Clear the top of the trany but the big thing is how long the new trany is as it is going into a SWB CJ8.
If it has any kind of lift kit and the short rear drive shafts is asking for trouble.
Dave - - - -
If it has any kind of lift kit and the short rear drive shafts is asking for trouble.
Dave - - - -
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Mountain Pass
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The length/angle shouldn't be an issue in a 8. Wouldn't be any shorter/steeper than a lifted cj5. Cutting is the problem. I would be willing to cut the tunnel cover as it's just thin aluminum plate. I can't cut the tub though. I searched 3 years to find an 8 with no rust that I could afford. I'm sure I could make it look nice but I'm keeping all my old parts in case I want to do a frame off resto eventually.
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Lead Driver
Joined: Feb 2013
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From: Roseville, MN
A CJ8 Scrambler has about a 20" longer wheelbase than a CJ5, so length definitely wouldn't be a problem.
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Mountain Pass
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Does anyone have a picture with detailed measurements of a zf5? Maybe with some height measurements from the center line of the input to the top of the case in a few spots. Also width along the top? My motor mounts I have move the engine a little to the drivers side and a little forward of the stock location for clearance reasons. I wonder if that would bring the case too close to the sides of the tunnel too.
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