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I have a cj7 that I am going install an AMC 360 with Howell injection, mild cam, and a little head work. My question is how well will the Borg warner t5 held up? Bad idea? Or is swapping to a np435 or nv4500 mandatory?

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jrahman....Thanks for joining us at the forums! Interesting swap, straightforward with regard to using factory engine brackets (V-8 304 variety) and the common bellhousing mate-up with the AMC 232/258/4.0L inline sixes. AMC was smart here, much like Chevrolet and the small- and big-block V-8/inline six common bellhousing approach during the 194/230/250/292 inline six era.

The lighter duty T-5 is troublesome even behind a 4.2L six. The V-8 you describe should be putting out 280 or so horsepower, and that's a far cry from the 110-120 range of the 4.2L/258. There was a common swap to the BW World Class T5 (Ford H.O. Mustang variety) available from Advance Adapters when this transmission was also offered as a new replacement unit. WC T-5 units held up and offered overdrive like you currently enjoy.

Your NP435 and NV4500 options each work. With the NP435, you loose the overdrive, a highway deficit. The NV4500 swap, depicted in my Jeep CJ Rebuilder's Manual: 1972-86, works well and is a massive, bulletproof unit. Lots of iron and very rugged. Concerns with the NV4500 are availability and use of the right input shaft. See the Advance Adapters catalog online for details here: http://www.advanceadapters.com. In my CJ rebuilder's book, the NV4500 unit was new. Today, the options are "good used" or "rebuilt".

A route popular now is the Aisin AX15, new or used, in my view a high quality "light duty" transmission in league with the BW T-5 World Class. It's durable and well engineered, holds up to horsepower in the 300 range, and has close-tolerance gear fit for long life. Treated properly, these units can go 200-250,000 miles behind a 4.0L inline six. The downside is no compound low gear like the NP435 or NV4500. Think of the AX15 as a closer ratio, lighter-duty mid-size truck or sporty passenger car unit, a reasonable candidate for the Toyota Tacoma, a turbocharged Toyota Supra or a V-6 Dodge Dakota. The NV3500/3550 fits this league as well, most Jeep builders see the AX15 as better than the NV3550.

This really depends upon your planned use. If I were in it for the long haul and did a lot of off-roading with a highway need for overdrive and fuel efficiency, the rugged, clunky shifting NV4500 would still be my choice. If lower (numerically higher) axle gearing is in the works, the closer ratio 5-speed AX15 without compound low would be a consideration. I cleave toward the more rugged, higher torque rated transmissions like the 3/4-ton and 1-ton truck domestic applications.

The AX15, NV4500 or NP435 would each require adapters for your application. The Dana 300 needs a clocking ring in some swaps. Reviewing the Advance Adapters catalog can be helpful in breaking this down by needed parts and cost-wise.

Glad to continue the discussion and hear more about your CJ-7 project. There are several very well done Jeep CJs among the forum members here at the Jeep CJ forum section!

 

Moses

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I Believe have a AMC th400 that I could have built. Th400 are pretty strong and would only need an adaptor at my 300 case. Is the AMC version as strong as the gm version? Or is the case just different? Thanks for your response. I don't want to anything twice. Well thought plans seem to cost less..lol

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You're fortunate to find a good GM THM400 transmission with an AMC case, jrahman...The AMC THM400 version was somewhat popular in the '70s.  Very rugged and reliable.  Limited to three speeds forward, no overdrive.  If a three-speed is acceptable, this would be a good choice and fits the chassis.  The THM400 was not used with the Dana 300 as you note.  An adapter would be necessary.

 

You would have the convenience of an automatic if that's what you want.  We had a Grand Wagoneer with the 360 V-8 and a 727 Torqueflite (factory).  Great drivability like the THM400, it had tall axle gearing.  All depends upon your objectives.  A 5-speed manual truck transmission with compound low plus overdrive like the NV4500 is the opposite end of the spectrum from a 3-speed automatic.

 

Let's discuss intended uses for the Jeep and primary goals around performance...That would help with the transmission choice.

 

Moses

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Moses, my jeep will be on and off road. Thinking automatic due left hip pain. Not having to push the clutch pedal may be a good idea.I don't plans driving highway speeds and primarily will use it offroad.

Places like silver lake sand dunes and Bundy hill both in Michigan.i will be upgrading axles eventually. Correctly have an AMC 20 with one piece axles and 4:10 gears and front Dana 30 4:10 open carrier.

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jrahman...With the off-road use, the THM400 could play out nicely.  The 4.10 gears would also be fine with tires of 33"-35" diameter and the automatic.  The Dana 300, even with stock gearing, has a decent low range ratio...You'd have torque multiplication at low speeds for crawl ratio, the tires would work well.  On that note, what is your planned tire diameter?  We can do some quick math on the engine rpm at cruise highway speeds.

 

If the overdrive is not a deal breaker, this makes sense.  I really like the THM400, have run them in 1980s Suburban 3/4-ton 4x4s with enormous success.  These units were in Class A motorhomes and muscle cars with massive horsepower.  To answer your earlier question, the AMC version is simply a housing adaptation to facilitate mounting to the AMC engine block.  Internally, this is a rugged THM400.  Jeep had the good sense to use these units in the later Kaiser era and well into the AMC/Jeep period with engines to 401 cubic inches.

 

Moses

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Moses so I decided to go with the th400 trans. Ordered Novak adaptor and waiting for it to show up then off to rebuilders. Living near a GM hydramatic plants there's a lot great trans rebuilders. Thanks for your advice. Jim

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This should be a snappy package!  Keep us posted with details about the project...Will you need to cut and size the driveshafts?  Have a quick kickdown switch solution?  Painless Wiring makes some stuff here... 

 

Moses

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