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4.3 Build Advice

Discussion in 'Builds and Fabricators Forum' started by TIm E, Nov 5, 2018.

  1. Nov 7, 2018
    FinoCJ

    FinoCJ 1970 CJ5 Staff Member 2020 Sponsor

    Denver, CO
    Joined:
    Jul 18, 2013
    Messages:
    2,486
    Wow - I think that is why I don't like the sm465 - its going to hang down pretty low or you have to create some upward clearance in the floor pans? Any granny 4 speed has to have a large diameter granny gear - so its part of deal.
     
  2. Nov 7, 2018
    FinoCJ

    FinoCJ 1970 CJ5 Staff Member 2020 Sponsor

    Denver, CO
    Joined:
    Jul 18, 2013
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    2,486
    This pic of an installed sm465 shows how far up into the floor pan you can squeeze it to save some ground clearance, and also shows I think, how much the TC dropped down based on the twin sticks:
    [​IMG]
     
    TIm E likes this.
  3. Nov 7, 2018
    TIm E

    TIm E Member 2019 Sponsor

    NW Arkansas
    Joined:
    Mar 2, 2017
    Messages:
    630
    Definitely going to have to get creative to fit that big lump in there. No solid plans on the body yet, but have been considering flat-fender sheet metal on a CJ5 chassis (I have a nice 71 frame). I have accepted the fact that whatever body I go with, it will need some fab work. Guess I will cross that bridge when I come to it. Fully understand though, I'd be reluctant to cut into yours as well.

    Also a part of the reasoning on the 33" tires. I will do what I can to minimize how far stuff hangs down under there, but a little extra ground clearance from the tires will help.
     
  4. Nov 7, 2018
    jzeber

    jzeber Well-Known Member 2019 Sponsor

    Morgan Hill, Ca
    Joined:
    Nov 15, 2003
    Messages:
    2,419
    Yep the SM 465 is a big pig of a transmission.
     
  5. Nov 7, 2018
    shaun

    shaun Member

    ohio, Beavercreek
    Joined:
    Oct 15, 2015
    Messages:
    248
    Love to see those numbers...
     
  6. Nov 12, 2018
    Muzikp

    Muzikp Sponsor

    Sacramento Ca.
    Joined:
    Sep 27, 2016
    Messages:
    896
    I've managed to get my SM420 up inside pretty far so I didn't lose any ground clearance with it. You can jack up the cross member and raise the tranny as high as you like, or at least until you are limited by the engine angle with it up high. The 420 has a big hump that can(will) interfere with the front driveshaft but it can be remedied. Here's how much mine comes up through the floor, this is after I took some cross member spacers out to raise my cross member.

    Not sure how much the 4.3 changes the height of tranny but here's my SM420 on the oddfire.

    Here's how much the SM420 sticks up thru the floor
    [​IMG]

    [​IMG]

    Here's my cross member
    [​IMG]

    The granny low in the 420 is one of the best mods in the Jeep, I would probably do lockers first then the granny low. I'm also running 3:73 with 33" tires and I can cruise the freeway at 65 without cringing at the rpm I'm turning.
     
    ITLKSEZ likes this.
  7. Nov 12, 2018
    FinoCJ

    FinoCJ 1970 CJ5 Staff Member 2020 Sponsor

    Denver, CO
    Joined:
    Jul 18, 2013
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    If Tim doesn't mind me posting these up - here is what I have put together for a 4speed swaps. Obviously, different people do their swaps differently from using different bellhousing, or taping their own mounts in the bellhousing instead of adapters, making their own adapters etc, but I kind of stuck with the straightforward using the OEM bellhousing and adapters when convenient - mostly from Novak: Most of my general spec numbers come from Novak as well. These numbers do not include length of BOP bellhousing - as for any of these swaps the original OEM BOP bellhousing is used (and is approx 6.75" except for the 1971 once piece bellhousing - sorry you are on your own with that one). Additionally, since most will be keeping the D18, I did not include any info about that - this is really just a comparison of transmission and adapter lengths.

    1) Starting with a v6 225/T14 - this is kind of the starting point:
    OAL includes OEM 3" adapter between bellhousing and T14 ( 8 11/16"): 11.75"
    T14 is 80lbs
    CR for this set-up includes: 28.4 (3.73s); 37.2 (4.88s)....in my case with TLs and 4.88s I have 47.6
    cost: essentially free as its the stock set-up!

    2) SM420 swap: this does not need an adapter to OEM BOP bellhousing, but it may require bolting the bellhousing on to the sm420 before attaching to the engine. Does need an adapter to the D18 - but this does allow for using either a 6 or 10 spline input into the D18 (10 spline being the standard T14).
    OAL includes sm420 (10.4") and D18 adapter (4.4"): this adds up to 14.8" to me, but Novak says 15.2". So its about 3-3.5" longer than T14 set-up
    sm420 is 135lbs (lightest of the 4speeds)
    CR for this: 64.2 (3.73s); 84.0 (4.88s) ..... in my case with TLs and 4.88s it would be 107.6
    cost: $950: sm420/D18 adapter is $515 (Novak); sm420 rebuild kit $218 (Novak); used sm420 $200-250 (they are not the most common in my local area)

    3) SM465 swap: this does not need an adapter to OEM BOP bellhousing. Does need an adapter to the D18 - but this does allow for using either a 6 or 10 spline input into the D18 (10 spline being the standard T14).
    OAL includes sm465 (12") and D18 adapter (1"): this adds up to 13". So its only about 1.25" longer than T14 set-up
    sm465 is 175lbs (heaviest of the 4 speeds) - also has the tallest height at 18" (an inch more than the sm420 and 0.5" more than T18)
    CR for this: 60.1 (3.73s); 78.6 (4.88s) ..... in my case with TLs and 4.88s it would be 100.6
    cost: $850: sm465/D18 adapter is $518 (Novak); sm465 rebuild kit $229 (Novak); used sm465 $50-100 (they are very common in my area)

    4) T18 swap: There are a few more variations with T18s as there are some differences both with AMC and Ford versions, as well as some differences between the 4:1 and 6:1 AMC T18s and whether they are D18/D20 texas pattern or D300. An AMC T18 may use an adapter, whereas the ford 18 can be bolted directly to the T14 bellhousing with a bit of work. Most will need an adapter to the D18 - but this does allow for using either a 6 or 10 spline input into the D18 (10 spline being the standard T14).
    OAL includes T18 (12") and D18 adapter (1"): this adds up to 13". So its only about 1.25" longer than T14 set-up.
    T18 is 145lbs
    CR for this: 58.0 (3.73s); 75.8 (4.88s) ..... in my case with TLs and 4.88s it would be 97.1
    cost: $1000-1200; T18 to bellhousing adapter ($218 - but not required if you can drill and tap your own bellhousing); T18/D18 adapter is $518 (Novak); T18 rebuild kit $210 (Novak); used T18 $300-400 (these are least common and most expensive in my area)

    In short - all swaps require about $750 for a rebuild kit (assumed that is needed for any JY or CL transmission) and D18 adpater. For me at least, the T18 is the most desireable with gear ratios (and what I think is a better 2nd gear ratio of 3.09 than the SMs), may have the least issue with fit and size, but they have the most variations in the adaptions and are by far the most expensive and hard to find around here (at least in the correct short input configuration). I also like the sm420 for the small size, but it has its own oddities - especially the early versions without the sealed front retainer, rare to have back-up lights, and possible clearance issues with the bump, as well as a long D18 adapter. The sm465 is probably the cheapest way to go, but its a pretty big sucker. Probably can't go wrong with any of them...and all of them are going to cost close to $1000 just for the functioning pieces, and then there is still the clutch aspect, cross-member, driveshafts and floorpans.
     
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  8. Nov 12, 2018
    TIm E

    TIm E Member 2019 Sponsor

    NW Arkansas
    Joined:
    Mar 2, 2017
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    630
    Wow, just wind James up and watch him go! :clap:

    I don't mind one bit, great info and analysis sir.
     
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  9. Nov 12, 2018
    TIm E

    TIm E Member 2019 Sponsor

    NW Arkansas
    Joined:
    Mar 2, 2017
    Messages:
    630
    I am pretty much set on the SM465 since I have it; and have it disassembled, case cleaned, painted and ready for reassembly. Just waiting to pull the trigger on the D18 adapter pending a decision on the 6 or 10 spline mainshaft. 10 spline would allow me the option to transplant the OD from my 69 if needed.

    My SM465 came with the GM bellhousing and NP208/241 adapter for $70. A reproduction adapter goes for $250 at Novak, so I can probably sell that and at least break even on the purchase price. The seller did say it would sometimes pop out of third gear, common problem. It does have the later sleeve fix on the cluster, so I went ahead and ordered a new Torque Lock 3rd gear and shift collar/hub ($58 shipped on ebay). I also rebuilt the shift tower with all new springs and poppet balls. Gears, bearings and bushings all look great...like someone has been through it. Not sure I can reuse the bushings on the new adapter shaft as it is tough to get them off without damage. The whole rebuild kit may be a waste as everything looks really good...and did I mention it is beefy? I'll inspect it all closely and decide from there.

    Of particular interest from James' numbers is the length. The SBC bell may be slightly different in length than the BOP, but the 1.25" or so added length could be made up in moving the engine (4.3 in my case) forward a bit to keep t-case and driveshafts in their original location. I'll have to fab the motor mounts anyway. Radiator clearance will have to be checked among 100 other things, but figuring this stuff out is good therapy and keeps us sharp!
     
  10. Nov 13, 2018
    Jw60

    Jw60 Recovering Jeepaholic

    Sedalia MO.
    Joined:
    Oct 5, 2018
    Messages:
    392
    With a short water pump on the 4.3 i was able to keep the transmission at the same position for / aft and run a 65 mustang radiator. I threw the sm465 in there so the Transmission cover gasket is level with the floor. My air filter over the quadra jet on factory 4 barrel is within an inch of the hood.
    Radiator is as low as it can go and the flex fan is awfully close to the lower radiator hose and has made contact when flexing. I don't see much more room in front unless you get a cross flow radiator and hack the preshroud on the grill. The rear shaft doesn't look too bad 1.25" shorter.
     
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