TH400 in a Land Rover Defender

Discussion in 'The "Juice Box"' started by Rossco, Jan 29, 2020.

  1. Rossco

    Rossco Greetings Earth Creatures

    Those of you that have followed my 455 build thread will be aware of my desire to have a Land Rover Defender powered by a mildly built 455. The 455 is now built and so my thoughts are turning towards the TH400.

    I should state that right from the beginning it has been my intent to keep the Defender fully functional in terms of its 4x4 capability. I know of at least 2 Defenders with LS engines in them but both of those are now rear wheel drive only......what's the point in that you may ask.

    So some time ago I turned my thoughts to how I could mate a TH400 to a Land Rover transfer case, either the older (and possibly stronger) LT230 or the later Borg Warner.

    It turned out to be far more simple than I first thought. All you need are a large milling machine, an equally large lathe, a 7" diameter alloy billet, a piece of 30mm thick alloy plate, and numerous off the shelf items.

    The adaptor is in two parts, a circular part which mates up to the TH400 in place of the tail extension. This is indexed into the TH400 which enables correct alignment of the transfer case.

    The second part is a plate which has countersunk holes to allow bolting through the circular part and picks up the tail extension bolt holes in the TH400. The plate will also carry the transmission mounts and pick up the existing mounts on the chassis.

    [​IMG]

    The TH400 needs to be fitted with the 9 1/4" 4x4 output shaft. I dont need a speedo gear as the speedo feed is on the transfer case.

    If I use the later Borg Warner I dont need to worry about oil contamination as they both use ATF. If I use the LT230 then I'll need to fit an additional oil seal in the second step shown above to stop any possibility of ATF and EP80/90 mixing.

    I'm also using a cut down drive flange which if I remember correctly came from a Rolls Royce. Those TH400's certainly got around.

    [​IMG]

    This will bolt up to a modified transfer case input shaft. I'll be machining a flange which will be press fitted onto the transfer case input shaft and fully welded. It'll fit roughly where the lower of the two lines is.

    [​IMG]

    Before anyone asks, I'm confident that this will carry the torque as I know a guy with a similar flanged setup behind a twin turbo 383 and the flange is about the only part he's not broken. I'll still be using 3/8" high shear strength cap screws though. They're rated at over 12,000lbs in shear.
     
    Last edited: Jan 29, 2020
    Tomahawk likes this.
  2. Rossco

    Rossco Greetings Earth Creatures

    Turned the flange and pressed it onto the transfer case input shaft, took 5 tonnes (11023lbs). I then welded it as well.

    [​IMG]

    [​IMG]

    [​IMG]

    [​IMG]
     
  3. Brandon Cocola

    Brandon Cocola Well-Known Member

    Could have switched to a divorced transfer case.

    If you were in the US transfer cases that bolt up to a th350 or 400 are all over the place.
     
    Rossco likes this.
  4. Rossco

    Rossco Greetings Earth Creatures

    @Brandon Cocola That's something I did consider. The beauty of doing it this way is that the setup is the same overall length as the original setup. So everything else remains the same.
     
  5. Rossco

    Rossco Greetings Earth Creatures

    Any thoughts on which to use?

    My instinct is the one on the left

    [​IMG]
     
  6. Matt69olds

    Matt69olds Well-Known Member

    Is that pictures of the sun shaft? If so, the sun gear inside the front planet will determine which tube to use. If it internal splines app around the suns shaft with the missing spline won’t fit.
     
  7. Rossco

    Rossco Greetings Earth Creatures

    @Matt69olds thanks for the info.

    Here's another question.

    I'm currently cleaning up and inspecting all the internals of the trans. The rebuild kit I have is a Jakes Performance kit which includes a Sonnax Line Pressure Booster Kit. Somewhere I remember reading that the Sonnax kit should not be used with a 65 to 67 trans. My switch pitch is an October 1967 originally fitted to a LeSabre. Am I correct in my recollection or is old age misting my mind?
     
    Last edited: Feb 4, 2020
  8. Matt69olds

    Matt69olds Well-Known Member

    There are compatibility issues between regulator valves with the built in orifice (first design) and the later pump housings (identified by a squared off casting on the regulator bore, near the snap ring groove) but I don’t remember the specifics. I have the article stapled to my garage wall at home.
     
    Rossco likes this.
  9. BRUCE ROE

    BRUCE ROE Well-Known Member

    The 67 Buick TH400 has a BOP engine mount, earlier did not.
    Cad did not till 68. Olds was BOP but only the 67 442 was the
    only switch pitch that had a speedometer output.

    As for output, I do not see a problem from 65 up. I do not deal
    with the 64 odd ball. Bruce Roe
     
  10. Rossco

    Rossco Greetings Earth Creatures

    Thanks Bruce, apologies but I'm not sure how that relates to my question regarding the Sonnax Line Pressure Boost Kit?
     
  11. Rossco

    Rossco Greetings Earth Creatures

    I cant find where I read about the Sonnax kit so I'm going to use it.

    I spent a couple of hours this morning cleaning and inspecting and noted that although all the pistons have been replaced with the alloy type there are only 3 springs on the intermediate clutch, and 8 each on the other two. Would I be right in thinking that I should purchase new springs and go for 8 on the intermediate and 16 on each of the others?
     
  12. BRUCE ROE

    BRUCE ROE Well-Known Member

    I do not know what the Sonnax is, but switch pitch and later internals
    are essentially identical. The differences are in the pump assembly,
    and an extra SWP oil passage that is otherwise ignored. Bruce
     
  13. Matt69olds

    Matt69olds Well-Known Member

    The factory setup for the intermediate clutch had 3 springs only. However, for some reason GM used a return spring with springs in each hole for the 4L80. The 400 is a progressive transmission, meaning each gear just adds another clutch, without releasing any other clutch pack. That means you don’t have to worry about clutch overlap like some other transmission designs.

    in other words, you can use the factory 3 return springs, or 12, or whatever.
     
  14. Matt69olds

    Matt69olds Well-Known Member

    There should be 16 springs in the forward clutch, and the factory direct clutch had 14 springs. There is an advantage to using 16 springs in the direct drum to prevent centrifugal apply of the clutch. The tiny amount of oil trapped in the drum during release can create enough pressure at high RPM to just barely apply the clutch, causing the frictions to glaze. Either install 16 springs, or measure in .410 from the outer diameter of the direct drum and drill a 1/16 hole. If you measure and drill accurately this will place the hole just inside of the outer piston sealing area.

    There is no disadvantage to drilling the bleed hole and using 16 springs. Other than possibly a harder engagement shifting into drive, the forward clutch will work fine with fewer springs.
     
  15. Rossco

    Rossco Greetings Earth Creatures

    @Matt69olds thanks, that makes things much clearer. I'm happy to drill the hole as described. Easy enough to set the direct drum up on the mill with the DRO. Before I do that the piston I have is the alloy type (#8625501) which has a small check valve in it. Does that remove the need to drill the drum?

    Additionally, I did the converter feed mod today. A 5/16" brass set screw is not the easiest thing to find in the UK so as I have a load of 8mm brass rod I threaded the converter feed hole M8 and made an M8 set screw. I've drilled it at 0.130"
     
    Last edited: Feb 7, 2020
  16. Rossco

    Rossco Greetings Earth Creatures

    Finally finished the trans to transfer case adapter today.

    [​IMG]

    [​IMG]
     
  17. Rossco

    Rossco Greetings Earth Creatures

    Test fitted the adapter setup to the transfer case.

    With a bushing in the transfer case and one in the adapter it was always a risk that if the bushings were out of alignment then the shaft wouldn't rotate. Even 0.003" misalignment would be enough to lock the shaft. Fortunately it looks like my machining has been spot on and the shaft turns easily.

    I was going to rebuild the transfer box but it turns out the viscous coupling is working so I'll clean the outside up and use it as is. If it fails then I'll rebuild it.

    The propshaft is from a Range Rover LSE and is the solid type, it clears the transmission by 3/8".

    Overall length comes in at 690mm (27 3/16") which is comparable with the standard setup. I can accomodate the 1/2" extra length by moving the engine forward.

    [​IMG]

    [​IMG]

    [​IMG]

    [​IMG]

    [​IMG]
     
  18. BRUCE ROE

    BRUCE ROE Well-Known Member

    Nice Work. Bruce Roe
     
    Rossco likes this.

Share This Page