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S14 KA24DET: Trannies Suck When They Blow

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  • S14 KA24DET: Trannies Suck When They Blow

    Had a regional event this weekend and put a couple extra friends in SSM with the car for more feedback (new rear springs, new rear sway setting). Turned boost down a few psi just to be safe, and blew a transmission after 15 runs. Blowing trannies sucks.

    Take that however you want.

    There's a couple things I'm looking into now:
    1. The Avid motor mounts have poly inserts in them, but the transmission mount is a solid block. I'm wondering if we're tweaking the tranny when cornering and loading it up. I can't imagine it'd be good for gear or bearing tolerances in the transmission. Does anyone else run a solid transmission mount with semi-rigid motor mounts?

    2. The z32 transmission looks like the next upgrade for a KA24DET. I'm looking at the Mazworks or Xcessive kit. They cost about the same, but I'm sketchy on the Xcessive kit spacing the flywheel out. It'd be easier to install the Xcessive kit (no need to send a bellhousing in), and I'd be able to swap trannies without having to take the bellhousing apart. I'm hoping I won't have to worry about the transmission once I upgrade it, though, so I'm still leaning towards the slightly cleaner Mazworks kit. Thoughts or suggestions would be very welcome on this.

    3. Does anyone make straight cut gears or a dog engagement setup that drops into the 240? Was thinking of talking to DentSport about their transmission setup (a quick 1-2 would be killer for ProSolo). If I'm upgrading, I might as well go all the way.

    4. Should I start upgrading my stock half-shafts next? I was looking at the z32 TT and Q45 setup, which seems overkill. I've never seen a halfshaft on a 240sx let go, other than the drag racing guys.

    Once again, comments or suggestions would be very welcome. I want to make more power next year, but I also don't want to be afraid of anything breaking on the car. Seems like finishing off the drivetrain upgrades would be helpful.

  • #2
    1. I would use a tranny mount with same flexibility as your engine mount. don't know if that caused anything, but that has been known to destroy rear suspension on early Zs. The R180 diff is solid mounted to the moustache bar in the rear and then the moustache bar has rubber mounts ot the chassis. The diff has has rubber/poly bushings up front just like our R200. nonetheless, people tend to remove one set of bushings and not the other, then the solid mounted end winds up fatiguing and tearing apart the metal holding it in place. then they have to repair/replace the entire subframe instead of just install the proper bushings.

    so either go full solid or full poly or full rubber, but don't mix them

    meeting in a sec, but more later....
    Originally posted by SoSideways
    I don't care what color they are as long as they are LONG AND HARD.
    '04 G35 Sedan 6MT- The DD
    '96 240SX- The Track Toy


    • #3
      The q45 diff and axle/ tt axle setup is supposed to be 800whp proof.

      But the rear end ratio changes - that may help or hurt, depending on the power you're making - and the speeds you see in the events/ courses you run.
      1990 240sx - Aristo 2JZGTE, R154, GT37, Defsport Wilwood kit, KTS coilovers - daily driver
      1991 civic si - B18C5 / toda / ATS / hytech - autox
      2001 integra type R - Greddy td05-18g - garage queen


      • #4
        Don't have any comments on the Mazworx or other guys conversion kit- I was going to go for the Mazworx myself (never heard of the Xcessive kit), but have decided I'm just going to go to a full dog rig box. it's twice the price, but worth several seconds a lap- and based on the recent nats results and gauging the local fast guys against them, I need to speed up about 12 sec a lap! FAWK! I have a lot of work to do!

        OS giken makes a close ratio gearset for both S14-SR and Z32 trannies..
        SPL Parts designs and builds top shelf suspension components for street and track cars including Nissan, Infiniti, Scion, Subaru, Porsche and more.

        There are a couple companies out there that make dog ring and straight cut gears for the B13/B14 and Maxima trannies, but I'm not sure if they make anything that will work for the RWD chassis. I think it was PAL or PAR out of Australia. and it's NOT cheap. i.e. for those prices, you might as well go to a full G Force dog ring box.
        Originally posted by SoSideways
        I don't care what color they are as long as they are LONG AND HARD.
        '04 G35 Sedan 6MT- The DD
        '96 240SX- The Track Toy


        • #5
          Seems like something must be involved here besides the normal. Your mount idea might be something. I know I'm not too your power but SR trannies seem to hold up better. I realize there are only slight differences but it is basically a drop in. Might be worth a try. I thought about the Z32 one as well but have had no reason to go farther at this time.

          Does it always blow when the same person is behind the wheel and is it possible he could maybe do something a bit different?


          • #6
            Both trannies have gone with 2 different drivers, so it's not the driver.

            I thought about the G-Force T5 dog box, but that'd require new clutch plates, a new driveshaft, and I'd still need a bellhousing made. I looked at the Quaife and PPG gearsets, but I don't think they're worth the cost at the moment. PPG also notes on their site that they recommend the z32 tranny for more than 400 hp, which I'm assuming is at the crank. I'm easily beyond that now, and looking to go for more. I think it makes sense to go with the z32 tranny, and I can always upgrade it to a dog box later on.

            As for SR vs KA, I think the SR just doesn't make as much torque as the KA, so it isn't as abusive on the engine. Add the bigger wheels/ tires that I'm running, and it appears to just be too much for the smaller tranny. I've been reading the KA and SR trannies are identical, so I don't think the SR tranny would be an upgrade.

            Unfortunately the z32 tranny is said to be 19 lbs heavier, but at this point a heavy tranny is better than a dead one.


            • #7
              The SR/KA/CA and RB20 trans are all pretty much the same. The lower displacement motors that make torque, or spool hard hitting turbos later/softer will make the trans last longer.

              Torque and hard hitting turbos and wheel hop break the stock trans pretty fast. Unfortunately for you the KA has the most torque.

              I'm willing to bet SR trannys last longer due to slightly less torque and the fact a lot/some of them are newer and have less miles.

              You also might want to look into the Z33 6 speed. VERY strong and very cheap but needs an adapter plate for sure. I wouldn't space the flywheel either, seems like a bad idea.



              • #8
                What part failed inside the transmission? Was it the same part both times? Is there any signs of fatigue on failed part, or was it case of a suddon overload? (Hard launch?)

                I konw of an s13 with 335's all around that was breaking the output shaft on the launch. They thought it had something to do with the solid disc clutch not absorbing the shock of there 300+whp SR.


                • #9
                  The only difference between KA and SR transmissions are a couple of slightly different ratios.

                  I think 240sxTT is running a mustang transmission if you want to check with him.

                  I've seen a miata with a 3-rotor cosmo motor and a 2-speed powerglide that's won a national championship in a mod class and he didn't seem to miss his clutch! I think most of the cars that run in CP run autos with manual valve bodies, if you want to study that.

                  Maybe you just need to figure out how to fit a 4-5k stall torque converter to your manual tranny. That would put you fat in the power everytime you step on the gas and buffer the shock to the drivetrain...., ;-)
                  Don Johnson (really!)
                  Just so you know.


                  • #10
                    remember PJ's running something like 315mm R-comp. KA-T torque, stiff clutch, fat race tires, and lots of 1-2 power shifts should break things fast.


                    • #11
                      Originally posted by Jason M View Post
                      What part failed inside the transmission? Was it the same part both times? Is there any signs of fatigue on failed part, or was it case of a suddon overload? (Hard launch?)
                      Both times it failed on course while rolling onto the throttle, but haven't been able to inspect this tranny yet as it just happened yesterday. I'm really wondering about the mechanical stress on the transmission body, though, as both transmissions look to have failed while the car was laterally loaded. Hopefully I'll have it opened up and see what exactly failed on it later this week.


                      • #12
                        I've talked at length to JRS about the tranny failures in his S13 race car, and his belief is the combination of low rotating mass (auto flexplate, 5.5" clutch, etc), sticky tires, and constant on/off throttle wind up snapping gears.

                        Almost all of his failures were with the baulk rings. He's lose a gear in a race and open the case afterwards and the baulk ring would be laying in the bottom of the case in 3 pieces.

                        He said he was averaging about two races per transmission, so he would have one or two spares in his trailer for every race weekend. yeesh.

                        he went to the G force box and it's much better. he's ripped the teeth off the dog rings a couple times, but said that was due to his own driving errors and not the transmission.

                        In your case, you're in 1st and 2nd gear with huge tires and tons of traction with LOTS of hard on/off throttle transitions. lots of torque trying to twist around inside that transmission.

                        If you want something reliable, you're going to need to go to a Z32 tranny at least. the dog ring box may be too $$ for you, but would also be faster. you could choose your gear ratios and maybe set it up to run 1,2,3 on course instead of just 1 and 2. with as much torque as you've got with the KA-T, I'm not sure you need the gearing though- I would suspect you can spin the tires all the way through 2nd if you want, no?
                        Originally posted by SoSideways
                        I don't care what color they are as long as they are LONG AND HARD.
                        '04 G35 Sedan 6MT- The DD
                        '96 240SX- The Track Toy


                        • #13
                          While I don't have first hand experience, I know Jim(shoes 59) had said to me how he really didn't like the z32 positioning in the car, and found shifting quickly ackward
                          'Slicks on a car show me you care - broken axles show me you're trying'
                          [I]Nitrous Rental Cars - Turbo Festivas - Vehicular Lunacy[/I]


                          • #14
                            just my .02 i recently meet Rich from xcessive, seems like a decent knowledgeable guy. doesn't seem to care much about marketing. I don't know much about SCCA or Sponsers but with your name and reputation is a sponser like xcessive worth picking up the phone and see what you can do. I just see an opportunity, small time shop, big time SCCA racer!!!

                            there are a few people on here very local to him....

                            Most PM answers: F 17X9 +22, R 17X9 +35


                            • #15
                              The other Rich suggested I talk to him as well, but that was a while ago. I guess it couldn't hurt to ask, though. I definitely wouldn't call myself a "big time" racer, though :P

                              For the tranny, I'm pretty set on running the z32, mostly due to cost. I can always upgrade it later with a PPG gearset. I haven't looked into the T5 as much since the gear ratios would necessitate a new final drive (unless I can get custom gears, I suppose), clutch plates, and drive shaft. The z32 tranny will keep my 2nd gear capable of over 70mph without over-revving the engine (7200rpm) in stock form and it should provide the strength I need. I thought about doing a 1-2-3 setup with 2 and 3 inline for easier shifts, but the KA powerband is just too big to justify that. I only go into 3rd on ridiculously fast courses (80mph through cones can get "ridiculous").

                              The big thing is the less time and money I spend on the tranny, the more I can concentrate on redoing the aero and suspension, which will net more performance.

                              While I don't have first hand experience, I know Jim(shoes 59) had said to me how he really didn't like the z32 positioning in the car, and found shifting quickly ackward
                              Was that with a short shifter? Any idea which kit he used?