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GTX fix up, on a budget with some unique twists

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    #16
    Nice! given my a few ideas for my GTX.
    My Hiroshima Screamer

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      #17
      Originally posted by 323GTX-RSA View Post
      Nice! given my a few ideas for my GTX.
      If you search for a couple of my older threads from 2011 when I had my last gtx, they might give you more ideas.

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        #18
        Thanks will do. There are only 3 GTX's in the whole of South Africa so no parts at all, and we didn't get the BG series here at all either. So everything I do on it is a mod of something else.
        My Hiroshima Screamer

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          #19
          Well I had to take a week off. Between playing dodge ball (yes I playing in a competitive dodge ball league) and a couple evening courses for work there wasn't anytime left to spend on the car.

          This week work was slow so I had a chance to start wrapping things up. Not many pictures since it's mainly been assembly work. First up was getting the bumpers back on and all the trim pieces back together. I flushed the rad out and installed it.

          The car mostly back together. Ready for wheels and a ride height check.


          Front suspension all back together.


          Rear suspension all together with the BG trailing arm installed.


          Ride height check. She had about a 1.5" rake to her.


          I ended up cutting 1 coil out of the top portion of the men springs. This portion is compressed all the time so it was an even half inch drop. This still leaves the car with a bit of a rake but it looks pretty good. If I don't like it in the future I will cut another coil out.

          With the suspension all buttoned up I focused on some maintenance items. The cooling system was full of this jelly like substance so I flushed it out with water. Changed the thermostat. Ran a rad flush chemical threw it and flushed it again. While I was at it I changed the engine oil and flushed brake fluid. Then took the car down for an alignment. I didn't slot the front struts enough to get tthe camber I wanted but the rear worked out well. I managed to get the front set to 0 camber 0 toe. In the rear it was set to -1 with 0 toe.



          Rear control arm angles look good at ride height


          After the alignment shop it was off for emissions testing unfortunately the car developed a very bad hesitation on light throttle tip in. I turned around and took the car back to the shop. On what whim I decided to do a tune up. It's a good thing I did. The spark plug holes were filling up with oil from a leaking valve cover gasket.

          All 4 plug wires came apart when I tried removing them

          An interesting note. A miata valve cover gasket can be used if you can't find one for a b6t. The bolt holes are slightly different shape but it all goes in place and seals up.

          Unfortunately the hesitation wasn't solved. I had a feeling that was going to be the case. My last gtx had a similar hesitation I was never able to solve.

          The car ended up passing emissions testing even with the hesitation. Monday I plan to remove the new cat so I don't ruin it and just drive the car. I'll see what I can do to solve the hesitation as i drive the car.

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            #20
            Something interesting I never noticed with my previous gtx or my old 2wd bf with a b6t swap.

            The check valve for the brake booster is in vacuum line going from the intake manifold to the fire wall.

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              #21
              Yep...On the Capri's they put a one way valve on the booster that you can use in a pinch.

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                #22
                Yep, but if you decide to not use the metal pipe on the firewall, just grab some very stiff hose and just about any booster check valve. I think I'm using one from a Nissan.

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                  #23
                  Guess I forgot to update this thread.

                  My missfire/hesitation issue has been solved. It took a little bit for me to figure out but in the end it was a self inflicted wound. When I did the thermostat the bracket that bolts to the top bolt go shoved up into the wiring harness and piping. It was forgotten about. Well that bracket is important as it has one of the ECU grounds bolted to it.

                  With out the ECU ground the ecu was no out putting the right injector pulse width causing a very bad lean spot. This caused my hesitation/missfire issue. With the ground fixed the car has never run better. I have put almost 5000km on the car now since doing all the suspension work with out a problem.

                  I am pushing hard to get my autocross car done before march so this car is getting put on the back burner, but at some point down the road I plan to rip the interior out of the car to fix some of the horrible wiring thats going on and install a new power moon roof I bought.

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                    #24
                    Glad to hear you found the issue.
                    ---Has ClubProtege helped you in someway? show your support by Contributing--- Click Here---

                    1992- project FE3..... 313 WHP @ 9.3psi




                    I pet my dash when I get into the car..."good car"
                    he actually has a mazda tree, parts grow on it

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                      #25
                      Well I was going to add to this after I finished rebuilding the transmission and had it installed, but since work is dead and I need to keep my self occupied I guess I'll add this write up now.

                      So my GTX has a bad transmission in it. 3rd gear is really bad. It grinds on the up shift and down shift. Even when you are gentile with it. I have been nursing it along while I sourced out parts to rebuild a spare one I got with the car.

                      I have documented tearing down and rebuilding these mazda G series transmissions in a number of different threads so I wont go into full details. I did take pictures and planned on filling in some more gaps that I haven't covered in the past.

                      If you are interested here are the links to some of the other info I have posted.




                      pages 12 and 13 have some info as well.


                      Lets start with the transmission. Yep it looks like a BF all wheel drive unit, I believe its known as a G5MR-X.


                      Lets talk about removing the center diff lock actuator. Its a pretty easy process I have seen talked about, but never really documented. So first off there is this bolt. Its a lock pin for the rod that moves the fork for the diff lock. You need to remove it. While you are at it also remove the sensor. This sensor is a pain in the but with out a sensor socket. The sensor is used to indicate when the diff lock in engaged.


                      Now removed the 17mm rear plug on the actuator.


                      When you look down inside you'll see the rod and it just so happens to have a slot in it. You'll use a flat head screw driver to turn the rod 90 degree. This is what the rod looks like with the actuator removed. This picture shows it in the normal operating position.



                      This picture shows the rod turned 90 degree so that you can remove the actuator


                      Now you undo the 3 mounting bolts and the actuator will slide off. YA!

                      Tearing down the transmission is pretty straight forward its very similar to a 2wd G series. I didn't take to many pictures of that process. I think I have explained the 2wd stuff enough in the past.

                      With mine tore down I saw why the transmission was busted. Thats a lot of metal on the magnet.


                      The center diff blew up/seized up and chewed its self to pieces. When this happens you get a lot of loud clicking/clunking when turning sharply. It can be pretty violet and loud.


                      At this point I decided to continue tearing down the transmission and inspecting it. The results weren't very good. This transmission has been used/abused chewed up, spit out and chewed up again. At the end of the day I threw everything but the counter shaft in the garbage. Its a good thing I have an issue with hording parts.


                      I'll be back later, work just decided its my turn to pressure wash the floors.
                      Last edited by crazycanadian; 03-28-2015, 01:56 AM.

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                        #26
                        All right. Well I am back at this again.

                        So with the transmission torn down, I started comparing parts from some of the other transmissions I have. Input shafts from a B6T 2wd, Mx3 V6 and the GTX. Can you tell them apart? In reality there are minor differences but any one of these could be interchanged and swapped around with out and issues other then gear ratios. The Mx3 has a different 3/4 ratio. The B6T 2wd and GTX transmissions are the same.


                        Here is the counter shafts. The mx3 has a wider pinion gear, its easy to tell it apart. The B6T and GTX are only slightly different though. The B6T pinion gear has 19 teeth, where as the GTX has 20 teeth. This has to do with the different final drive ratios. The B6T transmission has a 3.86 final drive, where as the GTX is 4.1005. Its pretty important to know this since the counter shaft isn't interchangeable.


                        At this point I started tearing things down further. Some fun pictures showing you how. Both the counter shaft and input shaft come apart similar. The top bearing needs to be pulled off. There isn't a lot of room to get the bearing splitter under the bearing with out wreaking the outer cage and pulling on the rollers, so I tend to just cut the outer cage off first.


                        On the input shaft under the bearing you'll find a snap ring. This locks the 3/4 hub and slider in place. With the snap ring removed you can now pull the hub off. Try not to pull the outer slider off, the dogs tend fall off and go all over the place. When you do pull the hub off you need to mark it. Both the hub and slider have to be installed in exactly the same orientation other wise you'll have issues. Sometime the hub can be pretty stuck. If you need to you can use the bearing splitter on 3rd gear and use 3rd gear to pull the hub off.


                        Your input shaft will now look like these guys. The one with the input bearing still on it is from an Mx3 transmission. The other one is from the GTX.


                        On the counter shaft under the top bearing you'll have the driven gear for 4th. This is usually press fit on and takes a little bit to pull off. Down lower you'll have another C-clip that needs to be removed. Then its time to remove the driven gear for 3rd. If you are going to do things this way just take car not to chip the teeth. It can take some finesse to get it apart.


                        At this point you are down at 2nd gear. I'll just slide off along with the syncro. There is another c-clip holding the 1,2 hub and slider in place. Once that's removed you can pull off the hub. Just like the 3/4 hub it can take a little muscle. You can get the bearing splitter under 1st gear if you need to pull it off. Once again mark the hub and slider, it has to be installed back in the same orientation. With everything off the counter shaft it ends up looking like these guys. 1 of them is from the mx3 and the other is from the gtx. This is where you can really see the difference in the widths of the pinion gears.

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                          #27
                          All right now lets get a little more detailed. When going threw a transmission there are a number of things you need to look at. First up is the clearance between the gear and the syncro. I am showing how this is done with a feeler gauge while its apart, but this is easier to do while things are still together. When worn out the gap between the syncro and the gear will be pretty small. 2 things can cause this. The clutching teeth on the syncro ring can wear out, but also the cone on the gear its self will wear. So make sure to check your clearance with the new syncro as well.


                          Here is why everything from my GTX transmission ended up in the garbage. These teeth on the slider should be sharp and pointed. Sometimes minor burring can be cleaned up, but this toast.


                          The clutching teeth on this gear are chipped. Often times if someones been grinding gears, these teeth would be rounded off. Once again they should be sharp.


                          This is what a good slider is supposed to look like.


                          This is a good set of clutching teeth.


                          There are some other clearances you need to check while the input shaft and counter shaft are still together. You can end up with wear on the gear its self causing to much end play. This is is checked for each gear with a feeler gauge. Usually if you have a problem in this area its caused by abuse and a heavy foot or a lack of oil.

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                            #28
                            There are some other things to look at, but I didn't have any good examples to show what I would be talking about. So I'll just keep things moving along.

                            The bearing and syncro kit I picked up. Some part numbers if anyone is every looking for one.




                            OEM mazda seals in this kit. I was pretty happy to see that.


                            When ever possible its best to use OEM syncro rings. You can see the difference between the factory and aftermarket ones. OEM one is on the left. The difference in shape of the teeth will affect shift quality. Aftermarket ones also tend to break teeth of when abused.


                            New bearings. Top to bottom. Diff bearings, counter/input shaft top bearings, transfer gear support bearing, counter shaft pinion bearing, input bearing. All the bearings between a 2wd drive transmission and a 4wd drive transmission are interchangeable. Right up threw all the G series transmissions I have pull apart.


                            At this point I haven't taken many other pictures. A fun fact I haven't talked about yet is how I have set this transmission up. In going threw all my parts and playing with gear ratio/rpm/speed calculators I decided to swap out the factory GTX 3rd and 4th, for the closer ratio Mx3 3rd and 4th gear. I am not building this car to be a power house, I want a little better around town fun. I have noticed shifting to 3rd there is a bit of a flat spot in the power band. The factory gear ratios are a pretty far spread. The closer ratio 3rd and 4th should help fix this. It just so happens this is the same gear ratio set up as a BP G series transmission. 4.10 final drive, close ratio 3rd and 4th. Anyone with a boosted BP, would actually benefit from swapping to a longer ratio escort/B6T/GTX longer ratio 3rd and 4th.

                            In order to do the gear ratio swaps you need to tear down the counter shaft and input shaft. You need to swap both the drive and driven gears as a matched set to do the swap properly. I have yet to find a G series transmission that has a different 1st and 2nd ratio.

                            At this point I have the counter shaft and input shafts reassembled. I ended up using my mx3 input shaft because the reverse gear on it was in the best shape out of all the input shafts I have. The GTX counter shaft had to be used because of the pinion gear as mentioned earlier. So this was assembled using my old mx3 1st and 2nd driven gears due to them being in the best shape. I also used the driven mx3 3rd and 4th gears to complete the closer ratio swap. Fortunately for me I had a complete set of good OEM syncros. Now I am just waiting on time to clean up the case before I can move on to the next step.

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                              #29
                              Good info as usual, sir.

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                                #30
                                Great write up man, I wish I had time and lived near you. I'd take in all I could.
                                Cincinnati, ohio Bengals for life
                                "Who Dey"

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