Bad Thud in drivetrain, videos.......help

[lawdogg]

I'm amazed, that is a great solution. Thank you!

[DoctorDex]

Curious about a couple more things:

1. How did you cut the V into the VCU & planetary gear? Do you have any pics of how deep you went in?

2. Did you have any problems with the "balance" of the whole assembly? Do you get any additional vibration?

3. When you were welding the VCU, did you have any problems with "goo" coming out? Any problems with warping?

4. Interested to know did you pull you center dif (and reinstall it) with the transaxle still in the car?

[Phattlard]

I didn't realy "cut" a V into the planetary gear set and VCU, I used a grinder to chamfer the mating edges, just to make it a little deeper so its still a solid weld after i cleaned it up. Its like a dremel, but a beastly air tool version, idk what its called.


2. I didn't balance anything, Didin't actualyl even think of that, but no vibrations that I have experienced yet.......Havent gone any faster than 120 tho, not that I do it regularly anyway.

3. Yea welding obviously overheats the metal, so I could only weld a couple inches at a time, then ran the part under water to cool it down. No Goo coming out from the vcu during welding, but I beleive my VCU was shot prior to all this, by means of the "jack test".

4. No I pulled the whole tranny, then tore it apart to inspect everything and install new clutch, Its only my 3rd tranny rebuild so I wanted to be sure I did it right after spending 1200ish on synchros bearings and seals and a 2nd gear. But I think I saw a thread were someone swaped an output shaft while the tranny was still in the car, though the end cap on the passenger side wheel well. Never tryed it tho. You would have to take the input shaft seal off, then the input shaft retainer bolt, and that input shaft is a bitch to get out of the bearing even with the tranny out of my car, had to use a press.

[Phattlard]

forgot an important detail. you have to weld it a certain order to make sure everything is lined up perfect. If welding the output shaft to the planetary gears, you have to put the center diff assembly together as if it was when its in the tranny. Then jsut leave the end cap off (the cap of the diff housing with the 4 pins) AND then slide that little weird shaped gear with splines on the TC side of the diff housing to proerly align the output shaft. Its hard to explain without pictures. you can weld the output shaft, and you must grind that surface smooth because it makes contact to the end cap i beleive, It had oil grooves so maybe its liek a bearing surface type of deal. The you can take it apart, and weld the vcu to the planetary gears. clean it up and your ready to go. Use duck tape to cover the planetary gears so no slag gets caught, out it will chew the gears all up. Short version, If it not lined up perfectly somethin is going to wear improper and possibly fail.

[HTOWNSTEALTHTTMAN]

this is good info, thanks for all the pics. Its good to know all the issues our trannys have so we can trouble shoot

[DoctorDex]

I have a new VCU, output shaft and planetary and I still have a thud. My excess play comes from the oblong dowel pins holes.

I think I might try a similar idea, except I think what I'm going to do is:

1. Tap the Dowel pins almost all the way out of the planetary gear.

2. Then put the planetary (and dowel pins) in position over top of the VCU.

3. Weld the dowel pins to the VCU and then pull the planetary gear off the dowel pins. This would leave me with a VCU with dowel pins sticking out of the top.

4. Then I'm going to fill in the remainder of the dowel pin holes and grind it flat.

5. Then I'd reassemble the hole thing, ie. put the sun gear on and then press the planetary gear onto the dowel pins.

6. If I preload the the dowel pins & the VCU this should hold up during accel, but I'm a little worried it'll snap if I hammer it in reverse or if I down shift quickly. Therefore, I think I'll do what you did and I'll add a little insurance by cutting a V and welding around the outside of the planetary-VCU.

Edit: I changed my mind about using this method. I was to scared to try and attempt to weld the VCU as it is made from hardened steel. Hardened steel tends to crack when you try to weld it, so I didn't want to risk it.

[Phattlard]

That is a good idea, someone suggested a while back to just tap out the old dowel pins and make provisions for larger dowel pins, and drill larger holes into the vcu to almost "renew" the dowelpins/hole with a tighter clearance. I also thought about what your saying " snapping the car in reverse", but idk who ever launches the car in reverse, lol I think that is the only way to break this weld if anything, but I get what your saying by snapping inreverse, I don't think that will be a problem at all, as long as your weld is strong. Actually After everything is welded together you could have it balanced, the output shaft has balancing holes drilled into the ends of it. So after welding you could balance it as an asembly maybe a driveshaft shop??, but you would have to weld the output shaft as well so it stayed together. I really love these cars, I think it would be cool to be able to get a subaru center diff or some center diff readily availble that would be modified to fit this car so we don't have to wait for someone to sell theirs.......good luck with your tranny.

[DoctorDex]

Originally Posted by Phattlard

I really love these cars, I think it would be cool to be able to get a subaru center diff or some center diff readily availble that would be modified to fit this car so we don't have to wait for someone to sell theirs.......good luck with your tranny.

I'm hoping supercar will come out with their Quaife centre dif. soon and that should solve our problems. I've heard rumors that it should be ready in the new year. I just hope it fits the 18 spline output shaft...

[keithmac]

Good info here guys, I`ve got the horrible clunk as well and assume it`s the worn holes syndrome. I take it if you weld it all up you have to completely strip the gearbox to fit the output shaft back in i.e. you can`t do it with the `box still in the car?.

If you can`t oversizing the dowel pins seems a better be for me, can`t face taking the bloody gearbox out again!.

[Phattlard]

resizing the dowel pins or welding it, the tranny needs to come out, pretty sure. I admit its a bitch. But after doing it about 5 times on a 3000gt, it gets easy.