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BluDestiny

T3 mustache bar in early 4/70 240z causing r180 diff to move back

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So I started to install my T3 goodies from the black Friday sale this past weekend. I have the mustache bar and drop mounts and rear control arms going in. 

 

I currently have an STI r180 diff with Beta motorsports stubs and stock 240z axles and a RT mount. 

 

The issue I'm having is that after fitting the T3 mustache bar, it pulls the diff back about half an inch and that is causing the front diff crossmember to not line up.  This is pictured below:

20190226_170924.thumb.jpg.567708cd3a9e083f0d95a94efe5c872d.jpg

 

I understand the early 240z had the diff slightly more forward and htis was fixed in the 72-73 cars. I am wondering if I need a different cross member or mount. Below is a picture of the early 70-71 mount and later 72-73 mount, which look almost identical (but I have not found any evidence that they are different), along with a picture of the crossmember and mount I have.

5980718edf8d6_S30Differential-FrontMountInsulators-OE-240Zearlyvslate-bottom.jpg.fc9a0a3482b8b17206ba0a086586fd9f.thumb.jpg.5c403df22f933758cc261583fd420aa3.jpg1714151575_R180earlymountandcrossmemeber.thumb.JPG.f9f49b8c67798982468d8e096df9bf93.JPG

 

I managed to get two bolts in the cross member, but I had to really loosen the bolts for the T3 mustache bar to the diff, I don't think it will all bolt down snug unless I can get the front dif mount to move back. 

20190226_183058.thumb.jpg.bc8fa36326ec606079c538ca8b0a51e1.jpg

 

Here is a picture of how all the parts are installed currently. I want the diff positioned towards the rear to correct the axles angled, but I don't know what I need to make the front of the diff line up properly.

 20190226_170932.thumb.jpg.0bfb29f167afeb28d8340ad888d25627.jpg

 

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So I just found this thread, and this might be the cure if anyone can confirm that they re positioned a 70-71 diff to the 72-73 position and only had to flip the diff bushing. Here is the thread, and the main picture from the thread. I will try that later this week and see if that solves the problem. I tried it quickly last night and the center line of the diff cross member didn't seem to line up, but it was getting dark. https://www.classiczcars.com/forums/topic/59052-71-z-differential-front-mount/

 

1977140701_difflineup.thumb.jpeg.a36109b0d092167cf5c1f0e3480e4e86.jpeg

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If I could be so bold as to offer a suggestion. 

 

I would take this chance to use an RT mount style setup up top and a snubber on the bottom. Less leverage against the brand new T3 bar. 

 

There is definitely some variance as the RT mounts commercially sold usually have 3 holes per side to deal with the offset to help line up the differential.

 

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On 2/27/2019 at 6:45 AM, BluDestiny said:

I understand the early 240z had the diff slightly more forward and htis was fixed in the 72-73 cars. I am wondering if I need a different cross member or mount. Below is a picture of the early 70-71 mount and later 72-73 mount, which look almost identical (but I have not found any evidence that they are different), along with a picture of the crossmember and mount I have.

 

Here is a picture of how all the parts are installed currently. I want the diff positioned towards the rear to correct the axles angled, but I don't know what I need to make the front of the diff line up properly.

 

Might be easier for you to just get the GM transmission mount and hang the diff from your Technoversion R/T mount.  Even with the snubber you can still get some thumping as the diff nose moves up and down.

 

But you might have a new problem, in that your propeller shaft is not as engaged as it was.  It's pulled out of the transmission by that /12 inch you mentioned.  Better check spline engagement.

 

image.thumb.png.8a9ad919e735cd941ada232d7766d3b2.png

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Yeah I think the driveshaft length will be an issue. I'll also have to move the RT mount rearward if there is space.

 

So I've also planned on going with a KA transmission down the line as I have 2 cores to rebuild and a lead on a lot of L series bell housings. But I know that will shorten the driveshaft even further. I don' t want to lengthen my driveshaft, then shorten it again later this summer. 

 

I've also read that that GM poly mount causes too much lift on the nose of the diff. Not going with that bushing as my current rubber bushing is doing fine. 

Edited by BluDestiny

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You can tell if the diff is right because the half-shafts will be perpendicular with the wheels.  You can shim the GM mount downward to get the right angle. 

 

With the KA transmission (71C) the short propeller shaft will be correct.  You moved the diff back, so the shaft needs to be lengthened, not shortened, to use the stock transmission.

 

So an RT mount with GM mount, shimmed downward, and the short propeller shaft with a 71C swap should get everything right.

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I meant lengthen first then shorten later, as you said. I'm probably going to start getting a bell housing machined so that I test fit a KA trans.

 

I have a track day 3rd weekend of April so I'm hoping to get as much of this done as I can before then, pending funds.

 

T3 has mounts that work with a KA trans along with a new front diff bracket. 

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1 hour ago, BluDestiny said:

 I'll also have to move the RT mount rearward if there is space.

 

The RT mount should already be right.  The early 240Z forward-mounted diff is "wrong".

 

I'll quit now...

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NewZed is correct, GM bushing up top and the pyramid snubber on bottom. 

 

Not sure with the parts in question. T3 mustache bar I recall had a misalignment issue some have encountered. Using a snubber on the diff mount and the RT mount to hand the differential would allow for some adjustment. I'll search for that T3 thread in question.

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So I got it all in, I did have to flip the diff mount (move the diff position backwards aka the later style) and I had cut the spacer down to 15/16ths and buy some new length bolts. 

Here are the spacer pics when I had the diff in the stock, forward 1970 position, notice the amount of "slack" in the spacer to diff cover vs when I rotated the lower diff mount 180* forward to move the diff back to the 1972 position:

1087808026_diffforward.thumb.jpg.2763923dd9a4fcea03641c60580897c4.jpg1113212354_diffrearward.thumb.jpg.dc32e70b9f543c61e625086ca712b250.jpg

 

And this is the final product. I need to get it aligned still, but I have work on the front also

20190312_184826.thumb.jpg.10822bd1c180efeac81c8dfac639d288.jpg

 

 

Here is are some bonus pics of the Trans mount (type 2) that I will be replacing with the T3 KA trans mount (when I get the trans rebuilt)

1685011029_transmounttypes.thumb.PNG.f50f5a2d284e9d69575d0ffc8a019bb5.PNG20190312_184855.thumb.jpg.ba4ae46b94434f2188c90a3f5cede1bf.jpg

 

And here is the amount the driveshaft pulls out. My driveshaft measures 21 1/8 inch from u joint center to center, so I'm looking for the longer 22 1/4 inch. I have a few leads, but need to pick it up.

20190312_184900.thumb.jpg.7ec375031d22894c8da2c07065f9e075.jpg

 

Final plans are to go with the Ka transmission with a converted L bellhousing, T3 KA trans mount, T3 front diff mount and the "power braces" they sell. The front is getting T3 arms and TC rods, and new tie rods. Eventually I'll get the steering rack rebuilt and put in new bushings and a solid steering knuckle. Then I think the suspension will be done. 

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Doing the fronts now. Small problem I ran into was the T3 front control arm ball joint bolts were longer than factory and therefor I couldn't just bolt the strut back onto the steering knuckle. I had to buy some bump steer spacers/roll center adjusters, which was no biggie since I probably needed them. Also could not get one tie rod off and the new outer tie rods I bought are both right hand threaded. My driver side inner tie rod was left hand threaded and crusty. So I got some new inner and outer tie rods. along with a solid steering rack bushing and poly steering rack mounts (still have to put those in). 

 

20190317_160822.thumb.jpg.22e76ad6d08eea21eaa7589a277d28fc.jpg

 

Also got the later and longer style driveshaft.

 

20190317_171201.thumb.jpg.700db0d2b2807e02264d24c70475e9b4.jpg20190317_171131.thumb.jpg.4a833723986a01fbe94c15ec7518dde3.jpg

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So in the pic I posted I had already put on the new inner and outer tie rods. I rounded the lock nut off the passenger side, and then the ball from the inner tie rod ball came out. So I just got new inners and outers. The inners come off just with a 14" adjustable wrench and the outers come with it. 

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Hmm, did you have different inner tie rod ends or were they the factory ones with the tape on them? Both ones I have seen have a strange like 3 flats style, so I wasn't sure how you would get a wrench onto it. The new inners look like what you have and seem like they would take a big adjustable wrench.

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