Hmmm - new flex coupler (Guibo) won't fit

[tdskip]

So the old coupler on the 1968 came out in pieces, bolts were cooperative. So far so good. New replacement part looks like good quality.

But it won't fit, or more specifically the driveshaft won't let it fit.

The rear of the driveshaft has a sliding yoke but even with that fully depressed (in other words pressed all the way back in towards the rear of the car) I can't get the driveshaft to clear the coupler when the coupler is already on the back of the transmission.

The driveshaft yoke actually touches the rear of the transmission yoke so when I put the coupler on the transmission side yoke it won't allow the driveshaft to press up past the outer edge of the coupler.

I tried raising the transmission some but no difference in clearance. The rear of the car is on jackstands if that makes a difference.

Any ideas?

[tdskip]

Update - apparently this is normal and I have to drop the rear of the driveshaft?

[18Fiatsandcounting]

I've always got lots of ideas, and some might actually have some value now and then!

First, the rear of the car on jackstands isn't likely to be the problem. I'm having trouble picturing what you've got here, but I know this has come up before, and in fact GeoSpider on this forum had a similar problem back around October of last year.

Going by memory here, and starting from the rear of the transmission:
First you have a 3-pronged yoke that slides onto the output shaft of the transmission and is held in place with a large nut and a flat washer that you bend up on one side (against one side of the nut) to prevent it from rotating.
Next you have the giubo, and 3 of its holes are attached to the above yoke.
Next you have another 3-pronged yoke (for the other 3 holes on the giubo) that has a splined hollow shaft in the center, and a thin metal cover towards the rear of the car, and this metal cover can spin and should have a rubber seal on the rear.
The splined end of the forward driveshaft section (the one about 18 inches long) should fit through this rubber seal (if there is one) and then engage the splined center of that rear yoke. Sometimes you have to tilt the front driveshaft around and rotate it, in order to get it to slide into those splines. Removing the two nuts that hold the center driveshaft support in place sometimes helps with this.
There is one other aspect, and that is an "alignment washer" in the rear yoke that the very tip (the unsplined part) of the front driveshaft must fit into. It looks like: https://www.midwest-bayless.com/FIAT-12 ... e-nos.aspx My guess is that maybe this is where your driveshaft is getting hung up on?

If this sounds right, we can proceed from there.

-Bryan

[tdskip]

Hi there - hope you are doing well.

OK - once more, with feeling, and hopefully better explanations on my side.

My issue is that there is not enough clearance for the driveshaft end closest to the front of the car to clear the new rubber flex disk, it hits the rubber when I try to swing it up into place (it is disconnected at the front because I removed the old rubber flex disk).

I dropped the rear mount where the center bearing is located to try and give myself more room and that did not work.

My forward driveshaft connection is moving freely, that is I can pull it forward and back smoothly. Even when all the way back I do not have enough clearance.

The workshop manual that I have, which is not an original Fiat one, doesn't list this procedure as separate activity but it appears that I need to keep going and disconnect the four bolts where the torque tube attaches to the differential and then pull the entire driveshaft out.

Is that more clear?

[geospider]

Geospider here, as Bryan mentioned.
Yes, I redid mine last October. disconnect from the dif. Mark the flanges first so they go back in the same orientation.
then you have plenty of room to slide it in (stop laughing some of you)
Now, mine ('79, can't speak fro all years) has a plastic piece first with splines, then what I found out is this rotates separately from the metal splines in the input. so, once through the first part, spin shaft to line them up and slide again. Yes, we are still sliding. then attach the center piece, the lastly the rear yoke to the dif (lined up by reference marks made)
Once I learned this (yes, 2 hours prior to a car show and first meeting with Bryan), all went easily.

Geo

[18Fiatsandcounting]

I can attest to all that GeoSpider mentions, even the fact that he stayed up until the wee hours of the night to be able to drive his Fiat to the Fiat gathering in October. I was so totally impressed.

OK, back to tdskip. I keep forgetting that your '68 has a torque tube arrangement rather than a "simple" driveshaft. So, my suggestion, similar to GeoSpider's, is to disconnect the bolts that connect the driveshaft to the input of the differential and see what that buys you. It may be necessary on '68 models, if not on the later ones. When in doubt, follow what Geo has outlined.

-Bryan

[tdskip]

Thanks gentlemen, maybe I need to pretend there is an impending car show to help me crank it out!

Nice going Geo. Once we can be a bit more footloose I'll meet you guys in Carmel...

When I pulled the four bolts that connect the torque tube to the differential I'm sure I'll be able to slide the shaft forward and out, curious how I'll get the rear splines back one once I have the coupler installed.

I suppose it is time to just dive in, worst case is I'll get it towed to Mark Allison if I really muck it up.

Here is hope the coupler lasts a long time....

Thanks!

[18Fiatsandcounting]

You'll figure it out, and yes, the new giubo should last a long time. I've replaced mine every 20 or 30 years, but more because it just seemed like it should be replaced at that age, rather than there was actually something wrong with it.

However, they can and do fall apart, as you and SteinOnkel can attest to.

-Bryan

[tdskip]

Well, this is kind of of what I was expecting, and it isn't awesome.

I pulled the four bolts off that mate the torque tube to differential, that allowed me to slide the driveshaft forward and then down. That exposed the male splines on the differential input shaft that the torque tube slides on to

With the driveshaft forward and down I was able to install the flex coupler.

With the flex coupler installed the torque tube is fouling the male splines of the differential input shaft.

It appears all I have done is trade one problem for another.

EDIT - the front part of the driveshaft yoke that attaches to the flex disk slides in/out. It had been fully seated towards the rear of the car, it now is stuck without the ability to be further compressed about 1/2 inch from being fully seated. Even if it could be fully seated it wouldn't allow enough from to clear the differential input shaft, but this makes me wonder if the flex disk was installed wrong if it is defective and not allowing the driveshaft to move freely through it's center.

EDIT #2 - I'm pretty sure I am going to have to loosen the rear axle locating radius arms to allow for enough clearance....

[tdskip]

Spent more time staring at it and got some coaching on another forum and I am going to leave the rear axle alone and bolt the torque tube back up.

I think my issue is failing engine and transmission mounts, especially since the car is on my sloped driveway.

[18Fiatsandcounting]

Loose or sloppy mounts might explain it, and I only wish I knew more about the torque tube arrangement of the '68 spiders. Give it a try, and let us know what you find out.

-Bryan

[tdskip]

Will do Bryan.

Heading to Mark Allison’s for u-joints and new center support and then will give it another go. I’m probably going to get some engine mounts as well.

Will the rear of the car even higher in the air to get gravity helping me.

I’ll get it figured out - just a bit low earlier today.

[18Fiatsandcounting]

Hang in there skip, there's lots more Simpsons quotes awaiting you when you're done!

-Bryan

[tdskip]

I woke up convinced the engine and transmission mounts need to be refreshed - as I mentioned without the flex coupler in place the metal yokes make contact and that is going to destroy the flex coupler again.

[18Fiatsandcounting]

You beat me to it! Excellent, I'll bide my time, Smithers...

But seriously, I'm still having problems picturing what you've got here. Have you tried loosening the driveshaft center support bracket so that it hangs down, attaching the giubo to the 3-pronged yoke on the end of the driveshaft, and then raising this back up to attach to the other 3-pronged yoke on the rear of the transmission?

But maybe with a '68 and the torque tube arrangement, there's something very different than what I've seen on my later model years, and so I'm just spouting nonsense?

-Bryan