oscs

iTrader: (19)

Anyone see a problem with the amount of engagement here? The mark closest to the u joint down to the input end marks how much is engaged on the output shaft of the trans. That leaves a little less than half of the slip yoke "non engaged" the car has solid motor mounts and a rubber trans mount.

I can always extend the driveshaft but this is what I got after trans swap.

Taxman20

iTrader: (11)

I normally shoot for about 3/4 inch from being fully in with the car on the ground. Did you check it in the air and the rear hanging? If so put a jack under the rear and get weight on the springs.

oscs

iTrader: (19)

Car was in the air with rear suspension hanging when this "measurement" was taken. This is an IRS car so compressing the suspension won't change anything. The mark actually represents where the seal is. It's probably very close to half way engagement.

Taxman20

iTrader: (11)

Ok, I see. Yea your rear center section stays where it is. Depending on the power you are making, you should be ok. Its not going to move out more than it is now since nothing is going to move. But if you make a bunch of power I would get it in as far as possible.

forcd ind

iTrader: (7)

depending on the trans, some of the output shaft sticks out past the seal, so you actually have more spline than a seal might show
Stick the yoke in all the way, then meas how much you pull out to hook the shaft up
I shoot for around 3/4" pull out with rear loaded

oscs

iTrader: (19)

It's a glide with a GV overdrive unit. The seal sticks out further than the shaft. The pull out is around 1 1/4" out of a 3.5" total length yoke.

stevieturbo

When you see how little splines engage on either driveshafts/axles within the diff, or a clutch disc on an input shaft...

Really, whilst you could have more on that spline/yoke, it really is plenty.

And the axles/stubs/shafts receive far more torque than the output shaft of the trans does.

oscs

iTrader: (19)

Since I don't have to change a thing or spend any money I'm going to subscribe to this theory. Is it ideal? No. Will it work? Probably and I think I'm cool with that.

Forcefed86

iTrader: (4)

That's fine IMO. I actually had a similar situation and ordered a longer yoke instead of modifying the driveshaft.

oscs

iTrader: (19)

The more i look at it the less im worrying about it. If my trans moves enough to cause an engagement issue here i have much bigger issues to deal with.

Project GatTagO

iTrader: (7)

Are you getting any vibrations? What can happen when the driveshaft is too short and there isn't enough spline support to stabilize the yoke, the front u-joint can start "jump roping" which will cause a vibration. With an IRS car, I would want that yoke in as far as possible and leave 1/2" before the yoke bottoms out against the output shaft.

Also, do the splines inside the yoke extend all the way to the front tip of the yoke? I bet not.

Andrew

coltboostin

Mine has less engagement than that-I was concerned at first, but it does not vibrate and has held up to the abuse I have put it through thus far, so I have stopped worrying about it.



Thats a great point! I will have to take a peek next time I have my D shaft off

oscs

iTrader: (19)

The splines run the length of the yoke. Why would you want extensive engagement on an IRS car? the Diff is fixed to the car and has zero travel.

Project GatTagO

iTrader: (7)

It's the other way around. I want to take advantage of that fact that it is IRS to get as much spline engagement as possible.

Andrew

oscs

iTrader: (19)

Gotcha, I think i have enough engagement at this point though.

Shownomercy

iTrader: (1)

Since you are not concerned with movement you can take advantage of having more spline engagement and lesson the chance of twisted splines etc. That is what I would guess he is getting at.

coltboostin

Makes sense.

Also makes me want to investigate mine further.

oscs

iTrader: (19)

Ahhhh ok lol! I see what he is getting at now.

stevieturbo

Really though, whether IRS or Live rear...either can get plenty of engagement.

Fore/aft movement on mine through full axle travel is only a few mm anyway

Project GatTagO

iTrader: (7)

I can confirm this. When I was doing some fitment testing on my 1970 GTO, I had the tail shaft housing off the trans. I installed the driveshaft and put a zip tie at the end of the slip yoke. Then I bounced the car as much as I could and also lifted it up as much as possible, and the zip tie moved about 1/8". Assuming there was more suspension travel when driving, on that particular car I doubt that the slip yoke moves more than 1/4" Also keep in mind that if the driveshaft and the pinion are mostly parallel to each other, as the pinion rises when power is applied, the yoke will actually move back, not forward. This will vary with different driveline angle arrangements, of course.

My latest Cougar build has this beauty installed:











The CV joints have some play in them and I don't have to be concerted about driveline angles anymore!

Andrew