Automatic Transmission Project hits a roadblock

[Fredward]

OK now that I've got the MT647 on the 8V71 and the new, five inch shorter driveline installed I see that the rear axle is going to interfere with the knuckles on the driveshaft. Now I understand why people have been saying that you need to shim the rear end of the engine. So I made 1" shims, but they are too tall so I'll have to take them down to 3/4".

The question is are there any options for a smaller profile driveline? Can I remove some material from the knuckle to decrease the chance of interference? Where can I find rubber body stops to limit the distance the axle can travel upward? Right now if I exhaust the air out of the air bags, the driveline contacts the axle housing.


Fred

[luvrbus]

I didn't use the flange I removed it and replaced the flange on the drop box with a yoke to make the shaft longer fwiw

good luck

[Lin]

Are the rubber frame bumpers still good?  Do you have good clearance when aired up?

[HB of CJ]

Will you have enough drive shaft length to allow the U-joints enough room to work properly?  Sounds like you shortened things quite a bit.  Also, like already said better, companion flanges usually add length, but you still need some way to quickly remove the aforementioned drive shift without having to unbolt and move big stuff.

Does your drive shaft have a sliding ability?  This means does it telescope?  What size U-joints are you using?  Will the angularity be within specs of the U-Joints?  Will the U-joints align properly?  Not much room for slop.  With some applications you may be able to use a smaller U-joint/shaft dia. which gives you more room.  HB of CJ (old coot)

[bevans6]

I'd restrict the movement of the axle both up and down, with bump rubbers, maybe move the engine forward an inch if I could, and see what happens.  If you have clearance when the bus is at ride height you should be OK.

Brian

[Brian Diehl]

Fred - I would go with Clifford's suggestion.  I also got rid of the flange on the end of my tranny when I did the conversion.  Going directly with a yoke off the end of the transmission gave me a drive shaft a few inches longer making it easier to get everything to fit.  This may be your solution as well.

[eagle19952]

I'd restrict the movement of the axle both up and down, with bump rubbers, maybe move the engine forward an inch if I could, and see what happens.  If you have clearance when the bus is at ride height you should be OK.

Brian

that may be, but what happens when an air bag blows....

[Tom Y]

Yes with Clifford and Brian. I left the flange at the dropbox but removed the one at the transmission. Tom

[bevans6]

Is it somewhat straightforward to replace the transmission output flange with a yoke?  Parts are available, etc?  The bump rubber idea is that if an airbag blows the axle can only move so far before it's supported with the bump rubber so you maintain minimum required clearance.

Brian

[eagle19952]

Is it somewhat straightforward to replace the transmission output flange with a yoke ?
yes.
Parts are available, etc ?
Yes.

The bump rubber idea is that if an airbag blows the axle can only move so far before it's supported with the bump rubber so you maintain minimum required clearance.
I would think both would be the best idea, a yoke and the bumpersBrian

[Oonrahnjay]

...  I would think both would be the best idea, a yoke and the bumpers  ... 

     For something that important, yes! 

[azdieselman]

Have a look at these. You can find a yoke with short ears, That will give clearance over the axle housing.
I had to redo my driveline when I installed the 7spd, I found the right combo of slip and shaft with enough travel.



www2.dana.com/pdf/J300-P8.pdf

www2.dana.com/pdf/J300-P3.pdf

[Fredward]

I still have the 1710 series sliding yoke and splined shaft with companion flanges that I had built. I'm currently in the test drive stages and had quite a bit of vibration to start with. I've shimmed the front of the engine 1" and the rear of the engine .500". The 1" was to get the drive shaft over the top of the axle. The .500" shim eliminated most of the vibration that I initially had caused by the 1" shim. Then yesterday I adjusted ride height down an inch or so and that change seems to have gotten rid of anything that I can feel. Interestingly, lowering the ride height helped with two things: it removed vibration and it keeps the rear knuckle from interfering with the top radius arm. (In retrospect the 1" shim under the front of the engine was probably too much.)

I purchased new MCI bump stops and am fabricating spacers to space those stops downward to stop the axle upward travel before it contacts the drive shaft. I will be welding those in place tonight. I'm still wondering about maybe running the driveshaft 90 degrees out of phase because there may some micro  vibrations that could cause problems long term but that cannot be felt? Working with a drive line angle calculator program to evaluate that.

The coach runs and drives like a million bucks. The transmission shift points seem good. I have not started tweaking the modulator adjustment but right now we have a trip planning this coming weekend and other than driving it around running errands, that will be our shakedown cruise. I'm really pleased with the outcome thus far.

[Utahclaimjumper]

 Fred, the picture may be a distortion, but the "U" joint "knuckles" do not seem to be "clocked" correctly, which will be VERY important with a shaft this short.>>>Dan (Or any length for that matter)

[luvrbus]

Good job Fred enjoy the clutch less world