Weird shifter problem

[Lin]

On this trip, we hit some grades that made me want to keep the Allison 647 in first gear.  It turned out though that my shifter has only five stops on it as if it was set up for a 3-speed instead of a 4-speed.  Therefore, I can shift down to 2nd, but no further.  The indicator shows 6 stops (R,N,D,3,2, and 1) but the mechanism does not match.  The tag on the shifter says it is Eaton-EPP Felsted, but I have not found any info on it.  It looks like it should be able to give me the extra 1/2 to 3/4" throw I need if I could find what stops it.  Does anyone know how to alter the setup on these things (or have a shifter already set up for a 4-speed)?

[kyle4501]

Do you have the mechanic's tips manual?

http://www.allisontransmission.com/servlet/DownloadFile?Dir=publications/pubs&FileToGet=MT1357EN.pdf

It doesn't detail the shifter it self, but it describes what the shifter should do & the range of motion at the transmission.


It is a big file, so it mayl take a while to download. . . .

[Lin]

To some this will be just esoteric information, but solving this problem has been interesting and it may be useful to those changing to an Allison, especially with a MC5.  I bought most of the parts for the job from Arizona Transmission in Tucson.  I had bought the shifter elsewhere from one of our beloved members (thanks Mike, for the help).  Well, it turned out that there is a different shifter required for the 740 series and 640 series transmissions.  The 647 actually needs more cable travel than the 740.

Well, we were lucky enough to get a nice deal on a new shifter from Direct Machinery, in Maryland.  I actually thought I was buying a takeout but it turned out to shiny and new.  I was truly happy to go install it expecting to solve the problem.  It didn't!  Although this shifter gave more travel, it still was not enough.  At this point, it decided to go to Kongsberg (they bought this part of Morse several years ago) for tech support, and they were very helpful.  I wanted to find out if the shifter I had may have been boxed wrong giving me the wrong part.  Much of these shifters are generic.  The difference being the detent plate and indicator.  They were able to confirm by the detent plate number that I had the right shifter.  The next question for them was whether the shift lever on the transmission itself was wrong.  My thought was the maybe the 647 needed a shorter lever which would increase the range of the throw.  Sure enough, they confirmed that I had the wrong panrail kit.  This, which did come from the rebuilder, was also for a 740.  The distance between the pivot hole and the attachment hole was 2.9 inch centers.  The one for the 647 was supposed to be 2.4 inch centers.

I spoke to the rebuilder who said he supplied that kit because he could not get the right one.  He thought that he had told us that so we would know that it had to be modified.  I suppose he just forgot to mention it.  I searched around for the right lever and did find one.  However since it was $30 bucks, I decided try to re-drill the one I had to see if it would work.  It seemed to make sense since I now knew where to get one if I ruined it.  I had been told it was case hardened and to expect to drill accordingly.  I removed it and drilled it destroying one bit and more burning through it than cutting through it.  I reinstalled it only to find that the other part of the kit, the cable hanger was also different and would have to be re-drilled too so the cable would be probably aligned.  I had hoped that it would have enough play, but it did not.  So, I removed the hanger and re-drilled it.  That at least was nice and soft.  I reinstalled that thinking that everything was covered, but was wrong again.  It did align properly and made all the shifts correctly.  However, when the lever is pulled all the way back into first, the housing is pushed very tightly against the side of the hanger and puts pressure on the shift lever.  It seems that to get it right, I would have to remove the hanger again and cut away a few inches of the side to allow the cable housing more freedom.

Anyway, since is was shifting adequately and it was 104 degrees, I decided to leave it as it is for now.  I do think it would be better to do the final step since the cable is being forced up against the shift lever more than it should be.  Did I mention that the shift lever is really hard?  I will just leave it for when I have some good ramps and cooler weather.

So what is to be learned here?  For MC5 guys the message is that the 647 requires different parts, even down the to shift lever, than a 740.  It is not that the parts are not available.  It is just that if you are unaware of it, you end up with extra nuisance.  The other thing is that, as logic would have it, cable throw is cable throw.  No matter how many times someone tells you to adjust the mountings of the cable housing, it does not change the throw.  I am sure you can figure out how I know this.