Speedometer issue after AT545 to MT643 conversion

[cadillackid]

thats a thomas bus? is it a freightliner thomas? maybe i can call a dealer with a VIN and order one.. i cant read anything from that pic.. the fingers cover up anything useful..



all I can find on my end is a Kludge of screwing adapters together... i love that all-in-one solution.. I didnt realize you didnt have the part.. was hoping youd be able to take better pics of the numbers from it...

 

[NovaTRON]

thats a thomas bus? is it a freightliner thomas? maybe i can call a dealer with a VIN and order one.. i cant read anything from that pic.. the fingers cover up anything useful..



all I can find on my end is a Kludge of screwing adapters together... i love that all-in-one solution.. I didnt realize you didnt have the part.. was hoping youd be able to take better pics of the numbers from it...

It's a Oshkosh Thomas. I'll send you the VIN number (in a PM), but good luck, it seems rather hard to get any of the parts for this bus, as I believe it to be a rather obscure/ rare model, with most parts now being discontinued. From what I know, Freightliner handles all the Thomas stuff now.

Wish I had a better picture for you, that photo was sent to me from mechanic who's possession it is in.

 

[rtdillon1960]

If I missed this, mt apologies. Can you take the sensor out of the 643 and compare it physically to the 545 unit? If they are physically the same, install the 545 unit and check you readings. Just a thought.

 

[rtdillon1960]

For the cost of the trip could you pay them to pull the part and ship it to you? Just another thought.

 

[Crazy]

This is something I must worry about what's the changeover.

 

[Booyah45828]

I wouldn't worry about this. It's something that should have been checked/corrected while both transmissions were side by side on the ground.

It isn't difficult to fix, but would have been much easier while in the process of changing transmissions.

And it's pretty easy to check. Just remove the sensor and see what you have to work with on the output shaft of both, and then swap from the old to the new if you have to.

 

[cadillackid]

cal - yeah I mentioned it in my writeup.. when you buy a 643 it can be set up with either a gear or tone ring.. by 1990 all the internationals used a tone ring.. the LKQ units all seem to have slightly different navistar part numbers. but were designed to be diesel 2600 RPM units. which is whats needed.. technically on a DT360 a 2800 RPM unit could be used but that winds them out a bit..



however that said, the unit I got was supposed to be a tone ring and had a gear..



the ring can be pulled from the 545 and put into the 643 without complete trans disassembly.. theres a couple special tools needed to do it (which I own and can send to you should you need them).. but essentially you pull the rear seal (throw it away).. pull out a pretty massive snap ring.. use a wierd puller to pull out the rear bearing, then the spacer and gear or ring just slide off the output shaft...



reverse using a bearing install tool.. and a new seal. and done..



essentially if you shine a flashlight or bore-scope down into the hole where the speedo output is, if the "teeth" are i nthe same direction as the shaft (look almost like splines going alongthe shaft) then you have a tone ring.. if it looks like the "teeth" go across or around the shaft, thats a gear output.. the gear ouput looks like the pic this OP posted here...


-Christopher

 

[Wixtrix]

Need mt643 gear driven sensor part number

We just finished our at545 to mt643 swap. Only thing wrong is the speedometer won’t work at all. After reading this thread it looks like our mt643 probably has us set up for a gear driven speed sensor. I’ll have to go under and check. We got the mt643 from LKQ and did not come with any sensors. Since the ring tone sensor from our at545 screwed into the sensor hole on the mt643 I didnt think to look and see if it was gear driven. I think I need the part number for the gear driven sensor mentioned and picture in this thread. Any chance anyone has that? Or anyone know the best solution?

The speedometer is electric.

Thanks

 

[CHEESE_WAGON]

I'm not sure of this, but I wonder if the appropriate parts can be salvaged from the original AT545? The corresponding parts are usually installed on the output shaft, and I would think the output shaft would be a commonly interchangeable part between the two, or at least allow for the gear-driven / electronic sensor parts to be swapped out. If not, best bet is to contact Allison for the appropriate parts.

I did find a thread after my original post here alluding to some parts needed:

https://www.skoolie.net/forums/f33/parts-required-for-at545-to-mt643-changeover-28668.html

 

[cadillackid]

Yeppers they can.the tone ring can be moved from the 545 to the 643..
I remember somewhere I listed the steps to do it .. but basically you pull the toke (and park brake fluid f you have one) then pull the seal, then use a special allison tail shaft bearing puller and pull the tail bearing.. reach in and pull the spacer and the gear or tone ring. They just slide off the shaft easily.. swap .. put the bearing back in using the bearing install tool... install the seal .. and reassemble their park brake and or yoke.

I own the special tools if anyone needs them .. the bearing installer is heavy(8 or 9 lbs) so it might cost a bit to ship them.

 

[Wixtrix]

Thanks, I was hoping to find an easier solution, but looking at it today looks like swapping to the tone ring would be best. How long did it take to do this? Can It be done in a day? Or an afternoon of you know what your doing?

Unfortunately the old tranny is gone so I’ll have to order a new tone ring.

 

[cadillackid]

with the right tools its an hour or 2? you really dont disassemble the transmission at all.. it stays in the bus.. and you dont even lose much fluid.. installing the seal might be the hardest part simply because if you get it in crooked it will leak a little..


you can shine a light down in the speed sensor hole.. I cant find my speedo Gear drive to show you what it looks like.. I think I gave it to someone .. but I posted a pic of a tone ring.. if you look in the hole and see this type of "ridges" then you know the trans alrteady has a tone ring..



the tools to pull and install the rear bearing..



the wierd claw puller pulls the bearing.. the large cylinder like thing is the installer.. slide the bearing in.. and Beat the installer tool with a hammer and it presses the bearing back in..






-Christopher

 

[Wixtrix]

Thanks Christopher,
This is very helpful. I’m trying to debate if it’s worth doing myself or paying a shop a couple hours. The only reason I’m interested in a shop doing it is at the moment, I make more money when I’m working than it would cost a shop to do this. We are officially back on the road and currently in Oklahoma, not sure where to go next or where I could find a place to do the work myself, but I need to get the speedo and odo working ASAP.

One question, the mt643 obviously performs drastically different than the AT545. Should it be making a growling sound as it’s coming to a stop? I’m wondering if the modulator needs to be adjusted? Or if something else is going on. It doesn’t always make the sound when it’s coming to a stop, but it’s definitely in the tranny. It’s almost like driving a manual trans in too high of a gear and kicking it in to neutral . Or letting the rpm get too low on a manual trans in first gear. Any thoughts on that?

 

[CHEESE_WAGON]

Speed sensor is known to be a factor in transmission control, electric speedometers tend to increase the likelihood. CK can probably answer this more definitively.

 

[cadillackid]

on these the speed sensor doesnt control the trans at all, however the lack of speed signal to the engine could cause the engine to act differently not knowing that the bus is moving.. well i say that not remembering if you have a 12 valve mechanical or a 24 valve electronic 5.9..



the modulator adjustment is pretty easy to test.. if on the upshifts from a stop you floor it full throttle. and can reach 2500-2600 RPM before the trans shifts then the modulator is correct.. the exception being 4th gear which typically goes in around 2400.



if ther modulator is too loose it will shift much earlier and could leave the lock-up engaged a little longer on the slow down, you could get a bit of a growl if the 3-2 downshift and unlock is a little low..



if the modulator is too tight then all of your upshifts will seem "late" at part throttle.. light acceleration you'll find yourself "letting off" all the time to get it into the next gear.. signs of a modulator cable too tight...



im just assuming you have a cable modulator and not the electric one..

-Christopher

 

[Wixtrix]

Yes, it’s a cable driven modulator and it sounds like that’s what needs adjusting. It’s shifting too low and staying in higher gear at lower speeds. I think
I have that figured out, although it’s a little difficult to adjust on the Cummins 12v compared to others I’ve seen.

Last questions, do you or anyone else know the part number for that tone ring? I can’t find it and I’m looking to order one as soon as I have a part number. Alison wasn’t helpful at all.

Thanks agsin

 

[CHEESE_WAGON]

Yes, it’s a cable driven modulator and it sounds like that’s what needs adjusting. It’s shifting too low and staying in higher gear at lower speeds. I think
I have that figured out, although it’s a little difficult to adjust on the Cummins 12v compared to others I’ve seen.

Last questions, do you or anyone else know the part number for that tone ring? I can’t find it and I’m looking to order one as soon as I have a part number. Alison wasn’t helpful at all.

Thanks agsin

Try checking here....

https://www.allisontransmissionpart.com/allison_parts/page10.html

 

[Wixtrix]

Thanks I’ll look into this.

 

[Wixtrix]

After stumble into around looking for the modulator adjustment slide, I finally discovered that the modulator cable is attached to the accelerator pedal. There is no adjustment slide at all. The cable end was sticking out about an inch before the pedal would contact the cable. I discovered that by turning the nut at the end of the cable it shortened it down to 3/8 of an inch. That’s all it would go and still too loose. I then took the nut off and added 7 #10 washers to fill the space. Took it for a test drive and is drastically improved. It’s still shifting at 2300-2400 so I’m going to add a couple more washers and see what happens. Anyone familiar with this type of setup?

 

[cadillackid]

interesting.. mine has adjustment built in.. however ive done washers and nuts before on old cars.. you have the right idea