Converting to manual transmission

[CHEESE_WAGON]

The MD3060 has the locked out sixth gear, not the 2000, AFAIK. Some of my older posts may have confused people as I was not clear about that at the time. The 2000 is a 5-speed auto with a lockup converter, AFAIK there is nothing to unlock on them.

OP, you can gain a measure of downhill control by simply downshifting from D to 4 (or 2, in extreme cases). It is pretty much the same effect as downshifting a manual, apart from an auto having a minor degree of slippage.

I think you are asking for a large headache trying to convert an automatic-equipped bus to manual, mainly because the engine's computer will likely be looking for a signal that isn't there anymore that may be crucial to the engine running properly.

Sure, you can have the ECM reflashed, but in the end I think it will be more trouble than it is worth. A good trans retarder / engine brake / jake brake setup on a T444 would likely give you all the downhill control you need, even with an auto trans, and probably a hell of a lot less trouble and cheaper than a manual swap.

However, if you absolutely insist on doing this, any manual from a Navistar truck series 3200-4900 should work, just be damned sure to get every last bit of linkage, hardware, clutch master, driveshaft, because you will likely have to change everything that has anything to do with the driveline or trans.

[Dirtdoctor]

What Allison transmission do you have? Take it to a Allison dealer and tell them you want 6th gear “enabled”. One of my trucks came with a 5 speed . But the same transmission was in a cement truck that was a 4 speed. I went to Allison and they turned on my 6th gear. Computers are amazing.
Don’t do
The swap. The computerized Allison’s are set to maximize power and fuel economy.
See your dealer.
Cheers

[Booyah45828]

I wouldn't recommend a 2 speed rear axle.

A few decades ago there was a terrible school bus accident in Colorado(?) Because the driver tried to shift the rear axle while going down hill, broke it in the process, giving him nothing but neutrals, and then overheated the brakes trying to stop it. They eventually stopped at the bottom of a canyon, killing several kids on board.

After that incident, It was recommended to not shift the 2 speed axle's while moving, and 2 speed axles honestly became a thing of the past.

Furthermore, most 2 speeds were used in gas powered vehicles. So the typical ratios you'll find will be 5.xx and up, making them pretty useless for diesel folks.

[RolesvilleMarina]

Originally Posted by Free Bird

If you can do 60 (without lugging) at under 2000 rpm you're golden!

When I did my AT545 to Allison 2000 swap I was running originally at 2400 to get 57mph with the AT545. Now I did learn that fresher fluid I prob would have gotten better performance, so lets say I topped out max rev and speed at 60mph.

I have a 4.78 rear end and I keep the cruise set at 64mph and I am running 2050 RPM on the T444E now that I have the Allison 2000 in our 7 window Vista

My top speed is a bit over 75 but I stopped accelerating about there and was at 2300..so not much more, and I would be pushing the motor and I treat her better than that.

I recently pulled our 18ft Stingray behind the bus and on moderate grades on the highway (hills, not mountains) I didn't lose any speed and held 64 and 62 on the worst hill.


I agree that a 64mph top is ideal, mostly as when everyone else is doing 70+ you can set cruise, keep a good clip, and a wide open highway in front of you.


As far as the two speed rear ends I did some research into this, as a manual swap was next on the list if my 2000 swap wasn't going to happen. I found that most of the split rear ends were mostly dump trucks or the like and offered a choice of short, and then shorter.

Stupid question, but one would have to have a manual to run a split rear end? Could it be done on an automatic Transmission by shifting to Neutral for the split?

I've run them in manuals, been a long time ago. Never heard of one breaking like that... those poor kids, but I also wonder what the specifics were...I don't think this is that common a thing, or is it?

But, in the end if I could run a split rear, with a 4.78 what would be the ideal number to match to that in a split rear? I know it doesn't exist, and its highly unlikely it could be done with an auto. But curious what would pair well with a 4.78

or what combo would be ideal in a "perfect split rear"

[s2mikon]

Many years ago when I worked at a shop that did a lot of dump truck conversions we would install 2 speed axles in 6v53 Allison transmission equipped trucks bought from state auctions. You can’t split gears because the split in the rear axle is the same split as the transmission, 1.4 to 1. So it was basically 1 extra gear. Depending on what was needed you could go up or go down ratio wise. To shift them we bought a kit at Allison that consisted of an electric solenoid normally closed an orifice and some hose. Then you would connect the line pressure port to the governor port. When activated it would hold 4th gear lock up. This kit was very popular for power tower applications and fire pumpers with split PTO’s. To shift you would have to be in high gear push the solenoid button and shift the axle up release the throttle press down again and release the bypass button. And the reverse going down. This made it nice to come out of the granite pit in low range and wind it up in 4th and then shift up for the highway. Those 6v53 engines were kind of weak in the torque department but were very reliable and economical to rebuild. There was also a kit used for converter lock up in neutral for PTO use. We also did the HT 740 lock up over ride for the Jake brake installs too. Now days they are all electronic so I have no idea how you would do it.

[rossvtaylor]

Originally Posted by Dirtdoctor

What Allison transmission do you have? Take it to a Allison dealer and tell them you want 6th gear “enabled”. One of my trucks came with a 5 speed . But the same transmission was in a cement truck that was a 4 speed. I went to Allison and they turned on my 6th gear. Computers are amazing.
Don’t do
The swap. The computerized Allison’s are set to maximize power and fuel economy.
See your dealer.
Cheers

This sounds very easy...but my experience with several vehicles (both buses and ambuli)...is that the dealer won't do this without an authorization letter from the manufacturer. I'm still waiting for such an authorization letter from Gillig and Freightliner was no help at all. There are "rogue" individuals out there who will perform the unlock, but getting an Allison dealer to do so has not been an option...in my experience.

[RolesvilleMarina]

Originally Posted by s2mikon

Many years ago when I worked at a shop that did a lot of dump truck conversions we would install 2 speed axles in 6v53 Allison transmission equipped trucks bought from state auctions. You can’t split gears because the split in the rear axle is the same split as the transmission, 1.4 to 1. So it was basically 1 extra gear. Depending on what was needed you could go up or go down ratio wise. To shift them we bought a kit at Allison that consisted of an electric solenoid normally closed an orifice and some hose. Then you would connect the line pressure port to the governor port. When activated it would hold 4th gear lock up. This kit was very popular for power tower applications and fire pumpers with split PTO’s. To shift you would have to be in high gear push the solenoid button and shift the axle up release the throttle press down again and release the bypass button. And the reverse going down. This made it nice to come out of the granite pit in low range and wind it up in 4th and then shift up for the highway. Those 6v53 engines were kind of weak in the torque department but were very reliable and economical to rebuild. There was also a kit used for converter lock up in neutral for PTO use. We also did the HT 740 lock up over ride for the Jake brake installs too. Now days they are all electronic so I have no idea how you would do it.

interesting



YES!

So you've run split rear on an auto trans?

[s2mikon]

Yes I have. Like I said you can’t split the shifts because of the ratios in the planetary gear sets in the 2 speed rear axles are the same as the planetary gear sets in the transmission. It just became 1 more gear. If you didn't use the lock up it was very easy to find a bunch of neutrals. Allisons were very road speed sensitive so if the drive shaft slowed down because the 2 speed got caught in the middle and did not finish the shift it would go to first gear. This would make a hell of a racket and you would have to stop and start over. If I remember right we used 5.14 / 7.20 ratio for the dump trucks. These were all 2 axle air brake short trucks for tight construction jobs. All highly overloaded. But it worked. These were also used on hillsides to sand fruit tree orchard roads. Hence the Allison transmissions. Manual transmission clutches couldn't take the abuse.

[s2mikon]

Ross, Some of the oil field trucking companies here have purchased highway trucks from major freight companies at auctions to use as oil field trucks that were road speed governed to 63 mph and when they took them to the dealers to have them turned up they refused and told them it was a liability thing. So they took them back to their shops and installed 24.5 wheels and 11 r 24.5 lug tires. The speedometer is now off but they run 70 mph now. I’m not condoning this because they are also cheating on road tax too. Something I would never do. Make a cheat sheet on the dash and move on.