Planet rebuild kits are readily available from Allison. I would think
Ti or Gama TiAl would be the way to go for the planet carrier. Better
fatigue resistance and lighter than the steel. There is one transmission
that has a 3.5:1 low gear without being compound. I think it is a MT640.
Dale Davies
If you could get some pictures of those parts I would love it.
Would they sell one planet gear and shaft?
That would cut the cost as the complete planet carrier is expensive.
Paul Lamar
The Allison MT654CR has a 4.17:1 first gear reduction ratio.
Does max input power play a role here? The MT640 is rated for a
maximum 250 HP and 640 lb-ft. The MT654CR is rated for 300 HP and 780
lb-ft. A newer Allison HD4070 is rated for 465 HP and 1465 lb-ft of torque.
The parts are far more expensive for older transmissions like the
640 and 653/4. A modern Allison 2000 P1 gear set from a Chevy Silverado
(3.51:1) is $320.11 from my local Allison dealer, vs $880.50 for the
same set for the older MT653. From a junkyard, a Chevy Silverado
transmission is $100 if you pull it yourself.
Dave Klingler
Power is a function of RPM. When designing a gear box torque is the
main criteria.
Those ratios are not representative of the planet carrier alone.
They are combined from
several gear sets. I would need pictures of the parts looking
straight down with the
planet carrier sitting on a bench top or on the floor.
Paul Lamar
I do not have photos of the parts. Local Allison distributor should be
accommodating. Just do not mention AC use.
The MT654 transmission is a 5 spd that has an extra planetary assembly
bolted to the rear of the case that gives the 4.17:1 ratio. That is
compound through two planetary assemblies. Not what you want.
Some of the Allison transmissions for the Chevrolet 2500/3500 trucks
were designed and I think manufactured by Allison and then turned over
to Chevrolet/GMC who then looked after parts, service and warranty.
These transmissions may be difficult to obtain individual planetary
components.
When you move to the Allison transmissions built and sold for medium or
heavy duty truck applications they handle the parts themselves. Those
you can get individual components. For some of the newer model
transmissions they may have 3.5:1 first gear in one planetary to go with
taller final drives. Most of the new transmissions also have one or two
overdrive ratios.
Dave, have you enquired as to the cost and availability of the HD4070 parts?
The MT 654 has essentially the same parts for the planetarium that give
gears 2 to 5 as the components in the MT 640 series transmissions. The
higher power ratings are achieved by having an extra pair of clutch
plates for more friction area.
New long haul engines are 500 to 600 HP. At 2100RPM they may be 1450 ft
lbs, but where most are geared to run at 1300RPM they will be 450HP and
1800 ft lbs. That is where the higher cost can come in. However if you
can buy the planet kits as you can for the older transmissions, the cost
would come down. The sun and ring gears are large and heavy and
expensive. But if you want bullet proof high HP capability that is what
is required. When planet kits can be purchased with the gear and shaft
an AL or TiAl Gama planet carrier can be machined to save weight.
The 2000 series from wrecker would be a good deal with the 3.5:1 ratio.
That would allow 10,500RPM for takeoff or racing with a 3,000RPM prop
speed. I doubt you could hurt the planetary set with 900ftlbs torque.
Dale Davies
When Paul asked whether the gears and shaft were available separately, I
figured googling and phoning the Allison dealer were something I could
do to help out. I didn’t ask about the 4000 series, but I did ask about
the MT640, 654, 1000 and 2000. The 654 wasn’t in the system, but the
salesman did show the 653.
It turns out Allison has a tough time looking up anything without the
serial number off an existing transmission. I was going to call the
factory and ask more questions, but I needed to go back to work.
Dave Klingler
There are several wholesale transmission parts suppliers in the US. They
will sell to you
if you have a business. They also sell Allison spare parts.
Make friends with your local auto transmission repair shop and get them
to order
the parts you need. Some have a great selection of used parts in good
condition as well.
I paid $100 for the Allison 3:1 planetary I have from an autoTX shop.
Paul Lamar
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