Frac pump transmission Problems

1. How to Trouble Shoot Frac Pump
Transmission Problems
David Aakre
Technologist

2. Allison Pump Transmission

3. Other Side View of Allison
Transmission

4. Allison Make and Model/ Gear Ratio

5. Solenoid Activated for Each Gear For
Allison Transmission

6. Solenoids to Check with Resistance
Meter

7. Solenoid Wire Pinched be careful
putting covers on and gasket.

8. Transmission not shifting in gears or
Stuck in Gear check solenoids
• Lock UP Solenoid when bad will cause the
transmission to heat up quickly and transmission
will not lock up. Never Run a Transmission that
does not lock Up (Burn UP Transmission)
• Measure solenoids with a Meter on Ohms usually
when transmission is still warm. 12 volt systems
solenoids should be 15-30 OHMS and 24 volt
systems 50 to 90 OHMS. I take average of all
solenoids and change the one that is higher than
the rest which is usually obvious.

9. Check Solenoid Relays, Can-Bus
• Depending on controlling software the solenoids might
be tied to relays such as in tier one Stewart &
Stevenson Models. Run through the gears on remote
box and watch relays toggle in proper sequence. Just
need main power on with remote box connected.
• Some pumps have Their solenoids tied to a
transmission can module. Programmed for that specific
type pump, Digital Can module 78. Most pumps are
can-bus to a Allison Control Module. Can-Bus 60 ohms
with two parallel 120 ohm termination resisters. If you
have can-bus problems measure resistors.

10. Relays and Transmission Module

11. Measuring Solenoid from Terminals

12. Transmission Pressure Switch
• The transmission Pressure Switch activates by
pressure (60 psi) when the rpms of the
transmission is around 1500 rpms. When the
switch closes you should have voltage to ground
on (NO) Normally open contact.
• If the transmission is not over heating but not
going into lock up, short out the connectors on
pressure switch. If it shows lock up you have a
bad pressure switch and change it out.
• A short will cause remote box to see lock UP
always. Change sensor or cable could have short.

13. Example of Pressure Switch

14. Transmission Filter
• Transmission Filter Sensor in my opinion is
always acting up and is always showing errors
even after you have changed sensor, cable,
and filters. Just keep on checking and ignoring.

15. Transmission Speed Sensor
• Usually the software you are using will give
you a transmission speed sensor error when
its bad.
• It is very easy to change and can be cleaned
first to see if that is all it needed.
• You can also use a PIE Meter or Frequency
generator to simulate through cable to remote
box or software to see transmission speed to
check cable and other connections.

16. Allison Transmission Speed Sensor

17. Allison Transmission Speed Sensor

18. Allison Shifting Recommendations

19. How to Manual Start Pump by pushing
in on Start Solenoid. Just a Tip

20. Other TIPS
• On Stewart & Stevenson Models you can cycle
the main power switch on and off real quick
without killing motor and it will reset remote box.
On and OFF on any electronics is a good idea.
Master Reset.
• Clear Transmission Codes on Control module and
your good to go most of the time.
• Stewart and Stevenson had the best pumps the
tricks listed fixed them most of the time and fluid
end is easy to work on.

21. Transmission Control Codes/ How to
Reset.

22. Allison Shift Selector.

23. Termination Resistors for Can- Buss. Two 120 OHM in
Parallel. 120 /2 = 60 Ohms for Can-buss measurement.

24. Example of Can-Buss

25. CAN-BUSS ON A FRAC PUMP

26. LINK TO ALLISON MANUAL ON NET.
http://vrcamping.com/_doc/articles/interet_general/mecanique/allison/
allison.pdf

27. DAVID AAKRE
TECHNOLOGIST
Allison Codes are listed all over internet and too large to put on power point.
All material listed on power point was made to public on internet and I used
it in my power point. Knowledge gained by 17 hr days on frac sights for 5 yrs.
A little information is sometimes all you need to fix something.