Trans acting funny in truck

chromebumpers

chromebumpers

solid fixture here in the forum
Staff member
Everytime I come to a stop it feels like I have a trailer behind me with a weight shift bump or it feels like the car behind just tapped me. I had a 50lb. spool of wire in a milk crate in the bed and originally thought that was sliding forward hitting the front of the bed but it's a stronger hit now.
Have you ever heard this before? Any suggestions where to start investigating? This is the Allison Trans.
 
have you inspected the trucks u-joints yet?
 
No, I wouldn't normally think of them at just 60,000 miles, but U-joint play would feel like that. I'll check them out.
 
It could be a problem with The Allison Transmission.
Diagnose with a Tech 2 scanner if need be.
I have repaired a few Allison Transmissions.
And replaced at least 7 in the last 5 years.
 
I just put the truck up on the lift today. The u joints look ok. I grabbed and turned both main shaft and front drive. The rear diff to drive shaft has a slight play in the (pinion gear?) But other wise I can't find a problem yet. I'm changing the oil/filter and the spin-on/off trans filter and I need to see if there is a drain plug for the trans, if so I'll drain and refill with Moble 1 Synthetic ATF and see if it's any different. Any reason I should pull the rear diff cover?
 
Check the Rear Diff gear oil.
I don't think the rear diff is at fault.
Problem with the Allison trans.
A bad shift solenoid or more.
ATF change Ok. Worth a try.
Will take a professional mechanic like myself to diagnose correct .
 
Nah, we worked often on allison transmission... the wiring harness go bad 90% of the time.. sometime its also the internal wiring. Or a dirty/sticky body valve.
 
mathd said:
Nah, we worked often on allison transmission... the wiring harness go bad 90% of the time.. sometime its also the internal wiring. Or a dirty/sticky body valve.
Click to expand...
Richard has no clue .
 
Brian, we all have our niche in life. I don't go around telling people they don't have a clue
about computers. We need to stay more upbeat and positive with our comments. There
are plenty of things I have no clue about and I know that before anyone tells me.
 
Indycars said:
Brian, we all have our niche in life. I don't go around telling people they don't have a clue
about computers. We need to stay more upbeat and positive with our comments. There
are plenty of things I have no clue about and I know that before anyone tells me.
Click to expand...
Its obvious by Now Richard is Not an ASE Master Mechanic like me & I have been at it a very long time.
Richard is a Money Maker.
What he does best.

People don't like the truth.
I must always Sugar Coat and Lie.
Gets Old.

Comes down to 1320 feet in my worls here in Illinois .
12am -3am.
Hp at 800-2000 does not always win.
Best Car and driver does.
No bench race.
Real Racing.
 
I already stated the best way to troubleshoot the Allison is with a Tech 2 scanner or Similar .
Must understand data and how to diagnose from it.
Very advanced at times.
Other times problem shown immediately .
 
I try what I can And learn as I go. The trans shop is 20 miles and a 2 week wait, dealers are 10 days or more. Everything inbetween is franchise tire/repair shops. Only the fast, easy repairs get seen within the same week inspections, brakes, oil changes and A/C jobs. This is a good place to be a mechanic and likely why everything on CList needs repairs and cheap Lol.
 
I have a snap on Scanner, I feel stupid asking but will computer controlled transmissions show codes on OBDII?
 
chromebumpers said:
I try what I can And learn as I go. The trans shop is 20 miles and a 2 week wait, dealers are 10 days or more. Everything inbetween is franchise tire/repair shops. Only the fast, easy repairs get seen within the same week inspections, brakes, oil changes and A/C jobs. This is a good place to be a mechanic and likely why everything on CList needs repairs and cheap Lol.
Click to expand...
What you want to Monitor check is The Park, Reverse, Drive Range & Down to Low1 range.
Should be in Transmission data.
Sometimes repeated in Engine data.

Trans Data....
1-2 Shift times.
2-3 Shift time.
3-4 Shift Time.
4-5 Shift time.

Line Pressure control duty cycle.
About 90-96 -100 % at WOT.

INPUT SHAFT RPM.
OUTPUT SHAFT RPM.

TCC LOCKUP TIME & DUTY CYCLE.
TRANS TEMP.
BATTERY VOLTAGE.

APP1
APP2
APP3.
3 TPS Potentiometers built into the gas pedal.

Hard because its your 1st time.
I WAS THE ONLY AUTO TRANS EXPERT ON DC.
 
While looking up which spin-on filter I need for the Allison I noticed there was a flat internal filter also available. Does my '06 have 2 filters?
 
Buy the spin on.
There may be another filter inside.

Large Diesel Allison Semi truck trans has the Large Flat filter inside.
Cummins 8.3 -11.0 Liter engines.
 
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