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Transmission Not Engaging and then Lurching

After traveling on the interstate for about 2 hours got off and drove some city streets.  Transmission was working flawlessly on the interstate; however, when driving the city streets while taking off from a red light, the transmission would slip (not engage) right away.  On one occasion, the RPM went up to 2k but the transmission would not engage, reduced RPM and it finally engaged.  Once engaged it shifted gears ok.  Another time on a hill, the RV started to roll backwards before engaging.  I got scared and pulled over into a parking lot and have had the unit towed to an Allison dealer.  They can't look at it until Tuesday but would welcome comments on what I might be dealing with.

A little background: I just had the coach fully serviced two weeks ago which included replacing the transynd with new transynd (Mobile Delvac) and replacing the filters.  We've been on a trip for about 2 weeks and have traveled about 2,000 miles.  As you might remember, I had written earlier about the fluid levels reading differently between the keypad (down 2) and dipstick (ok).  I added one quart and keypad was ok and dipstick showed just a little over.  I spoke to an Allison rep and he said that was not an issue.

Initial comment from Allison service manager was it sounded like I needed a new transmission which seems bogus to me ... any thoughts?
Jimmy

Margie and Jimmy
2003 U270 36' (one slide)
1998 U295 36' (Sold 2019)

Re: Transmission Not Engaging and then Lurching

Reply #1 –
Jimmy,

Did you try checking for stored transmission trouble codes?

Allison Transmission Codes Manual

Do you have the operator's manual for your trans?  Should have a trouble shooting section.  Here is link, if needed:

http://www.rvtechlibrary.com/transmissions/3000_4000_operators.pdf

Wish I could be more help, but this is a new one on me.  Back in the day, auto transmissions would start slipping if you let them get low on fluid, but it sounds like you have ruled out this possibility.
1993 U280 SE 40' WTBI, Build: 4359
C8.3 300hp, 6-Speed, Exhaust Brake
960 watts on the roof (6 x 160)
Sorento (or BOLT) on a Kar Kaddy SS
"Nature abhors a vacuum"

Re: Transmission Not Engaging and then Lurching

Reply #2 –
Quote from: jimmy_walther –
Initial comment from Allison service manager was it sounded like I needed a new transmission which seems bogus to me ... any thoughts?

Jimmy,

If you can drive it I would look for another shop. Sounds more like a bad speed sensor or bad wire to the speed sensor. There should be a code in the computer that a quality shop would pull before making an assumption that your transmission is shot. I would hope this isn't a Stewart& Stevenson as that is who I would try to get to if at all possible. Stewart & Stevenson | Home

Pamela & Mike
Pamela & Mike 97 U 320

"It's not what happens to you, but how you react to it that matters."

Re: Transmission Not Engaging and then Lurching

Reply #3 –
Sorry, I should have noted earlier, no codes on the keypad.  Also no Stewart & Stevenson in Georgia (Atlanta) where I'm stranded.  I called several places that were on the Allison website and they all recommended the shop I took it to.

Interesting comment about wire to speed sensor, when I had the transmission serviced two weeks ago, I was having a problem with the temp gauge not working and they said the wire had become corroded, so they put a new connector on it, maybe the speed sensor wire is similar.  Hopefully when the actual mechanic looks at it, he will find something simple like that.
Jimmy

Margie and Jimmy
2003 U270 36' (one slide)
1998 U295 36' (Sold 2019)

Re: Transmission Not Engaging and then Lurching

Reply #4 –
Jimmy,

If it comes to disassembly I would want to closely inspect any "O" rings or seals that were replaced during your last maintenance. If a small chip was cut out of one on reassemble and that chip has settled in a valve or small metering port that could affect the hydraulic operation of your transmission.
John Duld
1995 U320C SE 40'

Re: Transmission Not Engaging and then Lurching

Reply #5 –
Or possibly incorrect fluids were installed?
"Riding and rejoicing"
Bob
1997 U320 40' Mid entry, build 5132,  wtbi ce27, 4th owner
2007 Solara convertible
2 prodeco tech outlaw ss electric bikes

1095 watts solar
08 Ls 460 and a sc430
2000 Ford F-250 superduty 4x4

Re: Transmission Not Engaging and then Lurching

Reply #6 –
On-Highway Fluids
Brett Wolfe
EX: 1993 U240
Moderator, ForeForum 2001-
Moderator Diesel RV Club 2002-
Moderator, FMCA Forum 2009-2020
Chairman FMCA Technical Advisory Committee 2011-2020

Re: Transmission Not Engaging and then Lurching

Reply #7 –
W W Williams is a nationwide business that has good reviews on both the Bus Conversions Board and the Wanderlodge Owners Group Board. They have  a shop in Atlanta.

TOM
SOB (Some Other Brand) division
1995 Wanderlodge WB40
8V92 :D

Re: Transmission Not Engaging and then Lurching

Reply #8 –
Sales + Service Locator

Here are shops in ATL.
I assume you have already checked fluid levels, connectors, and verified that what you are feeling is not engine hesitation but really is transmission.
I am 25 Miles East of ATL off I20 , call me if I can help.
Gary B  770-595-3891

Re: Transmission Not Engaging and then Lurching

Reply #9 –
Quote from: wolfe10 –
On-Highway Fluids
Good info, thanks, Brett. Can those approved fluids be 'mixed & matched' in case I'm in Podunk and need fluid?  ^.^d
1993 U-240 "La Villa Grande"..CAT 3116 w/ Pacbrake PRXB...Allison 3060 6-speed..
Previous: 1983 Airstream 310 turbo diesel, 1979 Airstream 280 turbo diesel
                                      Build # 4297
                                      PNW natives
                      Home base:  'Cactus Hug' (Ajo, Arizona)
                        DW Judy & Chet the wonder dog
                        Full-Timers 'Sailing the asphalt sea'

Re: Transmission Not Engaging and then Lurching

Reply #10 –
Mike,

Past my pay grade.  I ASSUME they are compatible, but hard to imagine a place where you could not get Allison fluid.  Allison has the lion's share of the HD automatic business in N America, so lots of dealers and also shops that service them.

I always carry a spare gallon of all fluids in a Rubbermade tub.  Never a question of compatibility.
Brett Wolfe
EX: 1993 U240
Moderator, ForeForum 2001-
Moderator Diesel RV Club 2002-
Moderator, FMCA Forum 2009-2020
Chairman FMCA Technical Advisory Committee 2011-2020
 

Re: Transmission Not Engaging and then Lurching

Reply #11 –
Check the level,add 2 qts and see if the symptoms change .