Community Forums

geofferyh · 11-28-2020, 06:55 AM

Allison Auto 5-Speed Transmission, Model 1000 HS/MH/RDS/EVS s/n: 1S6310207106

2003 Holiday Rambler Admiral SE with Workhorse W22 chassis and GM 8.1L gas engine. I normally run at 62 mph and let the cruise control handle shifting under loading conditions. At an under load down shift point from overdrive there is now a slight hesitation, then typically 2 or three "pop, pop" sounds from engine, then normal climb back to overdrive cruising at 62 mph. However, happens most of the time, but doesn't happen all the time.

There are no "Check Engine" lights showing on dash. Had fuel checked, all good and installed a new fuel filter just in case.

I am now staying in an RV Park in Paducah, KY until I have some idea as to how to proceed to resolve this problem.

Very concerned. Ideas appreciated.

Skip426 · 11-28-2020, 12:46 PM

Any history of spark plugs and wires being changed ?

Plug gap set to the new spec? If the new spec applies to this year of the 8.1 .

2/3 miss fires might not meet requirements for a code or CEL.

Like it's bigger Allison transmission cousins , shifting of the 1000 series can be affected by engine performance.

geofferyh · 11-28-2020, 04:16 PM

Wires and plugs are original.

I don't see wires and plugs as the problem since the problem is only as outlined. If overdrive is not being utilized it seems to run just fine.

Flyer15015 · 11-28-2020, 04:31 PM

Have you checked your Tx fluid level ? If O.K. when is the last time you changed the fluid / filter ?
If it's downshifting "under load ?" are you using it for a brake ? or going up to 5th under load ? I don't get it ? Going up should be a smooth transition. Using it for a brake may cause her to "hic up".

Arch Hoagland · 11-28-2020, 04:31 PM

Quote:

Originally Posted by Skip426

Any history of spark plugs and wires being changed ?

Plug gap set to the new spec? If the new spec applies to this year of the 8.1 .

2/3 miss fires might not meet requirements for a code or CEL.

Like it's bigger Allison transmission cousins , shifting of the 1000 series can be affected by engine performance.

I agree. I'm on my third set of plugs and wires over the past 96,000 miles. Popping was the reason I changed them the last time.

Have you been changing the transmission fluid and filter every 25,000 miles or two year interval?

geofferyh · 11-29-2020, 08:28 AM

Thanks for the discussion guys.

If plugs or wires are suspect, why does it run just fine when transmission is not in "Overdrive" mode? Problem only presents itself when I apply more gas pedal to get back into overdrive after a down-shift.

Trans fluid was changed at 51,195 miles (20,769 miles ago). Last Spin on Filter change was at 68,971 miles (2,993 miles since change).

This motorhome has only been driven for the most part in fair weather, very few times when its rained and never during winter months. The exhaust pipes don't even have rust on them. I personally service the motorhome every fall before heading south. I follow the Workhorse service schedule and recommendations which include visual inspections. I have my own OBD Scanner, and can check codes if the check engine light were to be illuminated. Also, I run mid-grade fuel just so I do not get a knock-sensor tripping the check engine light due to low octane regular unleaded fuel.

Also, Skip please define "CEL" (Unknown to me)?

RetiredBob · 11-29-2020, 08:36 AM

CEL=Check Engine Light

twinboat · 11-29-2020, 10:32 AM

It can happen because stepping on the gas asks the loaded engine to do more.

With more load and RPMs you need a stronger spark, or closer plug gap, for it to jump.

Plug gap can widen as they age. Pull one and take a look.

geofferyh · 11-29-2020, 11:04 AM

Quote:

Originally Posted by twinboat

It can happen because stepping on the gas asks the loaded engine to do more.

With more load and RPMs you need a stronger spark, or closer plug gap, for it to jump.

Plug gap can widen as they age. Pull one and take a look.

In past, stepping on the gas asking the loaded engine to do more has produced a CEL, typically as a result of one of the knock-sensors (momentary audible engine pinging, not an audible "pop, pop, pop").

I think I will get out my OBD Scanner and check to see if there are some recorded engine or transmission codes that I don't yet know about. To be continued...

Skip426 · 11-29-2020, 11:51 AM

Transmission in OD and torque converter Locked Up is max load on the engine , the same condition that gave you the CEL due to the knock sensors , before you switched to mid grade fuel is producing the " pop,pop,pop" now .

geofferyh · 11-29-2020, 12:12 PM

Quote:

Originally Posted by Skip426

Transmission in OD and torque converter Locked Up is max load on the engine , the same condition that gave you the CEL due to the knock sensors , before you switched to mid grade fuel is producing the " pop,pop,pop" now .

Not sure I understand what your telling me.

Do I have a serious problem here? "Transmission in OD and torque converter Locked Up is max load on the engine".

Do you think I will find codes recorded, even though I do not have a CEL, when I connect the OBD Scanner?

Arch Hoagland · 11-29-2020, 01:53 PM

Read your Check Engine Light codes. They should be stored.

Have you ever cleaned your MAF?

geofferyh · 11-29-2020, 02:01 PM

Will read codes as advised in the next few days. Yes, MAF was cleaned at 64,329 miles (7,625 miles ago).

DiverBob57 · 12-06-2020, 08:39 PM

The OP posted this problem in Workhorse chassis forum as well. Indicated the wires and plugs have never been changed so they are 17 years old. I do not believe your problem is transmission related at all. The 8.1 Vortec has a history of burning plug wires due to high heat and low air movement in some doghouses.