No shift transmission problem resolved

RF_Burns

RF_Burns

Super Moderator
Staff member
Sep 7, 2008
5,146
1,343
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Ontario Canada
If you recall back in June I wrote about my transmission not shifting from first to second. This has been an intermittent on-going issue since I put
this rebuilt transmission in about 10 years ago. Usually happened 2 or 3 times a season, but more frequently in the last couple of years. I could
always pull it into 2nd and it would shift up, then back to drive and it would shift to 3rd so it never left me at the side of the road, but it did
ruin several trips over the years... cut short or cancelled. This year however it would not shift automatically most of the time.

I'm the type of guy who needs to understand how everything works and needs to troubleshoot down to the exact cause of a problem so I know its fixed.
But the hydraulic shifting in an automatic transmission is something I can't get my head wrapped around. So I ended up taking it to the local GMC
Motorhome expert, Borrmann's Garage.

Frank looked it over and could not find anything obvious, but the line pressure would drop dramatically in 1st and second but was normal in 3rd and
reverse. so he pulled it and sent it to his tranny guy. His tranny guy found a worn boss where a seal rides. They found a good replacement for this
part (sorry I can't remember exactly what this part was... Chemo brain fog again). He also found the front band was badly worn. He rebuilt the
transmission and sent it back to Borrmann's. Frank re-installed the transmission and took the coach for a test run... no good, same thing.. no
automatic shifting. Same low line pressure.

So the transmission was pulled again and sent back to the transmission shop. Again they inspected the transmission looking for why the pressure would
drop but could not find anything. Frank had a good core transmission so he sent that to the tranny guy. Since my internals were good with new bands,
clutches etc, they moved everything over to the core transmission and rechecked everything. Frank installed this transmission and all was good! So
somewhere in my transmission housing there must be a crack or porous aluminum causing a major leak.

I picked it up last weekend and it shifted properly on the 120km trip home. Hoping that is the last of that problem!

Thanks to Frank Borrmann and his transmission shop for fixing this issue!

--
Bruce Hislop
ON Canada
77PB, 455 Dick P. rebuilt, DynamicEFI EBL EFI & ESC.1 ton front end
http://www.gmcmhphotos.com/photos/showphoto.php?photo=29001
My Staff says I never listen to them, or something like that
 
When I was with Ford Motor co, we ran into couple transmission issues that
could not be solved at the dealership level, so we would ship it to
Dearborn and they would do series of tests and finally figur out what was
causing the intermittent behavior.
My head Boss, hated these issues as this went against our warranty costs.

On Sat, Sep 5, 2020 at 7:19 AM 6cuda6--- via Gmclist <

> Excellent to hear Bruce!!
> --
> Rich Mondor,
>
> Brockville, ON
>
> 77 Hughes 2600
>
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>

--
Jim Kanomata
Applied/GMC, Newark,CA
jimk
http://www.gmcrvparts.com
1-800-752-7502
 
A lesson to learn. Always check things before departure.

A GMC friend recently called me from the road to say that his coach had suddenly dropped out of third gear and into second and would not upshift. We
talked and he had tried wiggling the lever. I asked when he had last checked the fluid level and he was sure it was recently.

So, the next simple cause on the list is the modulator line leaking. I talked him through disconnecting that at the carburetor base and sucking on
it. It held solid.

I was running low on cheap and simple fixes, so I asked him to check the fluid level again. It didn't show on the stick. Fortunately, he did have
about a pint in his onboard stock and that was enough to make it shift again, but it was still way low. When we parted he was going to go by a parts
place and get another bottle.

Matt
--
Matt & Mary Colie - Chaumière -'73 Glacier 23 - Members GMCMI, GMCGL, GMCES
Electronically Controlled Quiet Engine Cooling Fan with OE Rear Drum Brakes with Applied Control Arms
SE Michigan - Near DTW - Twixt A2 and Detroit
 
What I do befoer a long trip, I drop the pan and examin the debri
at bottom of the pan,
Should it have sparkly sediments, then I know I need to see why.
Also keep in mind that the fluid need to be changed more often than a car
as there is lot of lead not only the weight, but the Aerodynamic drag

On Sat, Sep 5, 2020 at 11:56 AM Matt Colie via Gmclist <

> A lesson to learn. Always check things before departure.
>
> A GMC friend recently called me from the road to say that his coach had
> suddenly dropped out of third gear and into second and would not upshift.
> We
> talked and he had tried wiggling the lever. I asked when he had last
> checked the fluid level and he was sure it was recently.
>
> So, the next simple cause on the list is the modulator line leaking. I
> talked him through disconnecting that at the carburetor base and sucking on
> it. It held solid.
>
> I was running low on cheap and simple fixes, so I asked him to check the
> fluid level again. It didn't show on the stick. Fortunately, he did have
> about a pint in his onboard stock and that was enough to make it shift
> again, but it was still way low. When we parted he was going to go by a
> parts
> place and get another bottle.
>
> Matt
> --
> Matt & Mary Colie - Chaumière -'73 Glacier 23 - Members GMCMI, GMCGL,
> GMCES
> Electronically Controlled Quiet Engine Cooling Fan with OE Rear Drum
> Brakes with Applied Control Arms
> SE Michigan - Near DTW - Twixt A2 and Detroit
>
> _______________________________________________
> GMCnet mailing list
> Unsubscribe or Change List Options:
> http://list.gmcnet.org/mailman/listinfo/gmclist_list.gmcnet.org
>

--
Jim Kanomata
Applied/GMC, Newark,CA
jimk
http://www.gmcrvparts.com
1-800-752-7502
 
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