Trip Report + Mountain Driving + Tranny + Towing

[john wright]

I agree with Emery,
I suggest that you change the filter every 2 years in the spring or 16K
miles. Cheap insurance and I was told by a old GMC Mechanic that if you
take care of these transmission they will last a long time.

J.R. Wright
GMC Greatlaker
77 Eleganza II
Michigan

>
> In a message dated 7/22/99 10:58:37 AM Eastern Daylight Time,

>
> engine power and "bogging down" the engine. But from a dead stop, even in
> low, there is just no power. A small pebble in front of the RV might stop me
> cold. If the trans is loading up the engine, >>
> Larry - how long has it been since you have changed the trans fluid and
> filter? I suspect that your filter is clogged and that replacing it may
> solve your problem. This happened to me about 15 years ago and the
> transmission shop told me that I needed a rebuild at a cost of about $800 (in
> 1984 !!!), showing me the small metal particles in the pan. I told them to
> just change the fluid and filter. I/ve put a lot of miles on it since then
> and have no problems with the transmission. Just be sure to change the
> filter at the recommended time.
>
> Emery Stora
> 77 Kingsley
> Santa Fe, NM

 

[lorry clavelli]

> Emery, I wish that were it. My filter was changed about 4k miles ago, and
> refilled with Mobil1 ATF. But the lethargic performance from dead start, ......
>
> ............ Just seems like a matter of gearing to me, like trying
> to start out in 3rd gear on a manual shift vehicle.

- --
Larry,

It's possible that your problem may be in the last section of your email. Have
you checked the shift pattern to make sure that the transmission is really
stating out in 1st gear? Have you counted the shifts to make sure that your
transmission is going through the full pattern?

Lorry


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[mark grady]

Just some top of the head thoughts... and there isn't much up there...

Have you checked your tranny cable adjustment to make sure you're really in
drive and thereby starting out in first gear? Could your electric kickdown
switch be sticking?

Have you tried manually shifting to 1st gear to see if that makes a
difference?

It almost sounds like you're in second. I've never seen a TH-425 have a
second gear start, but... If you can find someone who knows these things, it
sounds like you've got a problem engaging first -- that's my guess. See if
you can manually shift this baby, keep it in first til 25~30mph or so.

Count the shifts, make sure you've got all three. Maybe you got a 2 speed
powerglide by mistake?

Perhaps one of our tranny experts will chime in with what causes this
failure. Only other thing that comes to mind (no low end torque) is a really
worn timing chain, or no accel pump action in the carb.

Git in and drive it like you stole it and see if that makes a difference. I
think you've maybe lost first gear.

Mark

|-----Original Message-----
|From: owner-gmcmotorhome
|[mailtowner-gmcmotorhome]On Behalf Of
|LNelson208
|Sent: Friday, July 23, 1999 12:18 PM
|To: gmcmotorhome
|Subject: Re: GMC: Trip Report + Mountain Driving + Tranny + Towing
|
|
|Emery, I wish that were it. My filter was changed about 4k miles ago, and
|refilled with Mobil1 ATF. But the lethargic performance from dead
|start, with
|the nose pointing to the sky, was apparent before the switch. All other
|aspects of engine power, vacuum, trans performance, etc. are
|great. There is
|just no reserve power "out of the hole on a hill". I wish a tranny expert
|would confirm my diagnosis that the trans IS transferring power to
|the final
|drive with minimal slippage, since the engine rpm really bogs down. If the
|trans were slipping, would not the engine rpm not be affected that
|much? Just
|trying to learn, here. Just seems like a matter of gearing to me,
|like trying
|to start out in 3rd gear on a manual shift vehicle. Oh, well.
|Thanks for the
|help and any more you can give. Larry in MO, PB 75

 

[wayne newland]

Larry

My 75 PB just flyes up the mountains of Western North Carolina. I realize those
are not real mountains that some people experience in the west, but some have
some steep grades. As far as I know, I have a stock trans and final drive.

Wayne Newland

> Emery, I wish that were it. My filter was changed about 4k miles ago, and
> refilled with Mobil1 ATF. But the lethargic performance from dead start, with
> the nose pointing to the sky, was apparent before the switch. All other
> aspects of engine power, vacuum, trans performance, etc. are great. There is
> just no reserve power "out of the hole on a hill". I wish a tranny expert
> would confirm my diagnosis that the trans IS transferring power to the final
> drive with minimal slippage, since the engine rpm really bogs down. If the
> trans were slipping, would not the engine rpm not be affected that much? Just
> trying to learn, here. Just seems like a matter of gearing to me, like trying
> to start out in 3rd gear on a manual shift vehicle. Oh, well. Thanks for the
> help and any more you can give. Larry in MO, PB 75

 

[wayne newland]

Having grown up in Kansas City (Missouri, of course) and having spent many
summers in the Ozarks (Scout camp at Osceola and fishing camp at Hurrican Deck
Bridge) I understand that you have some hills, too....and a lot of times no
chance to get a running start.

Of course, I don't know how much better an "improved" version might be, but until
what I have has to be replaced or I fall into an awful lot of sudden money, I'll
stay with what is there.

Wayne

> In a message dated 7/23/99 10:43:08 PM Central Daylight Time, wayne

>
> >
>
> Wayne, don't sell your "mountains" short. As for flying up the mountains,
> mine does fine with just a small amount of momentum. It is from the dead
> stop, steep grade, that I enter a high state of "pucker", and was glad that I
> wasn't towing. And this is in LOW. Keep thinkin' I need all the wisdom this
> net can muster. Larry in MO