Transmission Failure

[duane m simmons]

Rob Teed
The transmission failure symptoms your are describing sounds like a
failure of the Governor. The governors have a wear out problem & will
not allow shifting into hi gear. The Manual describes an inlet & outlet
port test of 0.020" clearance. If you pull the governor & perform this
test, you may find your problem. About 80 to 100 k miles will wear out
the governor & the only solution is a replacement. If you have headers,
the left header will have to be removed to get the governor out.
Standard exhaust manifolds will allow direct removal w/o any difficulty.

Duane of Orange CA

 

[bob mclaughlin]

Duane,
I'd like to throw something on the table about transmission wear and see if
there is any actual experiences floating around. I had my transmission
governor removed and inspected at 100k miles. There was no discernable
wear. My mechanic then said if it was worn, it would indicate other damage
to the transmission and it would be only a matter of time before a full
rebuild would be necessary. I don't mean to spoil the day for anyone, but
has anyone had to replace the governor and then gotten another 50k miles or
so on the transmission?
Bob McLaughlin

- -----Original Message-----
From: owner-gmcmotorhome
[mailtowner-gmcmotorhome]On Behalf Of duane m simmons
Sent: Friday, July 14, 2000 6:29 PM
To: gmcmotorhome
Subject: GMC: Transmission Failure

Rob Teed
The transmission failure symptoms your are describing sounds like a
failure of the Governor. The governors have a wear out problem & will
not allow shifting into hi gear. The Manual describes an inlet & outlet
port test of 0.020" clearance. If you pull the governor & perform this
test, you may find your problem. About 80 to 100 k miles will wear out
the governor & the only solution is a replacement. If you have headers,
the left header will have to be removed to get the governor out.
Standard exhaust manifolds will allow direct removal w/o any difficulty.

Duane of Orange CA

 

[walt taylor]

> I'd like to throw something on the table about transmission wear and see if
> there is any actual experiences floating around. I had my transmission
> governor removed and inspected at 100k miles. There was no discernable
> wear. My mechanic then said if it was worn, it would indicate other damage
> to the transmission and it would be only a matter of time before a full
> rebuild would be necessary. I don't mean to spoil the day for anyone, but
> has anyone had to replace the governor and then gotten another 50k miles or
> so on the transmission?
> Bob McLaughlin
>
Couldn't swear about milage, but effectively, yes.

We may own the world's record, in that we have had two of the little
buggers seize and eat the gear off, apparently from a single errant
particle jamming up the slip rings. We have melted down one
transmission, and had another torque converter blow up, so have
contributed a fair amount of debris to the oil cooling system. When the
first isolated governor failure occurred, the transmission just had the
OEM filter, but reportedly had not had a transmission failure. The
transmission ran at least a few more tens of thousands of miles, and
didn't fail in that incarnation. It got a new clutch pack and a hard
shift kit, and then exploded the torque converter about 30,000 miles
later (convincing me that soft shifts and more frequent clutch
replacement was the better idea for trailer towing).

The second isolted governor seizure happened just a few months ago, and
we haven't run the GMC more than 2kmiles since then. By the time that
failure occurred, we had an external filter and a magnetic particle
filter in the external lines. Of course, the heat exchangers were
vigorously washed after each transmission failure.

The near-retirement-age counter man at the transmission specialty shop
that furnished the latest governor said, "Ya know, I been doin' this for
over thirty years, and I don't think I've ever had anybody ask for one
of these before [gov for a TH425]".

Don't know why we're so lucky with governors. We also replaced the
governor with one rebuild, but it was obviously hurting then due to
debris in the fluid.

Walt Taylor
Austin, TX
'75 Eleganza