TH425 Filter Change

Chazzer

Chazzer

Member
Sep 11, 2012
83
6
8
Southern Ontario
Good Afternoon GMCneters,

Question for those that are familiar with the TH425 filter.

I went to swap mine out yesterday and had difficulties installing the new filter. I could not get it to secure in the mounting hole, even with two
o-rings on it. It was just flopping around.

I noticed the older filter has a longer mounting stem of 3/4" while the new filter is 5/8".

You can see the difference in this picture, existing on left, new on right.

I'm not sure if this is the reason it's not fully engaging, perhaps the taper is slightly off on the new on and it cannot slip into place.

I didn't want to force the new filter in place. The old filter pushes in and out of the mounting hole effortlessly and is quite secure and snug when
in place.

http://www.gmcmhphotos.com/photos/data/500/medium/TH425_filter_diff.jpg

Thoughts?
--
Jim Owens,

78 Royale,

Out skirts of Kitchener, Ontario
 
Jim, there have been several discussions on here about that very problem. It sounds like some
Brands of filter are being made with a too small tube. DO NOT use one that is too small.The tranny
Will suck air and 'blow' up.( not lierally) but it WILL wreck the transmission.
Measure the tube on your old transmiission filter with a dgital caliper and shop oround until you find a brand that fits
If your local Canadian Tire has one in stock, ask f you can measure it. If CTC dn'thave one, try
The local auto parts stores.
Has anyone one in Canada found a brand in Canada that fits properly?
--
DAVE KING
lurker, wannabe
Toronto, Ontario, Canada
 
I did read back through some posts concerning the subject, even before I started the operation. I was getting the impression it was the diameter of
the mounting stem and not the length that was causing issues, perhaps I misunderstood.

Diameter on both filter stems is exactly the same.

I had a fellow GMCer that is ready to do the same maintenance on his coach check out the specs on his filter, his being a Wix and this is a Power
Torque with part number FK-117. His Wix specs came back identical to this unit.

This unit was acquired in the USA and not here in The Great White North...

It's a mystery...
--
Jim Owens,

78 Royale,

Out skirts of Kitchener, Ontario
 
Jim,

I'm a bit confused at this point. To recap, your new filter and old filter
have exactly the same mounting tube diameter, but the new filter is 1/8
inch shorter. a couple of questions for you:

1) if you install the old filter, but leave it out the 1/8 inch, do you get
the same play as the new filter?
2) You stated that you did not what to force the new filter? I'm missing
something here, since if it is floppy....
3) Did you check the new filter for for roundness?

Rich

On Sun, Mar 29, 2020 at 8:26 PM Jim via Gmclist
wrote:

> I did read back through some posts concerning the subject, even before I
> started the operation. I was getting the impression it was the diameter of
> the mounting stem and not the length that was causing issues, perhaps I
> misunderstood.
>
> Diameter on both filter stems is exactly the same.
>
> I had a fellow GMCer that is ready to do the same maintenance on his coach
> check out the specs on his filter, his being a Wix and this is a Power
> Torque with part number FK-117. His Wix specs came back identical to this
> unit.
>
> This unit was acquired in the USA and not here in The Great White North...
>
> It's a mystery...
> --
> Jim Owens,
>
> 78 Royale,
>
> Out skirts of Kitchener, Ontario
>
> _______________________________________________
> GMCnet mailing list
> Unsubscribe or Change List Options:
> http://list.gmcnet.org/mailman/listinfo/gmclist_list.gmcnet.org
>
 
Rich, Posting confusing messages is my specialty I'm afraid.

It is perhaps OCD but when one sets out to do a simple operation such as removing a filter and pushing a new one back into its place. One would hope
it would be as simple as that.

You may be on to something on the new filter a bit out of round. It doesn't appear to be but it may have a slightly built up edge that is not allowing
it to full seat.

I have jacked the coach up a couple inches higher so I can have a better look. It was a bit tight under there. It was high enough to complete the job
if everything went smooth. Not quite high enough to start monkeying around.

I guess the best way to describe the situation is the existing filter seats snuggly into place and stays in place. It is not effected by gravity
pulling it out of place. The new one doesn't want to seat securely. I'm sure if I took my finger off it, it would fall out.

I was talking with another GMCer and they were under the impression that the pan holds the filter in place. The filter I removed is staying in place
without the pan.

--
Jim Owens,

78 Royale,

Out skirts of Kitchener, Ontario
 
I just did mine a month ago and the ATP filter I got was the right size. I used two O-rings on it and did not have any problems. The outlet that
goes up into the transmission body needs to measure 3/4" in diameter
--
Carl Stouffer
'75 ex Palm Beach
Tucson, AZ.
Chuck Aulgur Reaction Arm Disc Brakes, Quadrabags, 3.70 LSD final drive, Lenzi knuckles/hubs, Dodge Truck 16" X 8" front wheels, Rear American Eagles,
Solar battery charging. GMCSJ and GMCMI member
 
You ABSOLUTELY, POSITIVELY, do not want the transmission replacement filter
to be even a tiny bit loose in the valve body bore. If it sucks air, you
will soon have an expensive transmission to repair. Been there, done that.
Serious no-no. The oil pan should not be the thing that holds that filter
in place. Friction fit in the bore is. Two "0" rings? If it makes you feel
better, O.K.
Jim Hupy
Salem, Oregon

On Mon, Mar 30, 2020, 8:27 AM Carl Stouffer via Gmclist <

> I just did mine a month ago and the ATP filter I got was the right size.
> I used two O-rings on it and did not have any problems. The outlet that
> goes up into the transmission body needs to measure 3/4" in diameter
> --
> Carl Stouffer
> '75 ex Palm Beach
> Tucson, AZ.
> Chuck Aulgur Reaction Arm Disc Brakes, Quadrabags, 3.70 LSD final drive,
> Lenzi knuckles/hubs, Dodge Truck 16" X 8" front wheels, Rear American
> Eagles,
> Solar battery charging. GMCSJ and GMCMI member
>
> _______________________________________________
> GMCnet mailing list
> Unsubscribe or Change List Options:
> http://list.gmcnet.org/mailman/listinfo/gmclist_list.gmcnet.org
>
 
On Mon, Mar 30, 2020 at 8:38 AM James Hupy via Gmclist <

> You ABSOLUTELY, POSITIVELY, do not want the transmission replacement filter
> to be even a tiny bit loose in the valve body bore. If it sucks air, you
> will soon have an expensive transmission to repair. Been there, done that.
> Serious no-no. The oil pan should not be the thing that holds that filter
> in place. Friction fit in the bore is. Two "0" rings? If it makes you feel
> better, O.K.
> Jim Hupy
> Salem, Oregon
>
> On Mon, Mar 30, 2020, 8:27 AM Carl Stouffer via Gmclist <

>
> > I just did mine a month ago and the ATP filter I got was the right size.
> > I used two O-rings on it and did not have any problems. The outlet that
> > goes up into the transmission body needs to measure 3/4" in diameter
> > --
> > Carl Stouffer
> > '75 ex Palm Beach
> > Tucson, AZ.
> > Chuck Aulgur Reaction Arm Disc Brakes, Quadrabags, 3.70 LSD final drive,
> > Lenzi knuckles/hubs, Dodge Truck 16" X 8" front wheels, Rear American
> > Eagles,
> > Solar battery charging. GMCSJ and GMCMI member
> >
> > _______________________________________________
> > GMCnet mailing list
> > Unsubscribe or Change List Options:
> > http://list.gmcnet.org/mailman/listinfo/gmclist_list.gmcnet.org
> >
> _______________________________________________
> 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
 
All I know is that the filters come from one source, so brand does not
matter.
Suggest you mark how far the original went up and make sure the new does
the same.

On Mon, Mar 30, 2020 at 8:38 AM James Hupy via Gmclist <

> You ABSOLUTELY, POSITIVELY, do not want the transmission replacement filter
> to be even a tiny bit loose in the valve body bore. If it sucks air, you
> will soon have an expensive transmission to repair. Been there, done that.
> Serious no-no. The oil pan should not be the thing that holds that filter
> in place. Friction fit in the bore is. Two "0" rings? If it makes you feel
> better, O.K.
> Jim Hupy
> Salem, Oregon
>
> On Mon, Mar 30, 2020, 8:27 AM Carl Stouffer via Gmclist <

>
> > I just did mine a month ago and the ATP filter I got was the right size.
> > I used two O-rings on it and did not have any problems. The outlet that
> > goes up into the transmission body needs to measure 3/4" in diameter
> > --
> > Carl Stouffer
> > '75 ex Palm Beach
> > Tucson, AZ.
> > Chuck Aulgur Reaction Arm Disc Brakes, Quadrabags, 3.70 LSD final drive,
> > Lenzi knuckles/hubs, Dodge Truck 16" X 8" front wheels, Rear American
> > Eagles,
> > Solar battery charging. GMCSJ and GMCMI member
> >
> > _______________________________________________
> > GMCnet mailing list
> > Unsubscribe or Change List Options:
> > http://list.gmcnet.org/mailman/listinfo/gmclist_list.gmcnet.org
> >
> _______________________________________________
> 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
 
Jim,
In addition to using two o-rings, also make sure that the lower portion of the filter is lined up properly or else you will not be able to fully
insert it. I had that problem. It will be easier to see if you jack the coach up higher.

http://www.gmcmhphotos.com/photos/spring-maintenance-2019/p67145-transmission-filter-fit.html

Once lined up, it went all the way in.

http://www.gmcmhphotos.com/photos/spring-maintenance-2019/p67148-transmission-filter-fit.html

I hope this helps.
Russell
--
Russell Keith,
1978 E2 "Harry" 403 (still carbureted), Danny Dunn Tranny, Thorley, Stock Brakes w/Remote Vacuum Brake Booster, Quad Bags, Dakota Digital Dash, 6.5 kW
Onan, Dunedin, Florida
 
Thanks to everyone that responded. The new filter is in place nice and secure.

I raised the coach a bit higher so I could have a better understanding of the situation.

Both filters have the exact same diameter throughout the length that inserts into the the trans.

I had to square the new one exactly and tap it in with a mallet. I tapped it on the reinforced edge. Once I had it started it pushed right up in with
taps of mallet. It's not going anywhere.

I misunderstood how far the filter went into the slot...


--
Jim Owens,

78 Royale,

Out skirts of Kitchener, Ontario
 
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