Cooked my tranny

LQQKatJon

LQQKatJon

Well-known member
Oct 22, 2010
3,216
534
113
St. Cloud, Mn
lqqkatjon.blogspot.com
Trying to work out a tow in wyoming.

I was driving back from oregon. Went through yellowstone.

And it did not make it to the top of hwy 16 between 10 sleeps and buffalo, wy.

Downshifting at 45-50mph. Trying to hold speed. (Usually 30-40mph).

I have a 2018 fall rebuilt tranny. 455. With ebl efi. Engine seems ok.

Tranny is hooked up to radiator, then to an external tranny cooler. Running mobil 1.

I am towing 3500 pound crv. And have 3.21 gearing.

When heading over passes westbound. Things seemed well. The engine/tranny seemed to pull the grades fine and hold 40-45mph at 2800-2900 rpm.
Maybe 2/3 to 3/4 throttle.

Heading back east it seemed to struggle more and more. (Hills seemed longer.). The one the coach quit moving on was really long. 10 miles??

Think i am pushing it or had some issue with rebuild? I dont know how to take it much easier. Not like I want to pull over facing uphill and
try yo het going again? And those spots are few and far between???

Just wondering experience and thoughts.
--
Jon Roche
75 palm beach
EBL EFI, manny headers, Micro Level, rebuilt most of coach now.
St. Cloud, MN
http://lqqkatjon.blogspot.com/
 
Jon,

You've got me concerned. I'm driving that same route in September. I have driven up I-17 from Phoenix to Flagstaff several times and there are some
long steep grades along that route. In fact I will be heading up that way next weekend. I have never had a problem. No tranny temp gauge, but maybe
I should add one quick between now and then.
--
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
 
Carl S.:
I highly recommend a tyranny temp gauge or a Digipanel (reads 4 or 5 important items) and you can set it to alarm if one of them gets excessive (available from Jim K. at Applied GMC).
Trans temp gauge saved my bacon about 5 years ago when I was in steep inclines on way from El Paso w/ a 65 Corvair in tow. Noticed temp gauge getting pretty hot and getting to far edge of gauge. Found a place to pull off hiway, let it cool for 1/2 hr, then proceeded on my way - no damage but came close to being dizzyastris - just sayin!
Still driving same tranny.
Mike/The Corvair a holic

Sent from my iPhone

>
> Jon,
>
> You've got me concerned. I'm driving that same route in September. I have driven up I-17 from Phoenix to Flagstaff several times and there are some
> long steep grades along that route. In fact I will be heading up that way next weekend. I have never had a problem. No tranny temp gauge, but maybe
> I should add one quick between now and then.
> --
> 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
 
Does the tranny fluid smell burnt? Is it still the origanl color or is it brownish now?

--
Rich Mondor,

Brockville, ON

77 Hughes 2600
 
Looks pink.

My nose is not super. I have seen burnt fluid that is obvious. This is not obvious.

Mobil 1 synthetic. I have never had that in a tranny before this one so I am not super familiar with what it looks like when it’s Burnt.
--
Jon Roche
75 palm beach
EBL EFI, manny headers, Micro Level, rebuilt most of coach now.
St. Cloud, MN
http://lqqkatjon.blogspot.com/
 
Hmmmm i know that in my road race bikes synthetic fluid and clutches didnt really like each other...not sure about this case. Its may be to late but
you could try dropping the fluid and putting in regular ATF....nothing to loose, all to gain.

> Looks pink.
>
> My nose is not super. I have seen burnt fluid that is obvious. This is not obvious.
>
> Mobil 1 synthetic. I have never had that in a tranny before this one so I am not super familiar with what it looks like when it’s Burnt.

--
Rich Mondor,

Brockville, ON

77 Hughes 2600
 
I’ve never used synthetic fluid, probably just in my head but I don’t want to use anything that in theory is slipperier than what the trans was
designed for. It gives a few added degrees of temp range before cooking, but then that also subjects the trans to those high temps. I try to not go
into those temp extremes. Whose rebuild? I know the 3.21 is The Deal, but towing and mountains may point to 3.55-3.73 as a better combo. Hope you
get sorted soon.
--
John Lebetski
Woodstock, IL
77 Eleganza II
 
The builder I use was out of South Dakota he had done your GMC motor on transmissions that I am aware of and they have not had any issues. I haven’t
had a chance to talk to him yet. Space he is the one that recommended that I use the mobile one synthetic I am usually not a synthetic person. I
question the torque converter because they’re always was something a little bit on on how it took off from a stop
--
Jon Roche
75 palm beach
EBL EFI, manny headers, Micro Level, rebuilt most of coach now.
St. Cloud, MN
http://lqqkatjon.blogspot.com/
 
Synthetic fluid served me well in the mountains I believe Manny suggests Mobil one in his switch pitch rebuilds. You really got to know your trans
temperatures on hard mountain climbs . Towing a CRV on long mountain grades would be a lot easier on the engine and tranny with a 3:73 final then the
3:21 in the mountains I’ve done both but my toad was 900 lbs lighter then yours. If you only have your throttle at 3/4 peddle you shouldn’t be
over working the unit though in 2nd I presume. When I was running a 3:21 a lot of those grades would have been a hair raising pull in 1st gear at the
summit.
--
Roy Keen
Minden,NV
76 X Glenbrook
 
I run AMSOIL synthetic ATF and it has served me well. You will cook the seals and soft parts before damaging the synthetic ATF. I have the power
drive gearing and towd an HHR over the same route. We had to unhook and drive independently in the summer.

I agree with the previous posters about trans oil temp gauge and the need for taller gearing.
--
1977 Eleganza II
Ogden NY
 
Well, I have a Manny Transmission in my 78 Royale, along with a 3:70 - 1
final drive ratio. He recommended that I use synthetic transmission fluid.
I started out with Valvoline Synthetic, ran it for a couple of thousand
miles, then drained it as much as I could. I replaced the stock oil pan
with a finned aluminum Ragusa pan that I coated with glyptal and cured in
the powder coat oven in my shop. Would not recommend using the oven in your
kitchen. Serious bitching will occur if you are married and she catches you
doing it.
I then refilled with Valvoline Synthetic ATF and added a temperature
sending unit to it and the final drive at the same time. I drove it a
couple of years before I bothered wiring up the gages, fat, dumb, ignorant,
and happy. Then, I hooked up the gages. The transmission gage registers
160° constantly at the oil pan. Only moves off thet number through the
Siskiyou's on Interstate 5, that has several long climb 6% grades, but only
10° or so. The combination of the in-radiator plus the additional liquid to
air B & M multi finned auxiliary cooler plus the finned aluminum pan keeps
it cool. No.concerns. The final drive? Another matter indeed. Only 2 quarts
of gear oil in there. And lots of heavy loading. That computes to 250°
running down the flat n level, Approaches 300° with any hill climbing. I
use Synthetic Gear Oil in it, and those temps concern me a bit. Been that
way for years, though. No failures yet. Before the gages were hooked up,
never thought about it much. Guess all the gages achieved were to give me
something else to worry about driving down the road! Ah, such is life, I
guess.
Jim Hupy
Salem, Oregon

On Sun, Jul 12, 2020, 10:54 AM Ernest Dankert via Gmclist <

> I run AMSOIL synthetic ATF and it has served me well. You will cook the
> seals and soft parts before damaging the synthetic ATF. I have the power
> drive gearing and towd an HHR over the same route. We had to unhook and
> drive independently in the summer.
>
> I agree with the previous posters about trans oil temp gauge and the need
> for taller gearing.
> --
> 1977 Eleganza II
> Ogden NY
>
> _______________________________________________
> GMCnet mailing list
> Unsubscribe or Change List Options:
> http://list.gmcnet.org/mailman/listinfo/gmclist_list.gmcnet.org
>
 
I put whatever Manny says I should put in one of HIS trannys.

Sully
Bellevue wa

On Sun, Jul 12, 2020 at 11:23 AM James Hupy via Gmclist <

> Well, I have a Manny Transmission in my 78 Royale, along with a 3:70 - 1
> final drive ratio. He recommended that I use synthetic transmission fluid.
> I started out with Valvoline Synthetic, ran it for a couple of thousand
> miles, then drained it as much as I could. I replaced the stock oil pan
> with a finned aluminum Ragusa pan that I coated with glyptal and cured in
> the powder coat oven in my shop. Would not recommend using the oven in your
> kitchen. Serious bitching will occur if you are married and she catches you
> doing it.
> I then refilled with Valvoline Synthetic ATF and added a temperature
> sending unit to it and the final drive at the same time. I drove it a
> couple of years before I bothered wiring up the gages, fat, dumb, ignorant,
> and happy. Then, I hooked up the gages. The transmission gage registers
> 160° constantly at the oil pan. Only moves off thet number through the
> Siskiyou's on Interstate 5, that has several long climb 6% grades, but only
> 10° or so. The combination of the in-radiator plus the additional liquid to
> air B & M multi finned auxiliary cooler plus the finned aluminum pan keeps
> it cool. No.concerns. The final drive? Another matter indeed. Only 2 quarts
> of gear oil in there. And lots of heavy loading. That computes to 250°
> running down the flat n level, Approaches 300° with any hill climbing. I
> use Synthetic Gear Oil in it, and those temps concern me a bit. Been that
> way for years, though. No failures yet. Before the gages were hooked up,
> never thought about it much. Guess all the gages achieved were to give me
> something else to worry about driving down the road! Ah, such is life, I
> guess.
> Jim Hupy
> Salem, Oregon
>
> On Sun, Jul 12, 2020, 10:54 AM Ernest Dankert via Gmclist <

>
> > I run AMSOIL synthetic ATF and it has served me well. You will cook the
> > seals and soft parts before damaging the synthetic ATF. I have the power
> > drive gearing and towd an HHR over the same route. We had to unhook and
> > drive independently in the summer.
> >
> > I agree with the previous posters about trans oil temp gauge and the need
> > for taller gearing.
> > --
> > 1977 Eleganza II
> > Ogden NY
> >
> > _______________________________________________
> > 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 Hupy wrote, " Before the gages were hooked up,
never thought about it much. Guess all the gages achieved were to give me
something else to worry about driving down the road!"

I guess I kind of feel the same way as Jim about the issue of additional gauges. It's not that what you don't know can't hurt you, it sometimes can.

I remember back in June of 1973, the day after I graduated from high school, my parents and I moved back to Tucson after living in Lebanon, PA for
five years. My dad was driving the family station wagon, a '70(?) Dodge Polara with a 383 and a 727 automatic transmission. We were flat towing my
'53 CJ-3B Jeep, plus a full load of luggage etc. across the country.

When we got into New Mexico, on route 70, and started climbing mountains, my dad became concerned with the transmission temperature, even without a
temp gauge on the transmission. He said the transmission heat was transferring to the engine and the cooling system was having a hard time shedding
the extra heat. He opted to take a break and make the rest of the trip at night.

I've remembered that all these years and I'm thinking the same applies with the GMC. Maybe the configuration of the front wheel drive transmission
doesn't transfer the heat the same as a rear wheel drive set-up does, but I think the same principle applies.

I drive in mountainous terrain quite often and always keep a close eye on my stock gauges, and have never seen my temperature gauge raise much at all
on long steep climbs, even in near or over 100 degree outside temps.

Still, I think a transmission temperature gauge is definitely in my future.
--
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
 
In this case my engine temp was never above 203 degrees.

I have seen some hot engines when climbing grades. And have pulled over years ago to let a car of mine cool down. That day it was by bozeman, mt
and 90 some degrees outside at noon.

The gmc engine since i have the new motor and aluminum radiator. Sits at 198 most of time. I have seen maybe 205 in the past year. It is
always steady temps.
--
Jon Roche
75 palm beach
EBL EFI, manny headers, Micro Level, rebuilt most of coach now.
St. Cloud, MN
http://lqqkatjon.blogspot.com/
 
Jon do you have motion now that your trans has cooled off or is it still the same?

Do you have any gears at all? As its strange you dont have something.

Like i said, if your kinda stuck i would put conventional ATF in it and see what happens....from there you could add some "tranny magic" in a bottle
to see what happens (what have you got to loose?)....short of getting a presure test done i dont think there is much you can do.

Stupid question for the masses....what if he lost the governer gear, would that have the same symptons? Im still hung on the "no drive" part as you
usually have something.
--
Rich Mondor,

Brockville, ON

77 Hughes 2600
 
Rich M.:
When I had the trans problem w/ my 23’ GMC, I had pulled in and parked for breakfast. When I came out, it would not move (in any gear). My mechanic (I am not one) said go to Walmart, buy a bottle of “Trans X”, pour 1/2 in, start engine, try all gears, if does not move wait 10 mins and try again, keep doing it, may or may not solve your problem but worth a try.
It worked after 3rd try (1/2 hr) so I drove it carefully to a nearby large empty car lot and then tried it in every gear. Seemed to be working fine so I drove gently (no heavy throttle and not over 55 mph) for 245 miles to get home. Mechanic checked it next day and said it seems to be fine. Drove it for another year w/ no problems.
I carry a bottle of “Trans X” w/ me in all my GMC’s - had 5 now down to 3.
Mike/the Corvair a holic

Sent from my iPhone

>
> Jon do you have motion now that your trans has cooled off or is it still the same?
>
> Do you have any gears at all? As its strange you dont have something.
>
> Like i said, if your kinda stuck i would put conventional ATF in it and see what happens....from there you could add some "tranny magic" in a bottle
> to see what happens (what have you got to loose?)....short of getting a presure test done i dont think there is much you can do.
>
> Stupid question for the masses....what if he lost the governer gear, would that have the same symptons? Im still hung on the "no drive" part as you
> usually have something.
> --
> Rich Mondor,
>
> Brockville, ON
>
> 77 Hughes 2600
>
> _______________________________________________
> GMCnet mailing list
> Unsubscribe or Change List Options:
> http://list.gmcnet.org/mailman/listinfo/gmclist_list.gmcnet.org
 
If I read this right, you lost trans power where it just stopped moving you forward. Trans fluid is pink and does not smell burned. I'm not a trans
expert by any means, but sounds like something in the trans broke. It will be interesting to see what the post mortem reveals. I'd bet is is
something simple. JWIT
--
Larry
78 Royale w/500 Caddy
Menomonie, WI.
 
... The final drive? Another matter indeed. Only 2 quarts
of gear oil in there. And lots of heavy loading. That computes to 250?
running down the flat n level, Approaches 300? with any hill climbing. I
use Synthetic Gear Oil in it, and those temps concern me a bit. Been that
way for years, though. No failures yet. Before the gages were hooked up,
never thought about it much. Guess all the gages achieved were to give me
something else to worry about driving down the road! Ah, such is life, I
guess.
Jim Hupy
Salem, Oregon
 
I was one of the people that Mike Kelly called. And told Mike about the Trans X trick. Maybe others also said the same thing. It softens hardened lip seals on the clutch pack. It will NOT fix the trans. For $6. Worth a shot. If your trans hasn't been rebuilt. Then Trans X is a must to have along.
Bob Dunahugh
 
Bob D.:
Thanks Sir - for your original recommendation and your follow thru here.
As you know I just had the trans on my 1st GMC rebuilt - no “Trans X” fix this time. Tx. mechanic found metal parts (not shavings) in pan at time of fluids change.
I Used Eagle transmissions out of Cedar Park, Tx. because of his experience w/ our GMC TH 425 tranny’s and recommendations from Tx. GMCers. 4 days of actual work and 2 1/2 wks waiting on parts out of New Jersey. Eagle trans is a nationwide company w/ sites in many major U S cities - not sure they all have experience w/ our trannies but could be worth a call if ever in need.
Just want all GMCers to have info at hand if they should have the need.
All hail our GMC community!!!
Mike/the Corvair a holic

Sent from my iPhone

>
> I was one of the people that Mike Kelly called. And told Mike about the Trans X trick. Maybe others also said the same thing. It softens hardened lip seals on the clutch pack. It will NOT fix the trans. For $6. Worth a shot. If your trans hasn't been rebuilt. Then Trans X is a must to have along.
> Bob Dunahugh
> _______________________________________________
> GMCnet mailing list
> Unsubscribe or Change List Options:
> http://list.gmcnet.org/mailman/listinfo/gmclist_list.gmcnet.org
 
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