Transmission oil help

[Dominiqueb]

Fleetwood Flair 30H
Workhorse chassis 2000 P32
454 GM 7.4L ??

My MH has only 37k miles and I presume the transmission oil never been changed but the oil level is low
with engine running warm it's showing the lower tread level with darker red color. My questions is:

In which year GM start to use synthetic oil for transmission.

Should I change oil and filter or just added one quart .

What kind of oil I should use to change or ad , synthetic or mineral.

Transmission shifts very well but the radiator gets very hot. 200F??
It can be normal??

My mechanic tell me to change the oil using synthetic and don't worry about it.

Expert's transmission shops tells me don't change anything, just add a quarter of oil, new oil detergente is going to dissolve particles and clog your transmission.

I'm really don't know what to do and I don't want to damage a transmission it's working fine.

Please let me know your opinion I want to get the road soon!

Thanks for your help!!!
.

[MrMark52]

Don’t fix what isn’t broken - add the needed amount of fluid and drive.

Note that typically, the distance between the marks on a transmission dip stick is 1 pint, not 1 quart.

We had a ‘91 P30 454 just as you describe, got it in ‘18 with 17k miles on it. When we sold her Jan ‘21, she had 27k miles on her. Drove most of those miles pulling a Jeep Wrangler from Dallas to Westcliffe, CO, from there to 4 corners and Carlsbad - not to forget a few trips Dallas to the hill country of Texas.

All I did to any of the fluids was change the oil/filter, replaced the 3 rubber hydraulic brake lines (2 front disc, 1 rear for the drum brakes). I did have to pull the radiator and have recored - the 3 PO’s didn’t properly maintain the coolant system so the radiator sprung a leak - which meant a full flush and changeout of the coolant system.

My Jeep Wrangler consistently runs right around 210 degrees based on the dash garage. Our current coach has the 8.1l engine and is pretty consistent at around 195-200 degrees.

I’m not sure if temperature data can be read at the OBDII port on your coach but it wouldn’t hurt you to get a scanner any way to look at what data you can get from that port. I use a FoxWell N301 as you can record live data for later evaluation of engine performance.

[Dominiqueb]

Great answer thank you!!!
But what kind of oil I should add it
Mineral or synthetic, I just like to have the full specification of the oil I should use.

[MrMark52]

If I remember correctly, it’s Dexron II. Look on the dipstick, I think it tells you.

If not, find the chassis or service manuals.

There is a general P30 Motorhome chassis manual/guide that Chevrolet produced that will be of great help to you as it applies to all chassis related issues on the P-Series chassis used under MoHo’s.

FWIW - in all likelihood, the driver side bell crank on your coach is worn out. Mine was at 17k miles when we got the coach, amongst several other steering linkage components.
I ended up replacing the drive side bell crank, pitman arm, tie rod, and all the tie rod ends on our coach.
It went from tracking all over the road and beating me up like I was riding a bull to single handed driving in 1 lane.

[SteveJ.]

The recommendation from GM is to use a Dexron VI that has a GM approval.

This is a synthetic fluid that will mix with your current fluid(assuming it is factory fill).

What I do is drain the trans oil pan every other engine oil change (using the drain plug) and about every 25-30k miles actually drop the pan and change the filter.

The pan gasket should be a reusable one.

This particular drive train does have issues with building trans heat. Do get a trans temp gauge if you drive in hills/mountains, especially if pulling a trailer or toad.

The newer DexronVI is more stable with higher temps but who knows about the older trans internal seals and such.

Edit to add: When checking the trans fluid level make sure that the fluid is at normal temp. Just warming up the engine to temp by idling it is not going to get the tranny hot enough, check it after driving it for a while.

[George Schweikle]

My previous MH was a '99 with 454 & GM transmission. The GM dashboard temperature gauge is known to be very inaccurate so I used a scangauge to read both engine and tranny temperature.

Originally Posted by MrMark52

....I’m not sure if temperature data can be read at the OBDII port on your coach but it wouldn’t hurt you to get a scanner any way to look at what data you can get from that port. I use a FoxWell N301 as you can record live data for later evaluation of engine performance.

[GypsyR]

Your transmission will be a "4L80E" and is considered rather "old school" these days. I would treat it as such. Around in the thirty thousand mile range is the perfect time for a transmission service. Such a service means a transmission shop will remove the pan, INSPECT it for excessive debris, clean it, and replace the filter. If the person doing this sees something in the pan they don't like, they might cut open the old filter for inspection too. It would be perfectly normal for your particular transmission to have a shadow of what looks like black dust stuck on the pan itself under the fluid. That's fine. Not fine would be a layer of sludge or metallic particles.
Without such a service you won't have a professional estimate of how well your transmission is faring and/or won't be apprised of any warning signs.

Originally your transmission used Dexron III/Mercon. In YOUR transmission you will want to update to a refill with Dexron VI. It is a full synthetic that will happily mix with what is in there now. GM specifies doing this. Such a fluid change only replaces part of your fluid and that's fine too. Fluid ages quite well, it's the additives in it that break down. Detergents, friction modifiers, and such. The addition of the fresh six to eight quarts the above type change freshens up those additives quite well enough to go another 30-40 thousand miles easily.

There is a phenomenon where very old and abused fluid can be a problem if changed. I have seen it. The fluid will be actually a dark brownish color and smell like what people call "lacquered". IE, it stinks. Yours is dark red and low mileage so it doesn't apply but it's a thing. Nasty fluid is replaced with fresh and within a week the fresh detergents knocked something loose that was hanging by a thread. Every transmission shop that has been in business for more than a few years has seen this. And been blamed.

This is some very specific info I have given, for YOUR specific year and model coach. A slightly newer version of the same coach will have an Allison transmission which does NOT like Dexron VI. It is well know to cause problems. But the later Allisons were redesigned and like Dexron VI just fine. Many a Toyota and Honda is happily running up toe 300 thousand miles with some awful looking dark brown transmission fluid. Those just turn their fluid brown and it doesn't matter. A large number of apples and oranges here, general advice doesn't quite cut it.

[Dominiqueb]

Thank you, I truly appreciate you share your knowledge with us, since I believe you know what you're doing I have a question: why use Dex VI when that transmission it is design for Dex III, my question is: a high-tech detergents in
(Dex VI) can dissolve deposits and then they can float all over clogging the transmission.
I'm sure you done this before couple times and I'm planning to follow your advice.
Can you please suggest a brand oil you trust.
Should I keep the same seal, some comments say it's better but I don't know anything about it.
Do you know what is the right torque I'm making sure equal pressure in all Bolts.

Since I have a a drain plug I'm planning to warm the old oil and drain, question? After that it will hurt anything do I do the engine for 30 seconds to pump more oil through the drain plug in this way drain more oil as possible?

Thanks a lot have a wonderful day!

[MrMark52]

No! Never!

The pump won’t pump more oil thru the engine because there is nothing for the pump to pick up to push the remaining oil they.

The pump isn’t a suction pump, it’s a pressure pump.

Not to mention that there isn’t enough residual oil in the engine to prevent dry bearing damage.

If you want the cleanest oil possible in the engine (meaning getting the old oil out), change the oil, run the engine til warm again, then change the oil again. You’ll have better than 95% of the old oil out of the engine.

Transmissions are a whole ‘nether story.

[Dan_Frisbie]

I’ve had 2 4L80 transmissions in trucks and never had a problem with either because every 30,000 miles or so I had them flushed.
A flush is a complete fluid exchange and is the best way to preserve your transmission and keep it alive for a long time.
Changing the filter and refilling it at home changes about half of the fluid.
200 degrees in the radiator will keep the tranny in a good operating range.

These are very good, very strong, and very reliable transmissions if you keep them clean and cool.

[Dominiqueb]

Originally Posted by GypsyR

Your transmission will be a "4L80E" and is considered rather "old school" these days. I would treat it as such. Around in the thirty thousand mile range is the perfect time for a transmission service. Such a service means a transmission shop will remove the pan, INSPECT it for excessive debris, clean it, and replace the filter. If the person doing this sees something in the pan they don't like, they might cut open the old filter for inspection too. It would be perfectly normal for your particular transmission to have a shadow of what looks like black dust stuck on the pan itself under the fluid. That's fine. Not fine would be a layer of sludge or metallic particles.
Without such a service you won't have a professional estimate of how well your transmission is faring and/or won't be apprised of any warning signs.

Originally your transmission used Dexron III/Mercon. In YOUR transmission you will want to update to a refill with Dexron VI. It is a full synthetic that will happily mix with what is in there now. GM specifies doing this. Such a fluid change only replaces part of your fluid and that's fine too. Fluid ages quite well, it's the additives in it that break down. Detergents, friction modifiers, and such. The addition of the fresh six to eight quarts the above type change freshens up those additives quite well enough to go another 30-40 thousand miles easily.

There is a phenomenon where very old and abused fluid can be a problem if changed. I have seen it. The fluid will be actually a dark brownish color and smell like what people call "lacquered". IE, it stinks. Yours is dark red and low mileage so it doesn't apply but it's a thing. Nasty fluid is replaced with fresh and within a week the fresh detergents knocked something loose that was hanging by a thread. Every transmission shop that has been in business for more than a few years has seen this. And been blamed.

This is some very specific info I have given, for YOUR specific year and model coach. A slightly newer version of the same coach will have an Allison transmission which does NOT like Dexron VI. It is well know to cause problems. But the later Allisons were redesigned and like Dexron VI just fine. Many a Toyota and Honda is happily running up toe 300 thousand miles with some awful looking dark brown transmission fluid. Those just turn their fluid brown and it doesn't matter. A large number of apples and oranges here, general advice doesn't quite cut it.

Thank you, I truly appreciate you share your knowledge with us, since I believe you know what you're doing I have a question: why use Dex VI when that transmission it is design for Dex III, my question is: a high-tech detergents in
(Dex VI) can dissolve deposits and then they can float all over clogging the transmission.
I'm sure you done this before couple times and I'm planning to follow your advice.
Can you please suggest a brand oil you trust.
Should I keep the same seal, some comments say it's better but I don't know anything about it.
Do you know what is the right torque I'm making sure equal pressure in all Bolts.

Since I have a a drain plug I'm planning to warm the old oil and drain, question? After that it will hurt anything do I do the engine for 30 seconds to pump more oil through the drain plug in this way drain more oil as possible?

Thanks a lot have a wonderful day!

[GypsyR]

OK. Dexron VI is specified by General Motors, not me. In the majority of their transmissions they say to use VI instead of III. In fact they stopped licensing people to make III, in effect saying "don't make this any more". That's me talking here, but with a bit of searching no doubt you could find the official "TSB's" from GM talking about all this. TSB's are bulletins sent out from the main company to dealerships and such to advise them of revised service procedures, problems, fixes, etc the GM engineers have figured out.

VI and III have the same detergents. VI is a lower viscosity oil, meaning it's a bit thinner and more fuel efficient. Also a synthetic oil formula where III is not. So basically a fairly simple upgrade. I don't care who makes it, if it clearly says Dexron VI on the front label, it's licensed by GM and will be the good stuff. Brand doesn't matter at all like it can for motor oil and other things.

No need to warm the transmission before changing. It's always best to change engine oil "hot" but that doesn't apply to transmissions. If it's cold outside and you'd prefer working on a warm transmission, that's up to you. Warm it if you want, it doesn't matter.

If you have a torque wrench that reads that low, pan bolt torque is nine ft/lbs. I'd like to say I torque them but I don't. 40 year of mechanic's "feel" works OK for me. The rubber and metal reusable gaskets are the best and very tolerant of torque mistakes and generally don't need to be retorqued. They are listed as "bonded rubber" and are not very cheap nor widely available. You can order them online from places like Summit Racing for $25 or so.
The traditional cork ones are not good about retaining torque and I've had to retighten their bolts up to three times before I was happy. Check again after 500 miles and they'll need retightening again. There are also flimsy plain rubber ones that come with most parts store "filter kits". I don't like them much but they work. They usually need to be rechecked or retightened once and so kind of outperform cork. Unlike cork, if you plan to do another change in 500 or 1000 miles or so very often you can reuse one of them Once.
Transmission shops often use "paper" or "fiber" gaskets. I like these. Cheaper than the bonded ones and generally after the first check don't need to be retightened and perform almost as well. You don't really see them for sale at local parts stores though. Generally it's a really good idea to recheck your bolts after 500 miles no matter what though.

Rule of thumb is to never run the engine when there is no fluid in the transmission. Many a transmission has been damaged by being driven with not enough fluid in it. Though most likely you wouldn't hurt anything by doing as you suggested as it would just be sitting and idling neither is it a good idea. What you said sort of kind of works on completely different transmissions just FYI, but doesn't apply to this one. Just drain it, change the filter, and refill it.

I don't care for flushes as it leaves completely out anyone doing any kind of inspection at all. Nor do I believe a regularly serviced transmission needs ALL it's fluid changed. That's just me.

[paulwang]

I have the same MH, similar mileage

200F should be normal and good.

I change transmission fluid with Dexron III and replace a new oil filter. The original metal gasket is reusable and better than the one I bought from Amazon, so I used the old one.

I didn't flush the transmission, but I changed the fluid in 2020 without taking off the oil pane, just drain the oil from drain hole. Last year, I took off the pane and replace the filter.

Don't have any complain after drove 5000+ km.

[Charles L]

I agree that you should use the newer fluid recommended by GM. I think a new filter is a no brainer for an RV as old as yours. I am not sure what is inside the filter. Perhaps it is just a fine mesh screen. I would just replace it and have a new gasket on hand. You can return it if you do not need it. Now all this could cost $110.00 in parts and fluid. If money is tight just drain and fill for $60.00. I tend to go overboard on my mechanical maintenance.