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440-T4 Transmission Fluid, Oil Pan, Pan Gasket, Filter


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BettyBuick
New User

Apr 10, 2017, 3:24 PM

Post #1 of 7 (252 views)
440-T4 Transmission Fluid, Oil Pan, Pan Gasket, Filter Sign In

Hello there:

If there are a couple of gurus out there, I’d really appreciate your advice, experience as I’ve not opened a transmission pan before. This car is basically my second car, and I’ve bought in to the tools and enjoy working on the Buick. My concerns/considerations follow here. Questions are at 3a, 3b, 4a. The transmission problems, recent repair work, is listed in the bottom three paragraphs.

My plan is to use a flat neoprene gasket, and change the filter and the accessible accumulators and whatever fluid comes out when the filter is changed. Then at the next motor oil change, I’ll change the fluid again and that will be the third partial change of fluid.

1) I’ve heard folks say changing all of the fluid in an old transmission could cause additional slippage and/or actual failure by removing dirt/friction from the trans fluid or by kicking up the dirt from the filter and elsewhere. I’ve also heard folks say not to worry about it and that changing the fluid will have no negative consequence. I’m planning to change the fluid and filter from the pan, no flush.

2) I’d like to change the trans filter as part of regular maintenance and because one third of the trans fluid was replaced a few months ago. I'll have to drop the oil pan, and if I’m not mistaken, removal of the pan provides access to a couple of accumulators. I plan to order a transgo kit and replace the accessible accumulators too. I'm hesitant to do this, the car is 27 years old and some folks say, "hey, if it ain't broke don't fix it!"

3) The oil pan has an unbroken ridge along the face of the pan rail. The rib goes around the bolt holes and according to the filter kit that I purchased, a neoprene gasket is needed for this type of pan with a ridge (19 bolt holes). I’ve located a flat neoprene gasket from Fel-Pro #TOS18668. I see the 4T60E and other transmissions sometimes use reusable neoprene gaskets with ridges -- these ridged gaskets seem to be a better match to this pan and are reusable but I can not locate one for the 440-T4.
a) Does anyone know where I can find a gasket that has the ridges and fits the 440-T4?
b) Would replacing the pan eliminate the ridge or does the existing ridge seat into a corresponding depression in the trans case?

4) I’m considering switching over to synthetic transmission oil. I’m guessing that change should be accomplished with a complete flush after I’ve gone through the process of slowly changing the traditional oil – unless there is no drawback to blending the oils in the case.
a) How would one transition to the synthetic trans fluid, would you recommend doing so?

Betty thanks you, and I thank you.

Some information about the transmission follows here
89,000 miles. 11qt capacity. About a year ago, I started hearing a clunk upon shifting into reverse. The clunk seems to happen less after startup as compared to after the car is warmed up and I’m parking it. Also, at lower speeds there will sometimes be a delay and a push/surge upon change of gears.

In September, after some service to the radiator, a slow leak in the trans cooling lines (rusted out) appeared and this caused the trans to be about a quart low on fluid. The lines were then replaced and at that time, 4 qts of trans fluid was replaced w/Castrol Dex VI. The filter was not replaced at that time. Then I installed a new vacuum modulator and then went and re-installed the original. The swapping of new and old vacuum modulators had no noticeable effect on the above issues. I adjusted the shift cable (push button adjuster) for an earlier shift and this has helped significantly with the shift thumping but has not eliminated the issue…I don’t like the feel of the new shift points but I’m hoping the earlier shifts will help preserve the trans a while (but my gut says it is doing the opposite) until I can get a better handle on the need for and cost of a refurb/rebuild.

The transmission seems about the same as before the 4qts were changed about 2000 miles ago -- maybe a little smoother…still occasionally thumping into gears at low speeds. It is possible that the trans fluid had never been changed before September…it was brown brown brown. (according to the maintenance manual the trans fluid should have been changed every 15,000 miles if the car was driven in city traffic where temps regularly exceed 90F). I’m in the city but the temp isn’t that bad except a couple months in the summer and there was lots of highway miles in there too. In any case, I am familiar with the car and do not recall ever asking for the trans fluid to be changed.

Thanks again!
1990 Buick LeSabre Sedan; 3.8L 3800; 440-T4


gsferraro
Enthusiast

Apr 11, 2017, 7:34 AM

Post #2 of 7 (221 views)
Re: 440-T4 Transmission Fluid, Oil Pan, Pan Gasket, Filter Sign In

Hello,
I will go down the line.

1- You shouldnt have an issue changing the fluid sounds like the condition is ok, if your fluid was like varnish then maybe leave it, but you should be ok.

2- As far as the accumulators go, they do wear out where the pin rides, but if you plan to take this down, there are gaskets that will tear so they will have to be replaced

3- If the pan has the rasied area then the neoprene gasket will have to be used, if the pan does not have a rasied area for the pan to seal and its just flat then the reusable gasket is used. If you use a reusable gasket on a pan that has the raised area, the pan will leak.

4- if you wanted to start using the synthetic oil, thats fine, wont hurt. you could drive the car drop the pan a few more times(no drain) to make the transition.

One more note on the filter, i would change the filter seal thats in the case, its like a metal clad seal that you have to knock in, i use a bushing driver.

What you may be feeling in reverse is a chatter on engagement, this is a fairly common issue and is addressed in the valvebody by cutting coils off a spring to raise pressure about 20 psi and replacing the reverse band.

I think thats it for now, any other questions just let me know. Gary(transmission shop owner)


BettyBuick
New User

May 19, 2017, 11:07 PM

Post #3 of 7 (65 views)
Re: 440-T4 Transmission Fluid, Oil Pan, Pan Gasket, Filter Sign In

Thank you, Gary. Your response is much appreciated.

I'm getting ready to order the supplies and i'm considering the type of fluid to use. The 1990 owner's manual says to use Dexron II. I'm leaning toward a Castrol product. Either Dexron VI, Dex/Merc, or High Mileage transmax. I read the product information and it seems like all three are compatible with my trans, or at least with Dexron II.

A few months ago, about four quarts of the old fluid was replaced with Dexron VI "synthetic blend". I plan to drop the pan once or twice more until the majority of the old fluid is out of the case and has been replaced with new Dexron VI. Then I want to begin incorporating the high mileage conventional fluid into the case as it includes additional cleaning agents. But, I feel like the idea of going from the synthetic blend to the conventional is somehow backwards or not recommended. Truly, I don't know which fluid is best for old Betty.

Would you care to comment or offer an opinion about these fluid considerations?

One more -- i'm planning to do each of the initial two changes after driving for at least 500 miles. Is there a recommended distance/break-in time between changes?

Thank you.

###
1990 Buick LeSabre Sedan; 3.8L 3800; 440-T4


BettyBuick
New User

May 19, 2017, 11:24 PM

Post #4 of 7 (59 views)
Re: 440-T4 Transmission Fluid, Oil Pan, Pan Gasket, Filter Sign In

I should ask if you have experience with using synthetic oils in transmissions as old as this one. Some folks say the synthetic could cause slippage...
1990 Buick LeSabre Sedan; 3.8L 3800; 440-T4


gsferraro
Enthusiast

May 20, 2017, 5:51 AM

Post #5 of 7 (48 views)
Re: 440-T4 Transmission Fluid, Oil Pan, Pan Gasket, Filter Sign In

Hello,
For your car, any of these fluids will work, castrol is a very good fluid, dex VI is too (how much is Dex VI per quart?, i dont really use that because i stock a full synthetic in my shop) I think the 500 miles is perfect for the fluid changes. Gary


BettyBuick
New User

May 20, 2017, 11:22 AM

Post #6 of 7 (37 views)
Re: 440-T4 Transmission Fluid, Oil Pan, Pan Gasket, Filter Sign In

Thanks.

it is $41 for six quarts at amazon prime which is just under $7/qt. I think there is a gallon option that brings the cost closer to $6

I think it is over $8/qt retail. That is practically twice the cost of some generic Dexron VI oils...noted.
1990 Buick LeSabre Sedan; 3.8L 3800; 440-T4


gsferraro
Enthusiast

May 22, 2017, 7:04 AM

Post #7 of 7 (22 views)
Re: 440-T4 Transmission Fluid, Oil Pan, Pan Gasket, Filter Sign In

Hello,
Sounds good, your going with the dex VI ? Gary






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