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Has anyone changed a 4T80E tranny?


Gene

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Yes i understand that this will be a BIG job. I am guessing that the transaxle assembly cradle (engine/tranny) would have to be dropped as a unit just to change the tranny. The reason for the removal is a bad trans axle pressure control solenoid. I have been told by a couple tranny shops that they would not chance just changing the trans axle pressure control solenoid. They claim that a piece of debris is what caused the failure and without totally cleaning and rebuilding the tranny it would fail again in a short time! I know that the shift solenoids get changed without a problem but they say that the trans axle pressure control solenoid is different! When the trans axle pressure control solenoid goes bad it lets the trans FLASH..run witout fluid and the clutch plates get destroyed/burnt.

Does anyone have any expirence with this problem or am i better off changinging the tranny? I have found a tranny at the boneyard for 400 bucks and it has 80K on it. The car is a 94 SLS 155K. What do you think?

Thanks

Gene

96 STS

93 ETC

66 ELDORADO

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Yes i understand that this will be a BIG job. I am guessing that the transaxle assembly cradle (engine/tranny) would have to be dropped as a unit just to change the tranny. The reason for the removal is a bad trans axle pressure control solenoid. I have been told by a couple tranny shops that they would not chance just changing the trans axle pressure control solenoid. They claim that a piece of debris is what caused the failure and without totally cleaning and rebuilding the tranny it would fail again in a short time! I know that the shift solenoids get changed without a problem but they say that the trans axle pressure control solenoid is different! When the trans axle pressure control solenoid goes bad it lets the trans FLASH..run witout fluid and the clutch plates get destroyed/burnt.

Does anyone have any expirence with this problem or am i better off changinging the tranny? I have found a tranny at the boneyard for 400 bucks and it has 80K on it. The car is a 94 SLS 155K. What do you think?

Thanks

Gene

96 STS

93 ETC

66 ELDORADO

Are you referring to the A & B shift solenoids? What codes are stored in diagnostics?

If you are referring to the A & B shift solenoids, the failure mode is a cracked mounting flange - nothing that would allow debris to spew into the trans... The solenoid kit is available for $70 and has a revised mounting bracket to prevent the new solenoid(s) from failing.

Search the archives - a few members have chainged their own solenoids.

Kevin
'93 Fleetwood Brougham
'05 Deville
'04 Deville
2013 Silverado Z71

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Hello KHE

The code is PO76 which is trans axle pressure control solenoid failure. This solenoid is not the A&B shift solenoids but upstream of the A&B solenoids. It`s location is inside the tranny by the dipstick. The A&B are easy to change....well almost!

Thanks

Gene

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...When the trans axle pressure control solenoid goes bad it lets the trans FLASH..run witout fluid and the clutch plates get destroyed/burnt.

Gene,

If I recall correctl, *bob said you can pump the transmission dry

without damage! Someone will chime in and correct/confirm this.

In case you think the shop may not be playing straight with you.

just a thought.

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...When the trans axle pressure control solenoid goes bad it lets the trans FLASH..run witout fluid and the clutch plates get destroyed/burnt.

Gene,

If I recall correctl, *bob said you can pump the transmission dry

without damage! Someone will chime in and correct/confirm this.

In case you think the shop may not be playing straight with you.

just a thought.

You can pump the trans dry when it is in park without damage. If you pump it dry while in gear, you will damage the clutch packs.

Kevin
'93 Fleetwood Brougham
'05 Deville
'04 Deville
2013 Silverado Z71

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... I have found a tranny at the boneyard for 400 bucks and it has 80K on it. The car is a 94 SLS 155K. What do you think?

Thanks

Gene

96 STS

93 ETC

66 ELDORADO

Gene, you got just a code P076, or you got some simptoms too?

Be sure it's not electrical.

Also (if you going to change transmission), remember that gear ratio of SLS is different of STS.

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... I have found a tranny at the boneyard for 400 bucks and it has 80K on it. The car is a 94 SLS 155K. What do you think?

Thanks

Gene

96 STS

93 ETC

66 ELDORADO

Gene, you got just a code P076, or you got some simptoms too?

Be sure it's not electrical.

Also (if you going to change transmission), remember that gear ratio of SLS is different of STS.

Make sure you get a 1994 SLS transmission, otherwise you will do a lot of work and still not have a running car. The SLS has a 3.11 ratio inside and the STS has a 3.71 ratio. If you try to put a STS tranny into an SLS car the computer will not recongnize or be able to compensate for the changes. Just what I have found ;) . Good luck.

Spence

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You can actually reach this soleniod to change it without dropping the tranny out of the car. I recently did this to my 97 d'elegance when I changed the tranny pump. You have to disconnect the steering linkage and the abs module from the cradle. There are some more misc items that have to be unbolted as well like the upper torque struts. afterwards you just place a jack under the left side of the cradle. You will remove all three left cradle bolts and loosen the right side. Next, lower the cradle on the left side to gain access to the side pan bolts. Yours sensors are underneath the side pan.

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You can actually reach this soleniod to change it without dropping the tranny out of the car. I recently did this to my 97 d'elegance when I changed the tranny pump. You have to disconnect the steering linkage and the abs module from the cradle. There are some more misc items that have to be unbolted as well like the upper torque struts. afterwards you just place a jack under the left side of the cradle. You will remove all three left cradle bolts and loosen the right side. Next, lower the cradle on the left side to gain access to the side pan bolts. Yours sensors are underneath the side pan.

WOW! How far must you drop the cradle to take the side pan off? Did you do this on the ground? When you say disconnect the steering linkage do you mean at the rack to be able to drop the carriage?

I would love to change my side pan gasket. I have been toying with the idea of changing my side pan gasket. Someone suggested that I remove the bolts slip the pan back as far as it will go, pull off the old gasket, and sneak the new gasket over the pan and into place. The only thought problem I have with that is, 1) how far will that pan come back, 2) if I have to scrape the old gasket off will there be room and 2A) how do I avoid the gasket material ending up in the tranny :blink:

You mentioned dropping the carriage and removing the side pan, and got my attention... Thanks

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