97 Sierra 4L60 transmission shifts hard after driving around 30 or so miles.

[TheNamesJuicy]

As the title states, I have a 1997 GMC 1500 with a 4L60 with 85,000 miles. The truck runs great and shifts fine up until I’ve gone around 30-40 miles or I assume gets to full operating temp. After it warms up it will shift hard from 1st to 2nd and then not as bad from 2nd to 3rd and completely fine from 3rd to 4th. I’ve checked the Transmission fluid and it is not too low or high. The fluid looks relatively clean with no burnt smell.

I’m not too sure what could be going on.

I’ve seen posts about the 96 models having an issue with the ground from the VCM and people have changed said ground with GM part no# 12167310 and it has fixed the issue. However GM claims this was only an issue for early 96 production. I’m seeing conflicting information about that. Some folks claim it’s only 96, others say it’s 96-99.

I’m hoping someone has gone through something similar or maybe has more info as to what could be going on with my truck. Thanks for your time!

 

[TheNamesJuicy]

Also, this is my first post in the forum. If I did something wrong please just let me know and I’ll fix it!

 

[NickTransmissions]

As the title states, I have a 1997 GMC 1500 with a 4L60 with 85,000 miles. The truck runs great and shifts fine up until I’ve gone around 30-40 miles or I assume gets to full operating temp. After it warms up it will shift hard from 1st to 2nd and then not as bad from 2nd to 3rd and completely fine from 3rd to 4th. I’ve checked the Transmission fluid and it is not too low or high. The fluid looks relatively clean with no burnt smell.

I’m not too sure what could be going on.

I’ve seen posts about the 96 models having an issue with the ground from the VCM and people have changed said ground with GM part no# 12167310 and it has fixed the issue. However GM claims this was only an issue for early 96 production. I’m seeing conflicting information about that. Some folks claim it’s only 96, others say it’s 96-99.

I’m hoping someone has gone through something similar or maybe has more info as to what could be going on with my truck. Thanks for your time!

Most of those trucks have bad grounds / issues with grounds so def worth checking. If/when you rule that out, Id look at the valve body (worn TCC regulator valve, very common) or 1-2 accumulator housing (broken springs). Problems that worsen as temps rise tend to indicate wear as opposed to parts breakage.

 

[TheNamesJuicy]

As the title states, I have a 1997 GMC 1500 with a 4L60 with 85,000 miles. The truck runs great and shifts fine up until I’ve gone around 30-40 miles or I assume gets to full operating temp. After it warms up it will shift hard from 1st to 2nd and then not as bad from 2nd to 3rd and completely fine from 3rd to 4th. I’ve checked the Transmission fluid and it is not too low or high. The fluid looks relatively clean with no burnt smell.

I’m not too sure what could be going on.

I’ve seen posts about the 96 models having an issue with the ground from the VCM and people have changed said ground with GM part no# 12167310 and it has fixed the issue. However GM claims this was only an issue for early 96 production. I’m seeing conflicting information about that. Some folks claim it’s only 96, others say it’s 96-99.

I’m hoping someone has gone through something similar or maybe has more info as to what could be going on with my truck. Thanks for your time!

Update, the CEL is P1870 which is Transmission components slipping.

 

[NickTransmissions]

Update, the CEL is P1870 which is Transmission components slipping.

Install the Fitzall valve for 95-2000 valve bodies.

That should fix it...If not, trans has to come out for overhaul.

 

[TheNamesJuicy]

Most of those trucks have bad grounds / issues with grounds so def worth checking. If/when you rule that out, Id look at the valve body (worn TCC regulator valve, very common) or 1-2 accumulator housing (broken springs). Problems that worsen as temps rise tend to indicate wear as opposed to parts breakage.

Before I get started, I regret to inform you I’m far from mechanically inclined. I went ahead and checked on the known ground issue with the 96’s. I DO have a wire in the #23 cavity of the blue connector. See attached photo.

If you don’t mind, are there other ground to look for? If so, where do I look?

As far as the valve body stuff goes that’s well beyond my wheelhouse. I’d definitely have to go to a mechanic.

Thanks for your help!

 

[TheNamesJuicy]

As the title states, I have a 1997 GMC 1500 with a 4L60 with 85,000 miles. The truck runs great and shifts fine up until I’ve gone around 30-40 miles or I assume gets to full operating temp. After it warms up it will shift hard from 1st to 2nd and then not as bad from 2nd to 3rd and completely fine from 3rd to 4th. I’ve checked the Transmission fluid and it is not too low or high. The fluid looks relatively clean with no burnt smell.

I’m not too sure what could be going on.

I’ve seen posts about the 96 models having an issue with the ground from the VCM and people have changed said ground with GM part no# 12167310 and it has fixed the issue. However GM claims this was only an issue for early 96 production. I’m seeing conflicting information about that. Some folks claim it’s only 96, others say it’s 96-99.

I’m hoping someone has gone through something similar or maybe has more info as to what could be going on with my truck. Thanks for your time!

Attaching some photos.

 

[TheNamesJuicy]

Attaching some photos.

 

[TheNamesJuicy]

Attaching some photos.

 

[NickTransmissions]

Before I get started, I regret to inform you I’m far from mechanically inclined. I went ahead and checked on the known ground issue with the 96’s. I DO have a wire in the #23 cavity of the blue connector. See attached photo.

If you don’t mind, are there other ground to look for? If so, where do I look?

As far as the valve body stuff goes that’s well beyond my wheelhouse. I’d definitely have to go to a mechanic.

Thanks for your help!

Address P1870 first as that is most certainly the problem. I was going to mention it initially but alsaw you didnt mention any codes (and harsh 1-2 shift has lots of causes that have nothing to do with P1870).

Take the truck to a reputable trans shop and have them do the work. They can check all the vehicle's grounds, including the PCM. No need to mess around with it at this point if you're not comfortable doing so.