EL CAMINO Clunking auto trans under load when warm and low rpm

[schwim]

Hello there!

87 with 305 and overdrive auto

I haven't owned an auto trans vehicle in over 20 years so I'm a bit rusty, forgive me.

This new-to-me 87 has an issue where when the vehicle warms up, it's got a jerking issue, as if the trans is completely disengaging and re-engaging rather violently, not softly, sort of like a repeating clunk. As soon as I give it a bit more gas, it goes away and the trans seems to behave like normal. I've checked the fluid and it's not burnt smelling and it's a bit above the full mark when warm and running. I've no record of previous services/repairs.

What should my first step be in diagnosing the issue? Any known problems that I should look at first?

Thanks for your time!

 

[83StreetMachine]

First things I'd check are the trans mount and U-Joints.

 

[schwim]

First things I'd check are the trans mount and U-Joints.

thanks very much for the help! I put it on the lift and the driveline is in good shape, in regards to joints and mounts.

By clunking, I believe I'm misrepresenting the issue. It feels like a hard slip then re-engagement. The clunk is when it re-engages suddenly.

 

[Clone TIE Pilot]

Check the TV cable adjustment.

 

[ELCAM]

First thing to check is oil level, is it the correct dipstick, is it really full it will do this when it is cavitating then it slams into gear when it gets to pumping oil again.

Second is the throttle valve cable and valve if it is misadjusted or a valve is sticking the pressure will be low and will increase with RPM till there is enough pressure to engage the clutches.

 

[schwim]

Thank you both so much, I will get it in the garage and start going through the cable adjustment process. Fingers crossed it's something like that and not something more serious.

 

[79 USA 1]

Does it seem to want to or does it stall when coming to a stop? Similar to a manual transmission that you are late on pushing in the clutch when coming to a stop.
Could be the torque converter lock up solenoid. Requires dropping the pan to replace but is a common problem in the 200-4r that is a fairly easy repair.
Had to replace them in my 88 Monte Carlo SS as well as my 86 El Camino just after purchasing them. The 1-2 shift felt like a double shift as the converter locked then lugged the 2-3 and 3-4 shifts.

 

[schwim]

Does it seem to want to or does it stall when coming to a stop? Similar to a manual transmission that you are late on pushing in the clutch when coming to a stop.
Could be the torque converter lock up solenoid. Requires dropping the pan to replace but is a common problem in the 200-4r that is a fairly easy repair.
Had to replace them in my 88 Monte Carlo SS as well as my 86 El Camino just after purchasing them. The 1-2 shift felt like a double shift as the converter locked then lugged the 2-3 and 3-4 shifts.

It's fine at idle and when coming to a stop, just under load is when the issue occurs. It seems to have gotten worse so I'm going to take it to a shop as I feel ill equipped to sort this before doing irreparable damage to the trans.

 

[Kamloops cutlass]

Please let us know what the the gremlin was when you find it

 

[schwim]

Please let us know what the the gremlin was when you find it

I got it back yesterday and the the crazy shift/clunk issue is gone but replaced by a crazy slow 2/3 shift. The mechanic stated he did everything he could in fiddling with the tv cable and pressure, he suggested I put a shift kit in the trans to give it more positive shifting as they're all incredibly soft and sluggish.

Anyone have any input, suggestions or concerns regarding putting a shift kit in this? Has anyone done it? I really don't like how softly it shifts and would like a bit more of a positive shifting experience with it.