(1988 Cutlass classic with 307 and TH200-R4) Transmission Slipping on the highway?

[Marinizzle]

Hi all, thanks in advance.
My cutlass runs strong and drives/shifts fine around the city (<80kmh) no problems. Yesterday coming home from work, i was getting on the highway and it accelerated fine and strong, but as soon as it hit 100kmh, it actually started to slow down and the rpms surged and increased unpredictably. Car sat at 80kmh and would not go over, also tried putting it in d, or 2 instead of overdrive, would not go above 80 while rpms kept surging. felt kinda like being on a boat hitting waves haha.

It makes me think its slipping but would it not also slip around town too? again it accelerated fine at WOT up hills and such no slipping noticed.
Anyone have an idea what could be wrong? 4th gear clutch maybe? hopefully trans isn't toast. The trans fluid is at the right level checked hot while running and is red and not burnt. Thanks,
Vlad

 

[Marinizzle]

Hi all, thanks in advance.
My cutlass runs strong and drives/shifts fine around the city (<80kmh) no problems. Yesterday coming home from work, i was getting on the highway and it accelerated fine and strong, but as soon as it hit 100kmh, it actually started to slow down and the rpms surged and increased unpredictably. Car sat at 80kmh and would not go over, also tried putting it in d, or 2 instead of overdrive, would not go above 80 while rpms kept surging. felt kinda like being on a boat hitting waves haha.

It makes me think its slipping but would it not also slip around town too? again it accelerated fine at WOT up hills and such no slipping noticed.
Anyone have an idea what could be wrong? 4th gear clutch maybe? hopefully trans isn't toast. The trans fluid is at the right level checked hot while running and is red and not burnt. Thanks,
Vlad

This one shows good acceleration, until it hits 100 then it stops:

IMG_6946.mov

drive.google.com

This one shows it stuck at 80 with the gas pedal floored, while the engine rpms increase:

IMG_6946.mov

drive.google.com

 

[78Delta88]

Vlad; I would do the simple things first. Do a filter change.

It doesn't sound like anything major mechanically wrong.

Sounds like just time for refresh.

 

[Marinizzle]

Vlad; I would do the simple things first. Do a filter change.

It doesn't sound like anything major mechanically wrong.

Sounds like just time for refresh.

Will do, Thank you

 

[78Delta88]

Sorry, was tired the other night didn't get to add a couple more comments. I did the conversions so 100km is a little more than 62 mph, which is well with in 2004R parameters.

The 2004R came out in a time when speed in the States was mandated 55 MPH, so from the factory it's not a speed monster. Driving a car designed for the "55 Stay Alive" days at the now highway speeds of 75 to 85 mph, is just going to overstress it and wear it out quicker.

It is TV sensitive but that sounds ok by your description. That's why I mention change filter.

The other I wanted to mention is when doing the filter change try a Transgo shift kit if you feel comfortable with that. When you open up the "apply" ports to the clutches and it will show that in the shift kit, you get more fluid to the clutches.

This doesn't increase pressure per-se, but does get the fluid to clutch pack quicker with an adequate pressure. In the interim it can help the transmission. So, basically you have a unit that is aging out and needs a refresh. Same for Torque Converter.

Some of what you mention shows Torque Converter as well as some normal internal wear and age issues.

If you pull the trans and don't want to go full rebuild... Pull the trans and get a new lock up torque converter 2300 stall (there or about). Pull the front pump and install the .45 or .50 inch boost valve and replace the 8 vane pump with a 13 vane pump. Replace the two overdrive clutches and put a new seal on the overdrive piston, and front pump seal. That's about as far as you want to go without doing full rebuild.

You will notice that the piston and other seals are getting harder and brittle. This is due just to age and use. If you use the "transmission in the can" type stuff it will soften and swell the seals. So don't use it it until you get to the point of a few months prior to full rebuild, just to keep it going.

Just stay within your tools and comfort level. The good thing is your low/reverse pack sounds ok. Your other packs sound ok but starting to slip a bit under load.

 

[L05edSS]

Hi all, thanks in advance.
My cutlass runs strong and drives/shifts fine around the city (<80kmh) no problems. Yesterday coming home from work, i was getting on the highway and it accelerated fine and strong, but as soon as it hit 100kmh, it actually started to slow down and the rpms surged and increased unpredictably. Car sat at 80kmh and would not go over, also tried putting it in d, or 2 instead of overdrive, would not go above 80 while rpms kept surging. felt kinda like being on a boat hitting waves haha.

It makes me think its slipping but would it not also slip around town too? again it accelerated fine at WOT up hills and such no slipping noticed.
Anyone have an idea what could be wrong? 4th gear clutch maybe? hopefully trans isn't toast. The trans fluid is at the right level checked hot while running and is red and not burnt. Thanks,
Vlad

when you run it around town are you in D or OD? in D the doesn't lockup and if gonna drop the pan get a new pressue switch & TCC solenoid maybe extra $40?

 

[Marinizzle]

when you run it around town are you in D or OD? in D the doesn't lockup and if gonna drop the pan get a new pressue switch & TCC solenoid maybe extra $40?

od

Yes i'm going the route of partial rebuild with the parts 78delta88 and you suggested as well as a 2300 lockup stall

 

[olds307 and 403]

I like the big Transgo shift kit, includes the servo and .500" boost and larger reverse valve. What rpm does it shift at full throttle? My 88 shifted at 3000 rpm. The green line bias spring included in shift kit, raises full throttle shifts a few hundred rpm. The Transgo hardened pump rings, pump slide spring and new stator also aren't a bad idea.

 

[Marinizzle]

I like the big Transgo shift kit, includes the servo and .500" boost and larger reverse valve. What rpm does it shift at full throttle? My 88 shifted at 3000 rpm. The green line bias spring included in shift kit, raises full throttle shifts a few hundred rpm. The Transgo hardened pump rings, pump slide spring and new stator also aren't a bad idea.

I actually dont have a tach in it so i wouldn't know, I would say it could be a little higher though.

 

[Marinizzle]

Sorry, was tired the other night didn't get to add a couple more comments. I did the conversions so 100km is a little more than 62 mph, which is well with in 2004R parameters.

The 2004R came out in a time when speed in the States was mandated 55 MPH, so from the factory it's not a speed monster. Driving a car designed for the "55 Stay Alive" days at the now highway speeds of 75 to 85 mph, is just going to overstress it and wear it out quicker.

It is TV sensitive but that sounds ok by your description. That's why I mention change filter.

The other I wanted to mention is when doing the filter change try a Transgo shift kit if you feel comfortable with that. When you open up the "apply" ports to the clutches and it will show that in the shift kit, you get more fluid to the clutches.

This doesn't increase pressure per-se, but does get the fluid to clutch pack quicker with an adequate pressure. In the interim it can help the transmission. So, basically you have a unit that is aging out and needs a refresh. Same for Torque Converter.

Some of what you mention shows Torque Converter as well as some normal internal wear and age issues.

If you pull the trans and don't want to go full rebuild... Pull the trans and get a new lock up torque converter 2300 stall (there or about). Pull the front pump and install the .45 or .50 inch boost valve and replace the 8 vane pump with a 13 vane pump. Replace the two overdrive clutches and put a new seal on the overdrive piston, and front pump seal. That's about as far as you want to go without doing full rebuild.

You will notice that the piston and other seals are getting harder and brittle. This is due just to age and use. If you use the "transmission in the can" type stuff it will soften and swell the seals. So don't use it it until you get to the point of a few months prior to full rebuild, just to keep it going.

Just stay within your tools and comfort level. The good thing is your low/reverse pack sounds ok. Your other packs sound ok but starting to slip a bit under load.

Thanks for the info. I found an overdrive clutch on CK performance, but they also have an "Override clutch" and "Overdrive Steel plates". I don't know a whole lot about automatic transmissions, which one of these will I need to get?

Also, any recommendations on which torque converter brands to avoid? Thanks