Transmission Questions.

With 178,000 well cared for miles I think it's time for a rebuild on the tranny.
My question is what do I want replaced as far as inner parts? TCC, etc....

if the transmission is operating properly IMHO the best thing you can do is switch to Dexron VI fluid, fresh filter too... and NEVER switch back (the TCC clutch won't like it if you do).

I would not bother with a rebuild.

My OE 4t65e had a tcc lockup problem at about 95,000 miles. I had it locally rebuilt by a guy who does racing and fleet transmissions. Had his hardheaded partner not switched back to Dex VI I'd still be driving on that rebuild.

Really I would not bother cracking open a working Eaton / Turbohydramatic for PM unless it was sending failure signals. On these FWD transmissions I would definitely switch to Dexron VI in a heartbeat, though. No additives. Just the Dex VI please.

Here's my transmission question for the day:

I notice, under near to full WOT, when my Riv shifts from 3rd to 4th gear, I feel it. And I dont like it. Is it supposed to shift noticeably hard? It's not like OMG something is broke, but it shifts kinda hard sometimes. no problems down shifting or shifting from any other gear. Just from 3 to 4 under ~WOT application.

Am I a hypochondriac or does this sound like the beginning of something?

3rd to 4th at wide WOT? How fast were you going?

I dont know at what speed the car shifts, probably just when I soft off the pedal for a moment.
probably @ 80+ I can recreate it.

The car should be shifting from 2nd to 3rd gear at WOT around 88 mph. The speed limiter will kick in before it will shift to 4th gear on a stock pcm. https://rivperformance.editboard.com/t162-need-info-and-specs-for-your-riviera

I think you misunderstood me. When I am in 4th gear and then go into WOT I drop down to 3rd gear Maybe around 70mph. Then, when I get up to 80+ and lay off the pedal, I shift back up to 4th but i can feel that shift more than any other shift in my transmission. I can only describe it as harsher than the rest. From 3rd to 4th after WOT.

charlieRobinson wrote:

I think you misunderstood me. When I am in 4th gear and then go into WOT I drop down to 3rd gear Maybe around 70mph. Then, when I get up to 80+ and lay off the pedal, I shift back up to 4th but i can feel that shift more than any other shift in my transmission. I can only describe it as harsher than the rest. From 3rd to 4th after WOT.

If that bugs you, you can see a Buick dealer or a transmission shop to apply the recalibration of the 3-4 shift.

Albertj

albertj wrote:

if the transmission is operating properly IMHO the best thing you can do is switch to Dexron VI fluid, fresh filter too... and NEVER switch back (the TCC clutch won't like it if you do).

I would not bother with a rebuild.

My OE 4t65e had a tcc lockup problem at about 95,000 miles. I had it locally rebuilt by a guy who does racing and fleet transmissions. Had his hardheaded partner not switched back to Dex VI I'd still be driving on that rebuild.

Really I would not bother cracking open a working Eaton / Turbohydramatic for PM unless it was sending failure signals. On these FWD transmissions I would definitely switch to Dexron VI in a heartbeat, though. No additives. Just the Dex VI please.

Is a flush and switch to Dextron VI a good idea for longevity and preventative maintenance in general?

If so, why? (Just curious to understand the difference than stock and why)


I ask this in the context of my 43k 95 Riviera that I just picked up after having sat undriven(practically) for 4ish years and what preventative maintenance might be recommended given that scenario. I'd bet that the trans fluid has never been flushed and filter changed in its 18 years.

I know some folks say you shouldn't even flush many modern auto transmissions if they are working fine, fluid looks good and maintaining fluid levels as that can introduce problems by dislodging debris. Another "ain't broke don't fix it" example I guess *shrug*


Thanks,
Al

I have a problem with my TCC refusing to stay engaged and eventually causing the Tranny to overheat and fall into limp mode losing overdrive and causing very firm shifts. Last summer, we flushed the fluid and put in Dex VI, and installed a tranny cooler. The fluid doesnt seem to overheat anymore and the car shifts perfectly even after drives of up to 25min. (No limp mode) im not sure if its mostly the cooler but the DEX VI has been great for me. My car is not a daily driver but from the 500 miles or so Ive had the DEX VI, it seems like a worthwhile change.

Have a problem or had a problem?

Have a problem. Its still not fixed but I just drive the car in third around town and no problems. Ill use 4th on the thruway as long as Im not going far. It doesnt really affect the car in city driving. My dad and I will try a new torque converter and TCC and see if that fixes everything.

Or I may just have the TCC disabled if possible on the 95. I believe AA did it on his with success and still getting good gas mileage but Im not sure how the 4T60-E differs for that

I don't know if the 95 can be disabled. Not sure what tuner you would use. My mileage isn't terrible (20 MPG avg) but its not great, either. Used to get 35 mpg freeway, now get 25 at best. City MPG is the same.

Yes, thats what Im worried about. We've found a couple tuning programs for OBDI that work but I have no idea what you can do with the Trannys! I agree, it would be nice to have that high highway mileage capability. We do have the cars original transmission sitting around. Maybe it would be worthwhile to save up and have that completely rebuilt.

AA wrote:

I don't know if the 95 can be disabled. Not sure what tuner you would use. My mileage isn't terrible (20 MPG avg) but its not great, either. Used to get 35 mpg freeway, now get 25 at best. City MPG is the same.

Sorry for a quick thread detour....

Did you really get 35mpg with freeway driving!?

I still haven't got our 95 back on the road yet, but I was hoping for 25-27 highway. Can I expect 30s if the car is in good running condition? That would be excellent news if so!

Al

Quote :

Sorry for a quick thread detour....

Did you really get 35mpg with freeway driving!?

I still haven't got our 95 back on the road yet, but I was hoping for 25-27 highway. Can I expect 30s if the car is in good running condition? That would be excellent news if so!

Al

Absolutely. There were also multiple confirmed 37 and 39 MPG trips (as in, I used only 3.4 gal to cover 130 miles). Like most cars, Rivieras are capable of amazing MPG numbers if driven carefully. I usually say 35 MPG highway, because that's more realistic without getting too ridiculous. By ridiculous, I mean driving techniques that most people wouldn't feel comfortable with on a regular basis.

Some people hear these high MPG numbers and think they too can expect it everyday without trying. I say get past the idea that MPG comes the car or the engine. Probably 50% or more comes purely from driving style and technique. Getting close to 40 MPG is extremely challenging, but it's possible with a very controlled driving style. Is it worth it? Imo, not really if you're looking to save money. It is however personally satisfying to know you can do it!

Detour continues here: https://rivperformance.editboard.com/t3481-faq-hypermiling-modifications-techniques