Shifting Patterns/Sequence for 1988 C4

[cajuncorvette]

A couple of questions from a newbie regarding my 1988 C4 automatic.

1) What is the normal shifting pattern for an '88 automatic -- meaning at what approximate speeds should the car shift from one gear to another?
2) In an automatic, does the driver prompt the tranny to shift?
I am without a manual and am a newbie to Corvette, and I see an upshift arrow (economy) on my dash -- assuming this is for manual.
3) What transmission fluid and filter do you recommend?
4) What coolant do you recommend?

Thanks for all your help. I am really enjoying my car and learning a lot thanks to everyone here. Cajun

 

[Baldie88]

Hi Cajun,

As far as the transmission shift points, all I remember is that just normal pulling away from a stop sign, mine will shift out of first at about 15-20mph. But if you get on it, it won't shift till about 45mph. Just normal driving you will probably be in 4th at around 45mph. All to get the best mileage for the EPA rating.

And you are correct, the upshift arrow on the dash is just for the manuals.

As far as transmission and coolant recommendations, I just buy whatever was on sale at Auto Zone and have had no problems. I will tell you that when I first got the car I did drop the transmission pan and replaced the fluid and filter and it was a b___h!. I had more fluid on me than in the pan. I am going to my local Chevy dealer and have them do a powerflush like they have done with my other cars in a couple of weeks and I have been satisfied with the powerflush. I have always done my own coolant flush with Prestone but I've notice some scale building up so I'm going to have the dealer do a powerflush of the coolant also. I guess I'm getting old because I use to always do this kind of service.

If you don't have a manual you might consider buying the service manuals. I found mine on eBay. I am including 2 links to both the service manual and electrical supplement I found.

1988 Corvette Service Manual:eBay Motors (item 200355857151 end time Jun-30-09 11:09:04 PDT)

1988 Chevrolet Corvette Electrical Diagnosis manual:eBay Motors (item 170338759626 end time Jun-29-09 12:59:26 PDT)

I also saw someone is selling both for $75 plus $25 shipping and that is a complete ripoff (hope it's not someone on CAC). I paid $35 for both manuals about 7 years ago.

I also bought an owner's manual from Helms but after getting 3 and all were missing the same chapters I just forgot about it. Anything you need to know will be in the service manuals.

Good luck.

Ron
"Baldie88"

 

[cajuncorvette]

Follow up

Great information! I am asking about the shifting patterns because this car is very different from any other car I have ever owned. Would you believe I had never driven or ridden in a Vette before I bought this one? Yes, I literally bought the first Vette I had ever been in. When I bought the car, I took it first to a local Vette dealer in Dallas. The man explained that this particular model (not sure if he referenced the engine or the transmission) would shift up at higher speeds after acceleration -- meaning that if I am driving at 50-55 mph, the engine is accelerating as I depress the pedal, but the car actually shifts to the higher gear when I ease off the accelerator. I don't notice it at other speeds -- just the highway speeds -- over 50 or so. Is this an overdrive type of feature? I have had the car checked twice by GM mechanics -- both say this is common for this car.
The car runs and drives perfectly, but I am not used to the shifting at the higher speed. Thanks again! Yesterday, I took the targa top off for a cruise and got caught in a rainstorm. I'm not quick with the wrench, either! LOL
Cajun

 

[roger longman]

Hi Cajun, a Corvette specialist told me to keep out of overdrive unless I was doing over 55 mph. I had found that under that speed the engine wasn't happy with that high a gear ratio when pulling. It also changed gear at lower rpm when in overdrive. Now I'm wondering whether there's something wrong with my Vette ! Pherhaps one of the guys could let me know? Also the arrow on the dash is indicating you could be in a higher gear (overdrive) for economy driving. Roger.

 

[cajuncorvette]

Hope I Am Not Confusing You .....

I appreciate your reply. I should have just asked a simple question:

How should a C4 (1988 automatic) shift into overdrive (or highest) gear?
My car shifts after I stop accelerating -- or somewhere near 58 mph. In other words, I can "cause" a shift by letting off the accelerator. If I don't let off and continue to let the engine build, it will shift around 58 mph on its own but it does not seem to want to .... or the sound of the engine is just causing me to be chicken. I usually let off the pedal around that time, but I think it does shift anyway.

My question is -- is this shifting normal? I don't know because this is my first Corvette. No other car I have ever owned shifts after I let off the gas .... so I am concerned. Thanks!

 

[roger longman]

Hi Cajun, yes it's normal, it depends on how much throttle you're giving it, although mine shifts into overdrive at about 48 mph if I'm going light on the pedal. Roger.

 

[cajuncorvette]

Response

Hey, Roger
I just spoke with a GM mechanic. He said I might need a transmission flush and fluid/filter change. I hope that is all. Here's the deal: My car shifts fine except into what I think is 4th gear. As I accelerate, the engine revs, and I think it sounds like it is time to shift ... but it doesn't. It is around 58 mph. If I let off the gas, it will shift smoothly and run so smooth as if in overdrive or something. The car has no issues except for this. Normal? not normal?
Thanks!

 

[roger longman]

Hi Cajun, OK a bit of a correction. Just took it for a spin. Light on the pedal itshifts into OD at 48 mph heavier on the pedal 58 mph. In OD at less than 55mph and under load it is not happy, that's at 11-1200 rpm,dead flat or on over run it's fine. When the engine warms up it gets more noticable and misses a beat. The transmission was replaced by Dick Guldstrand less than 4000 miles ago,so fluid is not a problem. I guess your mechanics answer was of the same ilk as "change the wires and plugs" not necessarily the answer but not a bad idea. Could someone else please chime in on this one? Roger.

 

[cajuncorvette]

I am going to drive the car tomorrow and will post any updates

Can anyone help Roger and me with this concern? Thanks!

 

[vetteoz]

Sure you are not feeling the convertor lock up when you back off?

 

[cajuncorvette]

How would I know? Can you help me troubleshoot?

The Vette enthusiast I was with when I bought the car last fall says the car has had an aftermarket torque converter upgrade. Could that intensify this shift issue? I am planning to drive the car again tomorrow. Any suggestions on what I should do/try during the drive so I might identify the issue? Thanks so much!

 

[cajuncorvette]

Updated Information on C4 Shifting

Okay, here we go. As a Corvette newbie, I am not sure what exactly I am talking about, so I may have started a thread (and confusion) by not realizing exactly how a Vette performs.

Today, I took my '88 out on the highway. Here are the shifting patterns I observed: 1st 0-
2nd shifts at 17mph
3rd shifts at 37 mph
4th shifts at 67 mph

Now, what I was hearing was the noise of the engine (RPM's building) as I increased speed from 50 - 65 -- not quite fast enough to shift at 67 -- but the primary span I drive in on the highway. As I would reach 60 or so, the sound of the engine made me think it should shift -- I would let off the pedal, and the car would "shift" -- does not feel like a real shift but there is a smooth transition - engine sound drops - and car cruises smoothly at the speed where I removed my foot from the pedal.

Now, I have never driven a Vette -- or any loud car before, so I know I am not using the correct terms. I don't know what the torque is, or what throttle means, but I am doing my best to describe what my car does.

Is this normal? And I thank you for all your kindness, wisdom, and patience! Cajun

 

[roger longman]

Hi Cajun, You can of course look up the technical meaning of these words but in general terms torque is the shear power of the engine and is normally greater in a long stroke low revving engine, such as the corvette. European and japanese tend to be short stoke high revving engines such as those found in racing cars (also 2 stroke engines). For throttle read accelerator,they are not the same, but in this context it makes no difference. Hope this helps. Roger.

 

[cajuncorvette]

Thanks! So, what do you think of the shifting pattern?

It appears my car shifts just fine. (I think, anyway.) I am letting off the accelerator because I hear the engine building RPM's as I near the speed limit
(usually at 55 to 65 around here). So, I am never actually shifting into the highest gear. I let off the accelerator because I thought, being a newbie, that my car was not shifting. It does -- at 67 MPH -- and with no issue. But since I usually don't hit that speed in daily driving ( and with traffic on the interstate), I did not know until I checked today.

Now, my real question is this: what is happening when I am around 55- 60 or so -- RPM's up, engine revved, and I ease off the pedal -- and the car appears to shift into some type of cruise mode -- engine quieter, car seems almost on autopilot compared to moments before when I was accelerating.
Is this an overdrive? Normal? Thanks so much for your time and patience! and knowledge!

 

[roger longman]

Hi cajun, Yes it's nomal, you're going into overrun. Roger.

 

[cajuncorvette]

Thank you!