Looking for a better $8D

[JeepsAndGuns]

I've read about European heavy trucks that are automatic manuals... Manual transmission that is computer shifted using air solenoids. OE's are working their butts off trying to design automatic trans with minimal fluid but really this is a more cost effective answer imo. And to make life easire add a torque converter like Chrysler did in the '50s. Can idle in gear that way.

They have those over here. The eaton fuller autoshift and ultrashift. The autoshift still had a clutch and clutch pedal, all you had to do was push it in to stop, and let out to go, all other times the trans sfhifted itself. The ultrashift they took away the clutch pedal and installed some type of automatic or centafugal clutch. We used to have a international 4300 at work that had to ultrashift. It didnt know the first thing about shifting. It would upshift too soon, and wait way too long to downshift. It sucked. 98% of the time I put it in manual mode and just shifted it with the buttons.


I thought vehicles that had the 7730/7727 and 8d had the 700r4, and I thought that was a non computer controlled transmission? (except for the TCC) It was confusing me because some xdf's called it CARS, while others called it the shift light.

[Six_Shooter]

'7730/'7727 equipped vehicles did use non computer controlled transmissions. 700R4, TH125, and a few others.

[EagleMark]

I thought vehicles that had the 7730/7727 and 8d had the 700r4, and I thought that was a non computer controlled transmission? (except for the TCC) It was confusing me because some xdf's called it CARS, while others called it the shift light.

Your reading the XDF like it was a accurate shop manual. It is not, it,s a mask made by a unknown human, some may be accurate and some may not. This is a point where you need to look at hack and see what is really there.

Since the ECM was not a PCM and had no control over transmission shifting, I would say the shift light is a more realistic guess?

I've only seen CARS in LT1 XDF, it is a PCM with 4L60E computer controlled trans, there's obviously others. I don't understand how CARS made it into a ECM that never had a computer controlled trans? So shift light could be an option for the manual trans?

[RobertISaar]

CARS existed back into the 8D and possibly earlier days.... it's just control of a relay (IIRC) that's used to block all shifter positions except for 1st and 4th on the T56 and i think one other 6 speed manual.

[1project2many]

IIRC only last year of TPI Vette had 6 speed trans... 1991. CARS was called CAGS, Computer Aided Gear Selection. Prior to that GM used weak Doug Nash 4 speed OD transmission which was really a T10 with an overdrive planetary set on the back. Same wire and ecm controls used to operate planetary solenoid as TCC in auto trans. Neat idea but ultimately too weak for serious performance. And funny too, because similar idea 3 speed w/ overdrive manual used from '50s to mid '60s was also too weak for serious performance.

We used to have a international 4300 at work that had to ultrashift. It didnt know the first thing about shifting. It would upshift too soon, and wait way too long to downshift. It sucked.

They're pusing to use "progressive shifting" which is earlier shifts based on torque curve. Doesn't feel as fast and seems to lose power but numbers say otherwise time and again. Computers programmed this way can be pretty blind to what the real world needs are.

[RobertISaar]

looking through alldata diagrams.... 90 corvette L98 shows the 1-4 upshift relay.
89 shows it as well.
88 and earlier has some other type of relay, "overdrive relay", i don't think it serves the same purpose though.

so, i'd bet it's somewhere in the 6E code as well.

and i've always wondered: so use the clutch for shifting 1-4, but shifting 4-5 and 5-6 requires no clutch movement, right?

[JeepsAndGuns]

Your reading the XDF like it was a accurate shop manual. It is not, it,s a mask made by a unknown human, some may be accurate and some may not. This is a point where you need to look at hack and see what is really there.

I have been checking the hack, it calls it CARS too. Theres actually a lot of parameters for cars, and a lot of them have question marks next to them, I guess even the person who wrote the hack didnt understand them.

Every time I have copy and pasted in a parameter from other xdf's, I would find it in the hack, make sure its the same/correct, then use the parameter finder to make sure its not already in my xdf and just called something else, then I would copy and paste. I would also edit the title and add ** to the end, so I can keep track of what I have added. It has increased in size from 206kb, to currently 253kb, still some more to go. At the rate I am going, I might be done by the end of the month...lol

[JeepsAndGuns]

CARS existed back into the 8D and possibly earlier days.... it's just control of a relay (IIRC) that's used to block all shifter positions except for 1st and 4th on the T56 and i think one other 6 speed manual.

What the heck is the purpose of that?!?!?
If there was something as stupid as that on a vehicle I owned, it would quickly be disabled.

[EagleMark]

It's a communist plot against the American way...

[1project2many]

The purpose of CAGS / CARS was to improve CAFE compliance. Govt watches average fuel economy for a company's entire fleet of vehicles. Gas guzzlers like Cadillac and hi perf Camaro need to be offset by Aveo's and Metros to keep numbers in line or else big fines. CAGS caused gearshift to bypass 2nd gear position and drop into 4th. This improved economy in EPA mileage testing and helped CAFE.

looking through alldata diagrams.... 90 corvette L98 shows the 1-4 upshift relay.
89 shows it as well.
88 and earlier has some other type of relay, "overdrive relay", i don't think it serves the same purpose though.

Thanks for the clarification. Something has stuck in my mind about a 91 Vette with 6 speed though. Maybe it's just that that was the best TPI plus 6spd to own. Anyway, the overdrive relay is for the Doug Nash trans. http://www.5speeds.com/dne.htm Also called "4+3" as the OD unit could be engaged in 3 of the forward gears.

All shifting required clutch. CARS is attached to the shifter and affects the shift gates. Nothing is affected internally.

Mark, just because you're paranoid doesn't mean they're not out to get you. The best boy scouts know the value of being prepared.

[JeepsAndGuns]

Anyone have the error code listing for a $8D car? I'm thinking there are a couple in this XDF thats not actually used.

[JeepsAndGuns]

No one has a error code list? I would much rather trust a list from yall than a random list from the internet. I think there are a couple in the xdf that not correct, or not used. Also want to double check the other ones.
Right now thats the only thing holding me up.

[RobertISaar]

alldata list for 91 firebird w/5.7TPI:

13
14
15
21
22
23
24
25
32
33
34
41
42
43
44
45
46
51
52
53
54

[JeepsAndGuns]

I have the following error codes in there I dont think are used:

16- DIS fault
36- DIS missing signal
55- fuel lean moniter
56- vaccume sensor


On your list above, you dont have, but I do have:

12- no DRP's
62- engine oil temp high
both of these codes are active on ANHT (90 vette)

Is there a reliable site that has a listing of the error codes and what they are, for the camaro/firebird/vette/anything else using $8D?
I want to double check all the codes, then I will pretty much call it done, and let some here check it over before we post it up.

[1project2many]

There are no distributorless ignition codes active in $8D. I've never seen 55 or 56 set. 12 is active in most GM OBDI cals but a scantool won't show it as it's always there when the key is on and the engine is off.

http://tech.corvettecentral.com/2011...trouble-codes/
About 1/2 way down the page.

http://www.corvetteguruforum.com/mod...post_id=171640
top of the page

http://www.iroczone.com/2009/10/deco...trouble-codes/
Dedicated to F car codes