View Full Version : 1980 Z28 4sp
10-31-2003, 02:32:00 PM
Well from all the info on 4sp cars here.
I just need to know how strong is the transmissions from these cars are.
I can see it is says "13-04-065-904" right on it. and it's a Borg Warner.
How strong is it?
10-31-2003, 07:10:00 PM
It isn't as strong as a Muncie M21, or any Muncie probably, but much better than a Saginaw. It won't have the gas mileage of the 82 and newer manual transmissions, but it'll be stronger than them. I guess it will probably be in the middle of the road, so to speak.
11-01-2003, 09:29:00 AM
I would argue the strength of the ST10 is at least equal to the Muncie assuming the gear ratios are the same.
The ST10 is available with steel mid-plates, nickle gears and nodular iron cases making such a set up vastly stronger than any factory Muncie with equilvelant gearing. However, most ST10s did not come this way.
The problem for comparison sake is that most Muncie transmissions come with low numeric first gears and close ratios while most ST10's were wide ratio, aluminum case models with a deeper first gear. Accordingly, the "typical" Muncie would probably have more torque capacity than the "typical" ST10.
That being said, I will stand by my original statement that if you have the two transmissions, both with aluminum cases and both with the same gears, the ST10 would be the equal of the Muncie intorqu capacity.
11-01-2003, 04:15:00 PM
I'm no transmission guru, but I thought all ST-10's were close ratio. I do know that all Z-28's from 77 - 81 that had 4-speeds were called out on the option list as close ratio.
I still don't think the ST-10 is as strong as the "Rock Crusher". I'd like to think that since I have one, but I don't so.
11-01-2003, 06:02:00 PM
i belive that there was an option for a close-ratio and a wide-ration in '77 but only the z28 got the close-ratio.
11-02-2003, 04:40:00 AM
Exactly my point. Yes, your rock crusher is stronger but only by virtue of it's gear ratio. Only certain ST10's came with gear ratios close to the Muncie. Those that do are IMHO every bit as strong as a similar geared Muncie. I'm not slamming Muncie here but saying there are ST10's as strong or stronger.
If you got the service replacement ST10, I believe you got a nodular case, iron mid-plate and nickle gears which would be a superior box to most any Muncie regardless of gear ratio.
ST10's came with first gears from 2.64 up to 3.42:1. The close ratio 2.64 geared ST10 would be a wide ratio by Muncie standards. Close ratio meant something entirely different in 1969 than 1979. In 69 a close ratio box would have a 2.20 gear. By 79, close ratio meant a 2.64 - 2.88 gear.
11-02-2003, 04:31:00 PM
150.000+ miles on my 77 1/2, Super T-10 w/2.64 1st gear, hanging on the back of a ZL-1 engine. Almost 20 years and not a single problem.
80.000 miles since a fresh trans-build on my '80 Same trans spec, this time with a GenVI 454, no problems.
Both cars driven as a Z28 should be.
9 second S/G '61 Vette, Super T-10.
I don't like mommy shifters. Need 3 pedals in my cars.
11-02-2003, 05:37:00 PM
O.K., I know when I've been beat. I guess it's good to know I have that good of a transmission. Do you think the BW is better than the Siginaw? Do think it'll hold up better than an auto? I don't think the 4-speed is going to run down the strip as fast as an auto. Of course, that depends on who's shifting. I'm with Aero on the 3 pedal thing. My last Z was an auto, and I really like shifting this car better. I think it's a much funnner car to drive. In my opinion, more charisma.
11-02-2003, 08:18:00 PM
I love charisma in stop and go freeway traffic. Burned up my clutch when we all got caught in a forest fire in the Santa Monica mts. No pun intended. Took 4 hours to go 5 miles.
Bums were coming up on the freeway and threatening the drivers for money, and in the middle of all this my clutch blockside pivot ball broke.
I don't care, I don't want a mommy shifter.
11-02-2003, 08:28:00 PM
will an S T-10 outlast an auto?
All kidding aside, I think so. This is only my opinion, but in all the years I've had my cars my transmissions just keep on keeping on, where mommy-shifters in friend's cars occasionally would be in the shop or on the driveway. Clutches seem to last me about 5-6 years, same as the tires. Hmmm, wonder if there's a connection there.....
Only as a matter of record and for thought, the Muncies in my old '66 SS-396 Shovelle would complain once in a while, same as the one in my LS-7 powered '55 back in the days.
I never worry about my trans.
Well, now wait a minute... I did break a front bearing retainer when the clutch got all screwed up from the forest fire. It wasn't the transmission's fault, and even with the busted retainer it still ran fine. Tough trans, IMO.
11-02-2003, 10:30:00 PM
<font face="Arial,Verdana" size="2">Originally posted by Als78z28:
Do you think the BW is better than the Siginaw? </font>
Definitely. The saginaw has reverse gear in the main case instead of in the tail housing like Muncies and T-10's. So gears have to be thinner and weaker. ST-10's come in 2.4, 2.6, 2.8 and 3.4 1st gear models. Reason the units with deeper gears are more prone to breaking is the greater load from the higher torque multiplication of the deeper gear. Same thing applies to Muncies (2.2 is more durable than 2.5) and T-5's, etc. But a 2.4 or 2.6 ST-10 is about as strong as a M20 Muncie (2.5).
11-03-2003, 12:31:00 AM
O.K., let me get this straight, if you have a 2.64, it's going be higher geared than a 3.42. And it's going to be considered closer ratio of the two.
If this is true, then I wouldn't want anything any lower, because mine is 2.64 and I don't even need 1st gear half the time (still use it though so I get more shift time, lol). I guess it'll hold up better too.
Did you like the 2.64 1st of the 77, or the 3.42 1st of the 80, Aero? I guess it would be hard to tell, because in the 77 you had 3.73 rear gears and in the 80 you probably have 3.08's.
That's another thing, did they go up in rear gears in 80 for gas mileage and go down in 1st gear ratio to compensate? I guess this would be hard on the tranny.
What 1st gear did the Rock Crusher have?
11-03-2003, 01:57:00 PM
I believe the ST-10's that came from the 80-81 Z28's have a 3.42 first gear and 3.08 rear ends. If I swap the rear gears to 3.73 and have increase in power to lets say 330HP
is this tranny acceptable? Would first gear be too much?
11-03-2003, 02:05:00 PM
1978-1981 Canadian-destined Z28s all got 3.73 rear gears with the close-ratio ST-10, 3.42's came if you ordered an automatic. As all these Z's got the "close ratio" tranmission- you would have a 2.64 first gear.
11-03-2003, 02:28:00 PM
Really? Well I hope that is true..I have a CDN Z28. I thought that 80/81 Z28's 4sp's had 3.42 First 2.28 Second 1.45 Third and 1.00 Fourth. and 3.08 rearends
Well then I'm happy if thats correct.
Then first gear wouldn't be soo short...
11-05-2003, 01:26:00 AM
On the spec list for my new 77 Z28 the trans was listed as a WIDE-RATIO.
Al, I really like the 2.64 trans, which is a Super T-10 U, I believe. It may be a W. Sorry, can't remember !
My '80 had the steep first gear, and it was really unuseable.
With my 454 and 3.08s the 2.64 is perfect, so I put one in. The big first gear trans is a lot weaker. Good for girlfriend cars.
One way to think about all this is to go ahead and multiply the gears to the torque, and compare different ratios to different engines. The overall torque available with a relatively stock rat and 3.08s is more than is available with a fair 350 and 3.73s, assuming both have the same trans ratios. Even with the 3.08s the big block car is thrustier off the line and through the gears. I've had 'em all the different ways over the years, and the math does work in the real world.
Another way to look at all this that hasn't really been mentioned (unless I missed somebody, sorry!) is the idea of time-in-gear.
With a short mill, one that is all in about 4500 or so, the steep first gear will let your engine run out of breath way to soon to be of any use. Steep gears need rpm. I usually win races when the other guy has to shift first, so if I'm not running an rpm engine then I run big torque and tall gears. In the end, it's always the same... who shifts first usually loses, in my experience.
Al, you sure pop up all over the board ! Cool !
11-05-2003, 05:42:00 PM
I'm a little confused. So do you think I have a 2.68 fist gear? I'm worried it might be 3.42 first in my 80Z
P.S Who cares I'll still powershift until something blows!!! LOL
11-05-2003, 06:05:00 PM
Yes- if the transmission has never been swapped out or modified- you should have the lower (numerically) first gear. Just so we're clear the Z28 "package" included the "close ratio" manual transmision- so unless someone hobbled together one whacky 'Z' (sort-of) out of RPO codes on the dealer order form- you should have the ST-10 close ratio. One thing to note as well- no '78-81 Z28 came with 3.08 rear gears unless someone specially ordered this on a production order. Of course- with GM, never say "never" -as mentioned above, some whacky 'custom' things have been seen out there- but changing specific RPO codes only on a car was a major ordeal/issue by 1980 compared to cars ordered in the early 70s before emissions restrictions came into effect.
Keep one other thing in mind- Pontiac Firebirds and Chevy Camaros did not come in the same configurations- you can find lots of '79-81 Trans Ams/Formulas with 3.08 rear gears and wide-ratio transmissions- but Camaros were their own entity with their own options/features. Don't ever assume what was true for a Firebird is the same for a Camaro.
11-05-2003, 06:27:00 PM
Thank you very much Eric...
So hopefully this tranny will last me a while.. Some mods will come in the future and I just need the scope as to whether it will tolerate extra power...
Being the 2.68 first gear relieves me of my fear of that notorious 3.42 first everyone seems to be talking about...
11-06-2003, 09:52:00 AM
Sorry to disagree, but my 80' Z (fully documented by GM of Canada) that still has the original trans and rear end, has a nodular iron cased, iron midplate, close ratio ST10, and a 3.08 geared Posi rear, also original.
According to the model information that GM sent me, the 3.08's were the standard gear for a stick sfhift car, and the iron cased ST10 was a mid year change.
I would assume that this means that the car would also have the stronger gears in the trans.
11-06-2003, 12:28:00 PM
Something's funky there Rick- either GM Canada had it's own Z28 for 1980 (possible- but not documented thus far) or the documentation they sent you is BS and someone at GM got the Pontiac's and Chevy's mixed up- I believe the 3.08 was the standard on '80-81 Transams after the discontinuation of the 400ci engine in '79.
Can you post a picture of the paperwork that states this? If there's something out there to be noted about 1980 Canadian Z's- we'd like to know about it...
11-06-2003, 03:38:00 PM
Actually I recieved my Package from General motors from a George J. Zapora (Vintage Specialist at GM). and the option code for the rear end the tranny reads:
GU4 Rear axle - 3.08 Ratio
G80 Rear axle - positraction
MM4 (4-speed manual transmission)
M21 (4-speed manual transmission-close ratio)
GM probably made a mess with accuracy with their codes but that's what it says.
These codes for the tranny are confusing... Anyone who can make heads or tales of it.. By all means let me know...
11-06-2003, 03:57:00 PM
Sounds like the only way to really know what you've got is to drop the driveline and spin the motor in 1st gear by hand. 2 person job though.
'79 Z28,White w/camel tan interior,Cowl induction hood,T-10 4SPD,350 RamJet (polished),Jet-Hot coated Hooker Headers,Magnaflow dual exhaust,11" Ram clutch,9" 370 Posi,Rock Valley fuel tank,Vette Brakes monoleaf suspension,AGR quick ratio steering,Baer 4 wheel brakes,17X9 Cragars w/275/40X17's F&R
11-06-2003, 04:27:00 PM
<font face="Arial,Verdana" size="2">Originally posted by Caesar1:
GM probably made a mess with accuracy with their codes </font>
Certainly seems that way- there shouldn't be 2 option codes for the transmission- one or the other- not both. This seems to call into question the accuracy of these Canadian "historical" packages, doesn't it?
I'd go with hotrod on this one- forget the GM package information and go check the rear out yourself to be 100% certain whats/wheres been put in there.
11-06-2003, 06:21:00 PM
You guys are right. However maybe something which leads me to believe it is not a 3.08 rearend is that my cars revs at 2700 rpm at 100kph (60mph).
Is that high for 3.08 or I'm thinking it could be highier...
I'll do what you guys mentioned...
Thanks for the feedback.
11-06-2003, 08:34:00 PM
<font face="Arial,Verdana" size="2">Originally posted by Eric:
One thing to note as well- no '78-81 Z28 came with 3.08 rear gears unless someone specially ordered this on a production order. </font>
I'm not sure what we're talking about for sure. Are you saying that no US 78-81 Z28 came with 3.08's? If that is what you are saying, then I think I'll have to disagree as well.
On the spec page for 1980 of this site, It states: "Rear Axle Ratios were 3.42 (including California) for Turbo Hydra-Matic and 3.08 for 4-speed; no options" This was a copy and paste straight from MadMike's 1980 Camaro Data. Further down the page there is a Performance article: "Z28 Performance Test Data
Source: Car & Driver - 4/80. Test Vehicle: 1980 Z28, 4 speed 3.08:1, curb weight 3660 lbs" It had a 1st gear of 3.42. This is a direct copy and past as well.
Like I said, not sure if there changes for Z-28 of that year, but by looking through the Camaro data, I sure couldn't find anything to back up what Eric says. If there is more info I am unaware of, please give me the source. By the way, please don't take this as a smart a$$ comment.
11-07-2003, 03:20:00 AM
When the very late 2nd gen cars were new you got a 3.08 gear when you got a 4-speed. There was no optional ratio ever for these cars. The number was determined by the trans choice.
To make up for the change from 3.73 to 3.08 the trans ratios were altered including the steeper 1st gear. The 2.64 cars came with the 3.73 rears while they were still being offered.
The literature that came with my 77 1/2 car when it was new clearly said that the transmission was a wide ratio.
It doesn't really matter, though, unless one is into the paperwork side of our hobby.
That was the fact of life then, that's all. Having been there at the time and having purchased 3 of these cars when they were new helps to cut thru the haze of historical uncertainty.
As for Canada, I dunno.
Stuff gets a little hazy when discussing it as history.
[This message has been edited by aero80 (edited November 07, 2003).]
11-07-2003, 11:16:00 AM
I have the same tranny you do. Well I'm pretty sure I do, if yours has 6 lines on the input shaft. But anyways ST-10s are really strong. Cast iron houseing, with a metal plate between the tail houseing and the main houseing.
And I know for a fact that T-10s and ST-10s all have a closer gear ratio. They also offer a much wider variety of gears. There are 4 different sets you can choose from, while muncies only have 3 sets. Heres a list of both trannys gear sets.
T-10 and ST-10
Input shaft 1st 2nd 3rd 4th
2 Lines 2.43 1.61 1.23 1.00
3 Lines 2.64 1.75 1.33 1.00
5 Lines 2.88 1.91 1.33 1.00
6 Lines 3.42 2.28 1.46 1.00
Input Shaft 1st 2nd 3rd 4th
No Lines 2.56 1.91 1.48 1.00
1 Line 2.20 1.64 1.28 1.00
2 Lines 2.52 1.88 1.46 1.00
Me have a 3.42 first gear is the reason why I can barely make it though a stop light on a normal shift. If I go racing shift I can make it go longer letting the engine rev higher.
Cars, Computers, and Women, my 3 favorite things. All nothing but trouble
11-07-2003, 11:45:00 AM
<font face="Arial,Verdana" size="2">Originally posted by Als78z28:
not sure if there changes for Z-28 of that year, but by looking through the Camaro data, I sure couldn't find anything to back up what Eric says. If there is more info I am unaware of, please give me the source. By the way, please don't take this as a smart a$$ comment.</font>
No -apparently it's just me- old age, bad memory and mixing up different years - http://www.nastyz28.com/ubb/smile.gif
11-09-2003, 02:18:00 PM
I am looking at my GM of Canada decode right now. Here are the codes of consequence that are listed on my option sheet.
GU4 - REAR AXLE - 3.08 RATIO
G80 - REAR AXLE - POSITRATION
MM4 - 4 SPEED MANUAL TRANSMISSION
M21 - 4 SPEED MANUAL TRANSMISSION - CLOSE RATIO
I have verified a 3.08 gear in the rear and the trans is an iron cased ST10 with 2.64 fist gear.
11-14-2003, 07:20:00 PM
Can I bolt a Big Block to this tranny?
Like a 427 would be really nice..
Can it work?
Or should I go fo a Muncie m21 m22?
I want to know if it can take a Big Block, and still be reliable. I not going to kill it everyday, but I would hope to think these ST-10's are good enough...
What do you guys think?
11-15-2003, 05:45:00 AM
Ceasar, no disrepect brother but go back and look at Aero's response. His is like the fifth or sixth response to your original post.
[This message has been edited by Zee (edited November 15, 2003).]
11-17-2003, 04:35:00 PM
No disrespect buddy!
I'm blind sometimes and have to reassure myself at times... So that is good to know. Guess I'll need a Big Block Bellhousing too.
Just as long as that thing holds I'll be happy. I'm keeping the same rearend and can't wait to start next year. I have to look for a good motor.
11-18-2003, 09:28:00 PM
Good, I thought you were all PO'd.
You should be in luck with the bellhousing as the bolt patterns are the same between the BBC and SBC. Two different bellhousings are available depending on the size of the flywheel you decide to use.
[This message has been edited by Zee (edited November 18, 2003).]
11-19-2003, 11:49:00 AM
I'll sleep well knowing I can still use this tranny and have a nice BBC 427 between the rails of my car.
I'm saving my pennies and being patient as next summer it'll be very interesting.
11-19-2003, 11:22:00 PM
I just got back from a hard run to AZ and back on Sunday, enjoyed my '54 and Supe just like the ad would'a said to, had this combo been available from the Chevy Sports Dept. when new.
I love the soft gear whine that the Supe makes when going thru the gears.
I've never, ever had a prob with my gears.
11-21-2003, 05:57:00 PM
Camaro4life18 you have the same tranny as I do...
What kind of motor do you have in your car? and have you had any problems with it? You mentioned 1st gear is a digger gear... So you would think that the ST-10 Z are pretty good?