Transmission diagnosed...now what?

[ShortysTRM]

Ok, since the day before I autocrossed the first time, my transmission has had some annoying recurring problems. I'm going to try to break it all down in this thread to see if anyone knows what I should do.

Transmission:
3-speed automatic in a 1993 Pontiac Grand Am GT
THM-125 aka 3t40
Controlled by throttle cable

Symptoms:

*Transmission seems to disengage for a short period of time after hard braking
*Transmission seems to disengage in a similar fashion under hard cornering
*No engine braking when manually shifted from Drive to 2nd, no forward drive without very high RPM's in manual 2nd
*Late shifts from 1-2 at a higher RPM than should be
*Loud squeal from transmission when shifted into manual 1st

Possible solutions:

It seems that these transmissions were used in many different cars, and therefore have some aftermarket support. There are high performance clutches and bands available to replace the OEM friction parts, as well as "shift kits" and torque converters.

I have bought a Haynes Techbook on my transmission, and I also own the factory service manuals for my car. My best guess from what I've read in these books, as well as from what I've learned from my road tests, it seems that my Intermediate Band is completely burnt up. I have no idea why it would be gone, since I autocross in 1st gear and have only shifted into second at Ona and at the Mercer Co. Airport event last year. When I drive the car on the street, I treat it gently. I have never been one to shift my automatic manually, either.

Obviously, one choice is to buy new clutches, bands, and whatever else I'd need to replace and just start rebuilding it. This would be very difficult, but would likely be more reliable for autocross than a junk yard replacement.

The other choice, which is my favorite, is to swap to a Getrag 282 or 284 5-speed manual transmission. The 3 speed has horribly tall gearing. My factory first gear will go to 55 MPH before it shifts, and in TCC lockup, which is similar to overdrive, I'm only just over 2000 RPM's at 70 MPH.

The Getrag 282 5-speed was used in late-80's, early-90's GM vehicles and shares the same bolt pattern and approximate size of the 3t40. There were many cars available on a similar chassis to Grand Am with this transmission, so there are factory parts that can be used in the swap. The Grand Am 5-speed console and shift linkage, the Beretta's master cylinder and hydraulic line, and some other things. My OE transmission was not electronically controlled, so that is no concern.

One big problem is the flywheel. There's no such thing as an 8-bolt flywheel from a FWD manual transmission. The V-6 5-speed F-bodies have the same crank bolt pattern, but the flywheel must be machined thinner in order to work with the 282. The vehicles that came with the 282 had a 5-bolt pattern, which would have to filled and re-drilled to work. Both would have to be rebalanced similarly to the factory flexplate.

The other big problem is that much of the drivetrain's support comes from a mount on the transmission, and a new, strong mount would have to be fabricated.

The cost of rebuilding the auto or swapping to a manual should be about the same. GM has never produced a V6 Grand Am with a manual transmission, so it has to be from another car, and could potentially lead to compatibility problems. There's a 6-speed now availble that would fit, too, but it would cost far too much and would be even more difficult to swap.


That's all I can think of for now. I have to get in place for the 10 O'clock news, so I may add to this later.

[Nathan]

The Lucus Oil trans stuff works pretty well as a quick fix. I would try to do a manual. Put the Lucus Oil stuff in and start sourcing parts for the conversion. I can't believe they don't make an aftermarket conversion for that car. That's a popular motor. Not in the Grand Am though, I guess. Seems like you know your stuff, it's way more than I do. Just do it, man. Good luck.

[Hillbilly]

Do the swap, just be sure to find out exactly how far you need to machine the flywheel and it actually sounds like it wouldn't be too bad a job to do. I'l come over and point and laugh while you're doin' it if you want.

[ShortysTRM]

That's mighty kind of you to offer, Brian lol. If I do it, and everything works right, I could actually let other people co-drive my car. As of right now, I'd be afraid that I wouldn't have any way to make it home.

I also should've included that I bought some Lucas Transmission additive in hopes that it'd help, and it seems to have done nothing at all to help. It was my last hope...

[sts 50]

Sell it and buy something cheap and light with aftermarket support.

[gtfour77]

Sell it and buy something cheap and light with aftermarket support.

That's one thought Troy... I know you like your Pontiac but in the long run I think it would be easier and cheaper just to buy a dedicated autocross car...
I know of one yellow CRX that will be for sale shortly...but there are soo many cool cars you can buy cheap nowadays. My friend Dan just bought a very nice DEl Sol Si....all for $1500... How much do you think you'll have in the trans swap? These are just ideas and you do what you think is right for you... I know you'll enjoy autocrossing in whatever car you might keep/get...;)

Plus if you'll end up getting a smaller 4 cyl import car my garage will be always open for you...;)

[ShortysTRM]

Only ricers care what country your car came from lol... And as for you, Scott, you're in the same boat as me, so you should be somewhat sympathetic lol. My car may be kinda slow, but I like it :)

You have to keep in mind that a Pontiac with a messed-up transmission is NOT going to get me enough money to afford a more dedicated autocross car. My front bumper is worth more than the car itself. As it is, I literally have no money whatsoever to put toward a different car. This isn't necessarily about autocross, it's about a car that's not running properly. I don't want a 2-seater, unless it's really worth the sacrifice. I would even be hesitant to buy a Miata, but I'm sure I would do it in the long run. We've owned this car since it was brand-new, and I don't feel like it's worth selling for a mere $1000-$2000. The engine still runs strong and makes great power, it's just never been able to put it to the pavement. I spend about 1/5-1/4 of the time on the course OUT OF GEAR, and I still manage to produce respectable times. I've known for along time that I could/should just sell it and start over on something, but it just doesn't tempt me. In terms of looks, power, comfort, etc., I'd rather have my car than a Del Sol or CRX any day. It may not have as much potential, but I have no problems with the way my car drives at the moment, aside from the transmission, obviously. My car is easy to pitch and rotate, and the modifications are still relatively few.

IIRC, my stock transmission weighs around 160 lbs., and the Getrag 282 weighs about 75. That's 85 lbs. in itself gone from a 2800 lb car. It's still not light, but it's lighter than at least 50% of the cars I run against.

If I could get April's car ready to sell, we might actually have some money to spend on a car, but I haven't the slightest clue how to safely put a car back together, and people looking at it and saying that it's pretty much junk doesn't help me at all. We understand that the car is likely to knock after we put it back together, but I at least want to be able to say that I did everything I could to fix it while I had it apart. It has been jacked up in my garage since last October.

I have no clue what the trans swap would cost me, as it is somewhat dependent on how smoothly everything works together. I have no idea how much I should expect to pay to machine a flywheel and have it balanced to match my flexplate, nor do I know where to have it done. I would trust a junkyard manual transmission far more than a junkyard automatic, and it seems like the manual may be easier, even if it didn't come that way. Of course, I'd need help to complete the job, but I'd need help buying a used car, too.

Soooooo, considering the two previous options, along with the option of just buying another 3t40 3-speed auto, I still have no idea what to do. I hope what I've said didn't sound sarcastic or inappreciative, I just want to get out as much information as possible.

[ShortysTRM]

Double the flavor, double the fun. Double post, sorry.

[Hillbilly]

After much thought I say put a junkyard replacement tranny in it and sell it. I know you'll take a loss (not to mention emotional attachment), but in the long run it will be worth it. As far as an autocross car, put a manual and a big rear bar in the subie and the problem is solved. Use the money from selling the Grand Am to buy April something dependable and you're life will be perfect;). Of course my advice is pretty much worthless, but that's the best idea I can come up with for you man.

[administerturbo]

i vote to put a junkyard/used stock transmission in it or rebuild the one you have. seems like it would be the cheapest option

[Davis K Powers]

i vote to put a junkyard/used stock transmission in it or rebuild the one you have. seems like it would be the cheapest option

amen

and Solo the sube!

[camry3sfe]

I would go with a trans rebuild rather than a junk yard trans. with the junkyard trans, you never know if that one has some problem of its own. My camry actually had the transmission rebuilt in august 2006. It cost me 1,700 dollars. probably more than my camry is worth, but I knew my engine was still very strong, and very good, which made putting the money into the car easier in my mind.

[ShortysTRM]

with the junkyard trans, you never know if that one has some problem of its own

My thoughts exactly.



Solo the sube!


Legacy GT = 3410 lbs
Grand Am GT = 2881 lbs

LGT(stock) = 165 hp @ 5600 RPMs, 166 lb.ft. @ 4000 RPMs
GAGT(stock) = 160 HP @ 5200 RPMs, 185 lb. ft. @ 2000 RPMs

LGT = 4-wheel disc brakes
GAGT = front wheel discs, read drums

LGT = AWD
GAGT = FWD

LGT = 104.3" wheelbase
GAGT = 103.4"

LGT = .85g Skidpad (est.)
GAGT = .96g Skidpad (est.)

Recalls:

LGT = 4 (+1 not listed online for some reason)
Sticking throttle return (bad for autocross)
Sticking master cylinder - may not allow brakes to release (bad for autocross)
Faulty subframe paint - may allow corrosion and susequent breakage
Faulty parking pawl - may slip out of park
Head gasket prone to failure - dealership added conditioner to coolant (not listed online, but performed at River Cities Subaru as a recall service) (bad for autocross)

GAGT = 1
Faulty ignition switch

Those are the only performance related specifications I could find for both vehicles. The skidpad data is estimated.

I like the Subaru, but I just don't feel like it's resilient enough to withstand the rigors of autocross. For clarification in this thread, let's just assume I'm wanting to keep the Grand Am as an everyday vehicle, and not as an autocross vehicle. Since none of the cars we currently own are suitable for autocross, when the time comes that I can afford to own a purpose-built autocross car, it will not be anything from our current arsenal.

[Hillbilly]

The skidpad numbers are irrelevent because of the tires used on the subie(RE92's). I know I'm biased, but I really think that racin' the Subie is the best option for someone in this position that wants to autocross. The subie will run forever as long as you don't launch it like I do and is ten times as capable an autocross car. It's just dynamically superior, it has the same suspension design as my Impreza and you see what Chris Mann's car is capable of and it's at least 50lbs. heavier than your car if it was a manual.
Just put a big rear bar on the Subie and your suspension work is done. As far as puttin' a manual in the Subie I promise I will help you if the time ever comes. Not tryin' to hurt anyone's feelings just givin' my opinion.

[ShortysTRM]

Offering to help me will definitely never hurt my feelings. :)

After putting 60,000 miles myself on the Subaru, and 75,000 on the Grand Am, I still think the Grand Am is more capable, at least as it is. The Subaru has a lot of potential, but I can't afford to get it there.

[SentraWV]

FWIW, I'm not sure anybody makes off-the-shelf dampers for Legacies. I couldn't find any when I quickly looked around (TireRack, Shox.com) when the girlfriend got hers.

[ShortysTRM]

There's not much at all available for the Legacies, and according to Boxer4Racing.com, almost nothing is cross-compatible.

[camry3sfe]

transmission rebuild will make you happy if the people rebuilding it are good, and do a good job. I think that is a good option for you, because the trans rebuild will give you a 12month/12000 mile warranty on it. So you know that your car will be working for you if you keep it. and if you want to sell it, the warranty on the trans can be a selling point for potential buyers. knowing that there is a warranty on the transmission might get someone to buy it with more confidence.

Although most people now-a-days dont like going older... getting an older car from honda or toyota might provide more reliable transportation than any GM car made from 1980-1999. Also might consider getting a Ford. The ford fusion looks nice, and offers AWD, although only in automatic. also the ford focus seems like a good compact as well. Ford really has it together for the American car manufacturers. My brother's 88 t-bird turbo coupe has had very little go wrong with it ever... Probably the second most trouble free car my family owns, just second to my camry... ;)

[ShortysTRM]

If it gets rebuilt, I'll be doing it. I'd end up paying enough to buy another car if I paid someone else to do it.


I'm still thinking very hard about doing the swap. One of the biggest setbacks is that I've never dealt with this kind of stuff before, like sourcing parts. I don't know the best way to go about it, especilly since some of the stuff I need could be easily pulled at the yard (i.e. front bumper, center console, shifter assembly) and some can't (transmission, flywheel).

Remeber, if I dod it, it's not intended to add value to the car or to make it perform better at autocross. It is for my own personal satisfaction. I have never owned a manual transmission, but I absolutely love to drive them. This is something I've wanted to do for the last 9 years, but I've never had the money, time, and a place to do it, as well as some write-ups on which parts I need and what to expect. Hopefully I don't back out of it like I do everything else.

[Jason V]

Just an FYI the tranny swap will put you in SM or XP (x prepared allowing slicks and a striped interior and alot more)... I know you are in this for fun and the class you end up in may not matter much... anyhow figure the swap will cost more than you think (it always does) and take longer to do...LOL... I personaly would go with whatever option was cheapest and easiest. Good luck with whatever you decide...

PS a crazy life kept me from attending the event Sunday... please say sorry to April for me.. I told her I would be there...

[ShortysTRM]

A few points that should be included...

The car completely skips 2nd gear during acceleration, meaning my car shifts 1-3-Torque Converter Lockup.

As I said before, the initial problem, which was disengagement under hard braking or hard cornering, started the day before I autocrossed the first time. I also changed the fluid that day, as well as the filter. I read a post about a guy with the same transmission changing filters. The new one he used had a relocated pickup, so the fluid was pulled from another spot in the pan. He said that his transmission then began doing what mine did, and that was "when [he] stopped autocrossing." This could've caused the original slipping, but I think the problem has progressed.

In both manuals I have for the car, the factory manuals and the Hayne's Techbook on my transmission, it doesn' say that this (no second gear) is a symptom of a burnt up band, but usually a problem with a servo or pin.

Also, my engine is a 3800 with shorter stroke and smaller bore. That means that if I keep the car and put in a 5-speed, the Supercharged 3800 will bolt right in when my 3300 dies :) Not that I'll ever do it, but it's an option worth another 80+ hp.

[johnnytavo]

i am not trying to be mean or anything but i just read over this thread and thought 0.96g for a grand am was a little high so i did some research and found 0.83g for a grand am gt, i would think your suby would handle much better

[ShortysTRM]

The closest number I could find for the Subaru was .85. My numbers said "estimated" because it is just that. I was able to pull .94g's on the skidpad in April's Oldsmobile Alero with no suspension mods whatsoever besides Hankook Z212's. I'm pretty sure that my car can top that.

For the record, the Grand Am has:
Falken Azenis RT-615's
Addco 1 1/8" front sway bar
Addco 1" rear sway bar
Polyurethane sway bar bushings
Front strut brace
3 degrees negative camber
TRW increased rate/progressive rate rear springs
...that may be all for suspension stuff..?


.96 is my assumption. I thought .94 seemed like a bit higher than it truly was, but I'm not going to argue.

[johnnytavo]

i thought you were referring to a stock grand am gt not yours

[ShortysTRM]

2 things...

1. I forgot to mention that the Legacy's differential has a 90/10 torque split, so it is essentially FWD. As far as I know, it is not variable like those from 2003-on.


2. If I go with the F-Body flywheel and the Beretta transmission, which clutch would I need, an F-body's or a Beretta's?

[Hillbilly]

1. The legacy's diff is 90/10 until front slip occurs at which point it delivers up to 50/50.

2. Beretta clutch for Beretta tranny.

[ShortysTRM]

1. You might be right, I dunno...

2. Thanks man.




Hey, Brian, check these out. I told you about them one night at your house. They're basically an exact replica of the Cobb EL headers, only in stainless instead of mild steel, and $307 with shipping instead of $900+. There's no cat, but a Magnaflow or DynoMax one would only run you about $50-60...if you want one, that is.
http://cgi.ebay.com/ebaymotors/OBX-Exhaust-Header-98-05-Subaru-Impreza-2-5RS-2-5L-RS_W0QQcmdZViewItemQQcategoryZ33631QQihZ007QQitemZ 170107887838QQrdZ1QQsspagenameZWDVW

[Hillbilly]

Yeah, I think I'm gonna get one eventually. In the pictures I've seen it looks like there is a high flow cat already on the extension after the collector, don't know for sure though. While I've got you on here I need your help posting pics so I can sell my Sentra chassis, I'll be in touch.