The Camaro Club (UK)

How can i find out what transmission my car has, numbers on the body or anything?
i cant work out if im having a small problem with it or if its just the way its supposed to act.

when its in top gear with what i assume should be torque converter locked, it stays engaged while the engines pulling but if i go down a slight hill (usually around 50_65 mph) the drive you can feel the drive disengage, the revs go up from around 1500 rpm to 2200 rpm and the speed drops.

then if i put my foot down slightly to make it pull again it picks up drive again and the revs drop back and it pulls the car back up to speed again.

very annoying considering the amount of motorway miles i do with bloody 50 mph speed limits on them now.

iv found if i keep it in D as opposed to D with overdrive its much happier but then at 50 mph it runs around 2200 rpm but pulls strong and the drive doesnt drop out atall.

i would much appreciate any advice on this. anyone else had this issue?

Probably a 4L60E, which was the new designation given to the old THM700

4: Speed
L: Longitudinally mounted
60: Designed for vehicles with a 6000 pounds gross weight
E: Electronic control of shifting and kickdown (No TVR cable)

Later on GM dropped the "E" as all their transmissions went electronic

If you still have the Service Parts ID label in the bottom of the glovebox it will have M30 for the 4L60E trans.
If no label the oil pan for the 4L60E is square, all the other oil pans are everything but square

As for any transmission problems, always start with the basics.
Pull the transmission dipstick and look at the fluid. If it's black and smells burned you don't need to go any further, your transmission needs to come out for overhaul.
Put the car on a level surface, get it up to normal operating temperature (fans cycling) and check the fluid level.

Electronic transmission torque convertors can be a real bugger to diagnose because they have so many inputs.
For it to lock up the following have to be met (There are probably more):

Engine at operating temperature.
In 3rd gear.
Speed over 35MPH (or thereabouts)
MAP or MAF showing a steady cruising speed.
TPS steady and withing a set (programmed) range.
No knock sensor signal.
Brake pedal off.


So a fault in any of those sensors or switches can cause the convertor to lock and unlock at the most awkward moments.

The good news, any transmission problems will store an error code, just have to get it scanned.

http://chevythunder.com/199295_lt1_trouble_codes.htm

hmm well iv checked the fluid and its a tiny bit above the max...but not enough to be a problem i would think (about 3ml)
the fluid is quite clean and doesnt smell burnt or much different to new fluid in a bottle.
i have been driving on some faster roads lately and i have noticed that at around 80-85 mph it runs about 2500 rpm but if i just give it a tiny bit more gas i feel it jump like the torque converter is unlocking the revs go to 2800rpm and the speed drops back to around 70mpg but the revs creep upto around 3000 rpm.
really does feel like torque converters slipping to me
i drove it hard for a short distance last night and the gearbox almost responds better to harder driving than gentle driving.
the gear changes are more positive and the torque converter seems to lock harder rather than just spinning away when under gentle acceleration.

Could it be dirty filters? incorrect fluid maybe?
havnt had the car long and i havnt changed the fluid yet

iv never liked automatics lol

To be honest, it could be anything, so first step is top get it scanned, it will save you a lot of money in the long run by diagnosing the problem rather than guessing what it is.

Where are you based Lucas? I have a friend in Chesham who is very good with 700r4's and 350's if it's not too far from you
Another point I just remembered is there is a procedure for checking transmission fluid levels, something like engine running and go into first then reverse to fill the torque converter before checking the level, I'm sure someone on here will k ow how to advise you correctly

_________________
1997 30th Anniversary SS SLP
1993 GMC Typhoon

yeah i did wonder about the scanning thing problem is getting the right diagnostic tools, i have some friends who have OBD2 stuff but my car is 1 of the oddball ones with an OBD1 sticker under the bonnet and an OBD2 port, so i cant even bridge the terminals like you would with an OBD1 to get the check engine light to flash any codes out

unless i can use my own OBD2 plug and download some OBD1 software that will work with it? i kinda doubt that would though.
im in nottingham myself so chesham is a couple of hours and about 120 miles away from me i think.
rather annoyingly i head down that way often but in my work car

Old and simplistic, yes. But an excellent lesson on the operating principles of the torque convertor. Knowing how it works should make any diagnosis far easier

thats an awseome video! they spent months at college teaching us how torque converters worked and still wasnt as clear as this. if only things were kept simple all the time.

anyway i might have figured something else out on my problem........

i have noticed that if i drive the car in D not D+ so it only uses 1,2,3 when its in third the torque converter seems to lock on and it feels like it makes a perfect connection even giving a degree of engine breaking on downhill stretches.
running about 2200rpm to do 50mph with non of the feeling of loss of drive like what happens if i let it use top gear.

is it possible that 4th gear can be slipping somehow? sometimes if i leave it in D+ i can be doing around 40mph at 2500rpm.

unless iv made it kickdown and stay in a lower gear that is