: TH400 questions...



Night Wolf
10-31-04, 11:00 AM
What is the average life on these?

my father told me that they were made from the factory to slip alot while shifitng gears, so that is is a smooth ride, but because of that, the life is greatly reduced, and a shift kit will fix that...

.. on the '79, she just clicked 86k last night, he fluid looks and smells clean, I have a service recipt from '84 that siad the tranny was serviced (leak fixed, adn fluid changed) at 33k ... I would guess that is the last time too...

Should I bring it to a shop and get the fluid/filter changed? if I did I would switch to Mobil 1.... also, I don't like the idea of not having an external tranny cooler.... should I spend the $50 and put one on?

most likly next year I will be moving down to Florida.... so I will drive it down there, but it will also be loaded up with stuff int he backseat and trunk etc... and depending on what happens, I need to see if the Olds is coming to FL., beucase if it is, I may rent a tow dolly and tow the Olds behind the '79.... or if I take the Olds, I may just make a 3rd trip becuase am buying a small utility trailer, and it is just 1 more load of stuff int eh car, and trailer I could take down... not sure on what is happening with that yet....

... but what I shoudl do with the tranny? just keep using it as it is? it goes into gear very nice, shifts very smooth etc.... I just don't want to have to get it rebuilt in a few years...

davesdeville
10-31-04, 05:38 PM
The TH 400 on my 78 lasted well over 170k. Then it got neutal dropped twice, hard, and the pan gasket had to be replaced, after that it was still fine - no slipping, no leaks, no noises. I think it's safe to say they're solid like undercover brother. If you're going to be doing much hard driving over distances or towing, an external cooler is a good idea, and like you said they're not all that expensive.

Night Wolf
10-31-04, 09:34 PM
neutral drop? :(

Well, I am not going to be towing the Olds anymore... today I bought a small utility trailer, I am putting a hitch on the Olds and towing it with that, so when I go to Florida, I'll make 3 trips (only like $80 to fly back up to NY).... I think between the '93 Coupe, '79 Sedan and '89 Olds with small trailer, I should get most of my stuff down...

I still want to get a tranny cooler on the '79... and the Olds since I will be towing at times (nothing extreme though) but the tranny cooler lines on that car (Olds) are rusty... ugh....

So there really isn't much to worry about with the TH400? I don't plan on hot-rodding it, but I am going to be doing some cheap and realitivly simple mods to the 425 for more power...

luddyludwick
11-01-04, 12:53 AM
Now don't quote me, but...

I think your THM400 should be fine. It is GM's "heavy duty" transmission of the time, and was behind everything from Vettes to your car, etc. They are really nice, handle a lot of power, and generally last forever.

You'd probably have more trouble if you had a THM200 or 200R4 (like my Fleet has). I know it had the "intentional slip" in it, and it was what fried the transmission eventually. The shop that rebuilt it did put in a shift kit, and it was VASTLY improved, with no loss of smoothness.

Sometimes they say it's not such a good idea to drain fluid when the transmission gets old...the fluid and metal junk floating around is supposed to hold things together!

Just be careful...a rebuild's going to cost you at least $1K! NO NEUTRAL DROPS!!!! lol...it's not like you're going to drag anyone with 2.28 gears anyhow! :)

davesdeville
11-01-04, 02:56 AM
neutral drop? :(

I'll explain. When I was swapping carbs last year, I'd just put a holley on there, and it was idled up to about 2500 rpm. It didn't seem like it was nearly that high, I guessed maybe 1200. When we put it in gear, it lurched at my friends garage door and left rubber on the driveway. I had the brakes on fairly hard, but it almost got away from me anyway. It left a pool of ATF on the driveway, but after a new pan seal it was OK.

Doesn't matter though, it's got a rod knock now. Along with its other minor problems (bad paint, bad vinyl, stapled headliner, torn back seat, fairly worn front seat, heavily worn front carpet, broken driver's and drivers side rear armrest switch panels, and broken center dash mounting pieces), I think I'll pull some parts I might need and scrap it.

Night Wolf
11-01-04, 04:21 PM
you would be surpsied how well she pulls with the 2.28... and the enigne is stock....

... I have decided to keep the stock 2.28 rear, it'll be the best for gas millage, the engine will love me ont he highway, and when I do some simple performance mods to the enigne... it'll just be more powerful then it is now... and therefor faster...

Saturday night I was on the highway... my speedo in the '79 seems to be pretty accurate....

... I was crusing about 80, but when it was clear.. I would do short blasts of speed... not even floored..... but after 85, you then go past the trip odomenter, then the trip reset, and then it is buried, but I could still see the needle if I looked down into the speedo... well, I jept going to where I coudln't see the speedo at all... I didn't even floor it either... I had to be doing almost 100mph, in 3rd gear I floored it, and it still accelerated really nice... I was definitly surprised... also the ride is very smooth, no vibration or anything.... doing 100 or so (hell crusing at 85) seemed like I was doing 70....

with the hole in the cat (drian plug removed) I could hear the enigne, and the RPM to cruise at a steady 85 wasn't high at all... it may be a 3speed auto, but with a 2.28 final drive, and moster low end torque... who needs overdrive :)

IIRC someone said my car would actually reach top speed in second gear... I don't have a tach, and wasn't ready to drop it in 2nd without really knowing the RPM.... and I would like to know what it'll top out at... I am interested now... it is just pure power pushing the car at those speeds and higher... it has the aerodynamcis of a couple bricks stacked on top of each other :)

I must say, when my enigne is running awhile and warmed up, the problem with the carb is gone and it does run very well...