What does Oppo think of - My Transmission?

"G_Body_Man: Sponsored by the number 3" (gbodyman)
05/31/2015 at 19:13 • Filed to: None

So after going through my RPO codes and cross-referencing them, I was able to establish the type of transmission that I have. I have a THM250-C mated to an LG4 305. I know the 305 is mediocre at best, but what does Oppo think of the THM250-C? Firebird for your time.

DISCUSSION (19)

west-coaster > G_Body_Man: Sponsored by the number 3
05/31/2015 at 19:31

I was around when those were in cars that were starting to get miles on them. EVERYONE who had one had troubles with it.

Typically in mid-size GM cars of the day (Malibus, Monte Carlos, Cutlasses, etc.), they were supposedly a “Chevette transmission” that was never intended to handle the torque of a V8. And I’m not talking cars in the hands of leadfoots and drag racers - just cars owned by regular folks using them for day-to-day transportation.

While GM dealers would repair them, people who were out of warranty would take them to independent transmission places, and those guys pretty much always recommended upgrading to a THM350.

G_Body_Man: Sponsored by the number 3 > west-coaster
05/31/2015 at 19:41

You must be thinking of the THM-200. The THM250-C was a THM350 without an intermediate clutch pack, and with a band adjuster. I agree that THM200s were garbage.

Tuned-Port-Injected-Rage > G_Body_Man: Sponsored by the number 3
05/31/2015 at 19:49

Its a relatively forgotten transmission, since they get a bad rep because of the earlier THM200. Its basically the same thing as a TH350 but without the intermediate clutch pack and a different adjustment band, from what I’ve heard. Since your car is after ‘79, you should also have a lockup torque converter, which is great for low-RPM cruising. It should treat you just fine so long as you don’t beat it to death or expect it to handle tons of power.

west-coaster > G_Body_Man: Sponsored by the number 3
05/31/2015 at 19:53

Oops...my bad. THM-200 was the stinker.

Never mind then. Carry on.

G_Body_Man: Sponsored by the number 3 > west-coaster
05/31/2015 at 19:55

No problem. We all have that happen to us at some point.

G_Body_Man: Sponsored by the number 3 > Tuned-Port-Injected-Rage
05/31/2015 at 19:55

So if I chirp the tires, say, twice a month, would much bad happen?

Tuned-Port-Injected-Rage > G_Body_Man: Sponsored by the number 3
05/31/2015 at 19:58

Nah, you should be just fine. Just don’t treat it like shit 100% of the time, and you should be good.

G_Body_Man: Sponsored by the number 3 > Tuned-Port-Injected-Rage
05/31/2015 at 20:02

I care about it too much to drive it hard and put it away wet, but I would enjoy putting my foot in it once in a while.

Tuned-Port-Injected-Rage > G_Body_Man: Sponsored by the number 3
05/31/2015 at 20:07

Yeah, I gotcha. Like I said, you shouldn’t have any problems with that.

G_Body_Man: Sponsored by the number 3 > Tuned-Port-Injected-Rage
05/31/2015 at 20:09

Thanks for letting me know. On a sidenote - how bad is it to have someone put motor oil in your trans?

Tuned-Port-Injected-Rage > G_Body_Man: Sponsored by the number 3
05/31/2015 at 20:18

No prob.

Uh, how’d that happen? Did it get put in place of the trans fluid or the trans oil?

G_Body_Man: Sponsored by the number 3 > Tuned-Port-Injected-Rage
05/31/2015 at 20:21

I don’t even know. On a scale of zero to invading Russia in the winter, how screwed am I?

Sweet Trav > G_Body_Man: Sponsored by the number 3
05/31/2015 at 20:22

It should hold up well behind a 305 or a very mild 350. They typically put them in cars with numerically low rear end gears, as they dont have OD.

I’d run it as is without question behind almost any 305.

If you’re looking to upgrade, I’d check and see if the Monte SS or Grand National 200-4r would bolt up in its place, or grab trans, driveshaft and rear out of one for a higher rear gear 3.73 in the monte or 3.42 in the GN. The 200-4r is probably the best 4spd auto GM made for intermediate duty. I myself am not a fan of 700-r4’s or 4l60/e’s a 4l80 is a nice transmisson, but very heavy and lots of power is just powering it.

You can build a 200-4r to handle 1000hp if you want. GN guys run them into the 9’s.

G_Body_Man: Sponsored by the number 3 > Sweet Trav
05/31/2015 at 20:27

Thanks. BTW, the PO put oil in my trans fluid. How screwed an I?

Tuned-Port-Injected-Rage > G_Body_Man: Sponsored by the number 3
05/31/2015 at 20:27

Was it just a small amount, or fully filled with it?

The reference made me lol.

G_Body_Man: Sponsored by the number 3 > Tuned-Port-Injected-Rage
05/31/2015 at 20:29

Possibly up to a quart of oil. She still runs smoothly, for some funny reason. Do I need a new trans?

Tuned-Port-Injected-Rage > G_Body_Man: Sponsored by the number 3
05/31/2015 at 20:46

If it was put where the trans fluid was supposed to go, you might just be fine. Its not great, but you can get away with it temporarily. Supposedly (and I cannot confirm this), trans fluid is just 10 weight oil with different additives in it. As long as you haven’t driven it too much, and you get the trans flushed ASAP, you should be pretty good.

Sorry for the late replys, mobile Kinja sucks.

Sweet Trav > G_Body_Man: Sponsored by the number 3
05/31/2015 at 20:51

I’d evaluate the cost of a trans flush and fill at a reputable shop vs the cost of converting to 200-4r.

In reality, unless you are utterly in love with your car, pass it off one someone else and get something else. I don’t know what you want the car to be, if you’re looking for a nice classic cruiser it may foot the bill. but its never going to be fast or “desirable” to most people, if you love the car invest the money to do it right and make it yours, if you are waivering, sell it and get something new.

G_Body_Man: Sponsored by the number 3 > Sweet Trav
05/31/2015 at 20:58

I’m not wavering. I am head over heels for my little land barge. I just couldn’t stand it being a derby car. I’ll change the fluid myself, run it until the trans grenades, and then probably put in a TH350, as it is a bolt-in swap. Thanks for the advice!