84 Olds Transmission Identification

[84ZZ4]

84 Oldsmobile, 2bbl 3.8L 3 speed auto with lockup.

I've talked to five people who've SWORN it has to be a TH200C... but the pan doesn't say ANYTHING on it, and the tranny SOUNDS like a TH350.

Did they put TH350C in these cars behind the 3.8L? Is there any way to tell for sure?

 

[83build-up]

what does a th350 sound like?it prob. is a th200.there was no need to put a th350 behind a 2-barrel V-6 unless it was a turbo.

 

[78Buick]

I Have a TH350

I have a TH350 in my '78 Regal and it's behind a n/a 3.8 (for now anyway). The 200 & 350 have different pan shapes. Get on gnttype.org and look at the photo guides. That should tell you what you you have.

 

[84ZZ4]

The gnttype site wasn't a lot of help. I already know I don't have a 200-4R. Everything I've seen says the pan shape is identical between the TH350 and TH200.

As far as what a TH350 "sounds" like, they have a very distinct (to me) noise the make at high RPM in 1st gear and when they downshift to 1st when coming to a stop. No other tranny I've ever driven has sounded quite like it--although granted, I've never driven a car with a TH400 either.

I did just look at a website that showed a different pan shape for the TH200, and mine still looks like a TH350. Maybe Oldsmobile stuck with the 350 because they still offered a V8.

 

[b4black]

Going from my vauge memory about this....The 200 has an external band adjustment or something like that, that can be seen on the side of the case. The 350 doesn't have it.

I'll move this to the transmission forum. I'm sure soembody there has better information.

www.montecarloss.com may be another good resource for this. They have plenty of links to tech pages.

 

[b4black]

Wait, try this.

On the SPID sticker under the decklid

MV9 = 200
M31 = 250
MX2 = 350

I don't think the 350 was offered behind a 3.8 2bbl.

 

[MeanBuicks]

Easy solution.

Look at the rear of your transmission. Is the tail section of the case removeable?

The TH-350 has a separate tailhousing fastened to the case with four bolts and the TH-200 does not have a removeable tailhousing. The case is one-piece like the 200-4R.

 

[WE4]

They are mixing up 250c with a 350.
The 250c has a band adjustment for second gear. The 350 and 200 do not. Like Greg said removable or not. Then if removable band nut or not. Simple process.

 

[78Buick]

The TH350 was obviously offered behind a 3.8 2bbl because there's one in my '78 Regal. I know it's original because I'm the second owner, and the first owner was an old woman who bought the car new.

 

[85_SS]

http://www.monte-list.nu/tech/trannyid.shtml


The above link should help you ID it by looking at it.

 

[84ZZ4]

Thanks for the SPID information! That will at least tell me if the trans was originally a TH350C. I'll check the tailshaft housing, that's probably the EASIEST way to check. I assume the removable part on a TH350 bolts on similar to the tailshaft of a 700R4.

 

[84ZZ4]

Well, I apologize for taking so long, but the tranny is a TH250C. Now, what the heck can someone tell me about a TH250C?

 

[WE4]

Burn it!!!

 

[MeanBuicks]

Originally posted by WE4
Burn it!!!

He! He! We've got one running low 10's in an NHRA stocker.

As a street transmission, though, it'll be difficult to make it work well. Good TH-350s aren't expensive or hard to find. Go that route before trying to fiddle with the 250.

 

[WE4]

But you did laugh, didnt you Greg? LOL

Bruce

 

[84ZZ4]

Yes, but what exactly makes it weaker? I'm curious from an academic standpoint--it's held up fine behind the stock 2bbl 3.8 for 120k miles, which is more than a lot of TH-200s can say.

I don't really think swapping to a 4bbl carb would release enough horsies to endanger the trans, but what do I know?

 

[MeanBuicks]

The TH-250 does not have any intermediate (2nd) gear clutches like the TH-350 does. It relies soley on a relatively small band & servo to stop the direct drum from spinning during the 1-2 shift.

Under OEM conditions, like being behind an anemic powerplant, it sufficed. If you push it though, with more torque, it becomes a problem.

Bruce: Yes, I was chuckling at that comment.

 

[84ZZ4]

Well, that still doesn't tell me much. IIRC the TH350 uses a band for manual second, and it's a fairly strong trans (even in stock form).

One thing I am curious, is what speedometer gears does the TH250 use? Same as a TH350? I might be changing rear gears in the car--2.41s really are lousy gears.

Second, does anyone know if the planetary gearsets in both trannies are the same?

 

[Nordbert]

I haven't had a TH250c apart recently, but I think most of the
parts from the forward clutch drum rearward will work in a TH350.
This includes the speedometer gears and tail housing.

 

[WE4]

84zz4........ you are not listening.....

It is just not a good idea for what you want and NO IROC ever had a adjustable anything.