thm200 trans dust cover interchangeability?

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CrammerGram69

Master Mechanic
Nov 15, 2019
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Are the inspection plate/dust covers from a th350 the same as a thm200 (metric), or what about a 200r4? I didn't find much online. If i could get one I'd like it to be original GM.
 

69hurstolds

Geezer
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Jan 2, 2006
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No.

200C and 200-4R share the same cover.

TH400 and TH350 share the same cover.

But they're not interchangeable with each other according to the parts information.
 
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Rktpwrd

Builder of Cool Shjt
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Also pay attention to what engine is in front of it. Chevys have the starter cutout on the right and Oldses have them on the left.
 
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CrammerGram69

Master Mechanic
Nov 15, 2019
435
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SW, Michigan
Also pay attention to what engine is in front of it. Chevys have the starter cutout on the right and Oldses have them on the left.
I have a 231 buick.
 

CrammerGram69

Master Mechanic
Nov 15, 2019
435
143
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SW, Michigan
No.

200C and 200-4R share the same cover.

TH400 and TH350 share the same cover.

But they're not interchangeable with each other according to the parts information.
Gotcha. So the Older non-lockup metric has its own cover then? I just picked up a free trans from a friend. which has confirmed 52k on it from an ultra-mint 79 GP. Eng blew up. (301) they didn't wanna fix it.
 

69hurstolds

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Depends on the application in most instances. What kind of transmission is it?

USUALLY, the cover pans are pretty close if they are bolted behind engines with the starter on the same side as the original transmission cover starter hole, and of the same class, like Metric, or SAE from the old days. Which doesn't mean much except the use of metric fasteners or not. Exact fits? Maybe, maybe not. In your case, the transmission came out of a car behind a 301, so the transmission cover should fit, or almost fit, with most BOP engine applications. I've never done any physical comparison of covers to check for angle differences, or width/spread between bolts, etc., so although it makes sense they should be at least close, exact fits can't be guaranteed.

Be aware, some covers are metal and some are plastic. Obviously the newer the more chance it is being plastic. You can't always strictly go by part numbers either, as for example, B-bodied 307 engined cars used a different p/n cover than an A-body 260 with the same transmission for example. No real difference on why they shouldn't swap, but... I don't know what the differences are.

Good thing is with the plastic covers, a sharp knife trim here and there or a well placed drill bit can get an "almost fit" into an exact fit in short order in most instances if you don't care about originality. :)
 
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CrammerGram69

Master Mechanic
Nov 15, 2019
435
143
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SW, Michigan
Depends on the application in most instances. What kind of transmission is it?

USUALLY, the cover pans are pretty close if they are bolted behind engines with the starter on the same side as the original transmission cover starter hole, and of the same class, like Metric, or SAE from the old days. Which doesn't mean much except the use of metric fasteners or not. Exact fits? Maybe, maybe not. In your case, the transmission came out of a car behind a 301, so the transmission cover should fit, or almost fit, with most BOP engine applications. I've never done any physical comparison of covers to check for angle differences, or width/spread between bolts, etc., so although it makes sense they should be at least close, exact fits can't be guaranteed.

Be aware, some covers are metal and some are plastic. Obviously the newer the more chance it is being plastic. You can't always strictly go by part numbers either, as for example, B-bodied 307 engined cars used a different p/n cover than an A-body 260 with the same transmission for example. No real difference on why they shouldn't swap, but... I don't know what the differences are.

Good thing is with the plastic covers, a sharp knife trim here and there or a well placed drill bit can get an "almost fit" into an exact fit in short order in most instances if you don't care about originality. :)
It is a 1979 Model THM-200 Metric. Non-Lockup. My starter is on the Passenger side. I was told by a friend since the Bellhousing is a BOP it has a different valley than the chevy. If that makes sense. I don't usually get down technical with it much anymore. Any idea what the Tag says?
1650581681019.png
THM200.jpg THM200 Code.jpg
 

ELCAM

Royal Smart Person
Jun 19, 2021
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Built in 78, 13590 car down the line. Likely late 78 so 79 model year. They used PG for both years.
78 Pontiac Trans ID.png

79 Pontiac Trans ID.jpg
 
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