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THM125C automatic transmission coding? What final drive ratio does it have? by cebix
Started on: 07-30-2019 11:28 AM
Replies: 19 (306 views)
Last post by: cebix on 10-07-2019 02:11 PM
cebix
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Report this Post07-30-2019 11:28 AM Click Here to See the Profile for cebixSend a Private Message to cebixEdit/Delete MessageReply w/QuoteDirect Link to This Post

I'm looking to buy a used automatic transaxle and someone claims he has one with codes 6CPC and TGST on it.

I don't see any of these codes on this site: http://www.calgaryfieros.com/OSGdocs/tranny.html

Can you tell by these codes what's the final drive ratio? Is it really from a Fiero? Thanks.

[This message has been edited by cebix (edited 07-30-2019).]

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olejoedad
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Report this Post07-30-2019 08:26 PM Click Here to See the Profile for olejoedadClick Here to Email olejoedadSend a Private Message to olejoedadEdit/Delete MessageReply w/QuoteDirect Link to This Post

The code 6CPC does not appear in the NIFE Enthusiasts Guide.

The code 7CPC appears as the trans for the 87 V-6 cars.

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cebix
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Report this Post07-31-2019 02:56 AM Click Here to See the Profile for cebixSend a Private Message to cebixEdit/Delete MessageReply w/QuoteDirect Link to This Post

Do you think it's possible that this number just wasn't catalogued yet or can this transmission not be from a Fiero?

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olejoedad
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Report this Post07-31-2019 07:34 AM Click Here to See the Profile for olejoedadClick Here to Email olejoedadSend a Private Message to olejoedadEdit/Delete MessageReply w/QuoteDirect Link to This Post

I don't have info to answer that with accuracy.

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Dennis LaGrua
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Report this Post07-31-2019 11:48 AM Click Here to See the Profile for Dennis LaGruaClick Here to Email Dennis LaGruaSend a Private Message to Dennis LaGruaEdit/Delete MessageReply w/QuoteDirect Link to This Post

To check the FD ratio pull the speedometer sensor and look at the color of the gear. For instance a blue gear will be on a 3:33:1 FDR transmission, a white gear would probably be 3.18 but I've got to find the chart to give you exact numbers.

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Report this Post07-31-2019 01:37 PM Click Here to See the Profile for theogreClick Here to visit theogre's HomePageSend a Private Message to theogreEdit/Delete MessageReply w/QuoteDirect Link to This Post

Fiero trans gears listed in my Cave, Gear Ratio
Other GM vehicles often have different gearing.

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cebix
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Report this Post07-31-2019 02:10 PM Click Here to See the Profile for cebixSend a Private Message to cebixEdit/Delete MessageReply w/QuoteDirect Link to This Post

Thanks guys. I'm acting only locally with this since the shipping cost is just too much. So I'll be throwing some ideas - glad if anybody could help.

There's a TH125C near me for sale from a 1990 Grand Am 2.5. Are these a direct swap? Only readable number is 90 PNC 156364.

Thank you.

[This message has been edited by cebix (edited 07-31-2019).]

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theogre
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Report this Post07-31-2019 04:36 PM Click Here to See the Profile for theogreClick Here to visit theogre's HomePageSend a Private Message to theogreEdit/Delete MessageReply w/QuoteDirect Link to This Post

Should be same but may have a different plug etc for TCC or VSS.
Example: If new unit has Optical VSS then you have to charge most of governor to fit Fiero VSS.

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cebix
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Report this Post07-31-2019 05:08 PM Click Here to See the Profile for cebixSend a Private Message to cebixEdit/Delete MessageReply w/QuoteDirect Link to This Post

Thanks. I have some photos of said transaxle. Does it look like an optical sensor? Can you tell just by the photo should it fit the '85 2.5 Fiero?


This images is larger than 153600 bytes. Click to view.
This images is larger than 153600 bytes. Click to view.

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cebix
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Report this Post08-03-2019 05:20 AM Click Here to See the Profile for cebixSend a Private Message to cebixEdit/Delete MessageReply w/QuoteDirect Link to This Post

Bought it. Will see if it fits and works soon. Will post if it needs any modifications for future reference.

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olejoedad
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Report this Post08-03-2019 07:43 AM Click Here to See the Profile for olejoedadClick Here to Email olejoedadSend a Private Message to olejoedadEdit/Delete MessageReply w/QuoteDirect Link to This Post

It should fit, but gear ratio may be different.

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cebix
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Report this Post08-04-2019 07:56 AM Click Here to See the Profile for cebixSend a Private Message to cebixEdit/Delete MessageReply w/QuoteDirect Link to This Post

Got a better look at the transaxle and there are some differences.

The dipstick along with the tube is twice as long.
The upper vent tube is just a tube going nowhere where as in the Fiero there was a little cap there. Should I put some kind of one way valve on it or a filter?

[This message has been edited by cebix (edited 08-04-2019).]

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olejoedad
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Report this Post08-04-2019 02:57 PM Click Here to See the Profile for olejoedadClick Here to Email olejoedadSend a Private Message to olejoedadEdit/Delete MessageReply w/QuoteDirect Link to This Post

If you already have a TH125C, you should be able to use the dipstick and tube from it.

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cebix
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Report this Post08-06-2019 02:03 PM Click Here to See the Profile for cebixSend a Private Message to cebixEdit/Delete MessageReply w/QuoteDirect Link to This Post

Anybody has any ideas about these differences? I attach a photo of an original THM125C from a Fiero and the differences in my Grand Am transaxle.

1. The electrical connector is 180 degrees out of the original one. Is that a problem?
2. The cooling lines - the upper original cap is just a tube here. The lower ones where they go to the radiator - one is blocked off. What should I do about this? Is this original?

Here's an original:



And here's my Grand Am one:





Thanks.

[This message has been edited by cebix (edited 08-06-2019).]

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cebix
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Report this Post08-07-2019 03:50 AM Click Here to See the Profile for cebixSend a Private Message to cebixEdit/Delete MessageReply w/QuoteDirect Link to This Post

I found these bulletins showing the differences. Does it really matter in this situation? Can I leave the upper tube just in the air? Parts 404, 405.

Fiero:



Grand Am:

[This message has been edited by cebix (edited 08-07-2019).]

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olejoedad
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Report this Post08-07-2019 06:28 AM Click Here to See the Profile for olejoedadClick Here to Email olejoedadSend a Private Message to olejoedadEdit/Delete MessageReply w/QuoteDirect Link to This Post

The blocked off cooling line is just pinched off when it was cut.
Your Fiero cooling lines should transfer over.
The NSS (Neutral Safety Switch) and select arm will transfer over from the Fiero.
If you can change the vent tube, go for it,if not, I don't think it would be a problem.

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cebix
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Report this Post08-07-2019 07:32 AM Click Here to See the Profile for cebixSend a Private Message to cebixEdit/Delete MessageReply w/QuoteDirect Link to This Post

Unfortunately I don't have the NSS and the gear selector arm from my original transmission. Won't these found on the Grand Am transaxle bolt up to my original cable?

[This message has been edited by cebix (edited 08-07-2019).]

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olejoedad
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Report this Post08-07-2019 09:55 AM Click Here to See the Profile for olejoedadClick Here to Email olejoedadSend a Private Message to olejoedadEdit/Delete MessageReply w/QuoteDirect Link to This Post

I don't know, as I am not familiar with the way the Grand Am shifter is set up.

Perhaps someone with more knowledge will chime in.

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cebix
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Report this Post10-07-2019 07:46 AM Click Here to See the Profile for cebixSend a Private Message to cebixEdit/Delete MessageReply w/QuoteDirect Link to This Post

A little update. Cables attach good but the selector is backwards, totally messed up. D is P, N is R, R is N, P is D and you can't go forward anymore, you get the idea.

Can I somehow modify this to work correctly in the Fiero? I don't have my original gear selector arm and NSS and not sure I can buy one locally.

Thanks.

[This message has been edited by cebix (edited 10-07-2019).]

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cebix
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Report this Post10-07-2019 02:11 PM Click Here to See the Profile for cebixSend a Private Message to cebixEdit/Delete MessageReply w/QuoteDirect Link to This Post

Alternatively could anybody post some pics of their automatic transaxle near the NSS and the selector arm for reference? Would help me alot in figuring this out. Many thanks

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