Oldsmobile Achieva SCX 5-Speed Getrag (Page 1/3)
82-T/A [At Work] AUG 16, 02:21 PM
Ok, so... I'm planning for the restoration of my 1987 Pontiac Fiero, as soon as my daughter's car is out of the garage.

As I'm writing this, there are two minutes left on an auction where I'll essentially be buying an Oldsmobile Achieva W41 SCX 5-Speed Getrag.

Now, I already have 2 5-Speed Fiero Getrags... one that has super low miles... like 30k, which I got from Blacktree or someone else (can't remember), and another 5-Speed Getrag which has 130k miles on it, and is seriously ragged out. The case itself though is SOLID, and everything spins.


Since I know the Olds Achieva Getrag uses a different bell-housing, can I simply swap out the bell-housing with the one from the Fiero Getrag?


For the record, I'm going to attempt to rebuild it myself, entirely (yes... I know... I can't do it, blah blah, get a professional).

I took apart my daughter's spare 5-Speed Isuzu, and that looks less complicated than rebuilding an automatic, so I think I can do it.

Any advice... do you guys know where I can get a solid rebuild kit? (new bearings, etc.)?


Last question can I literally swap out all of the Getrag stuff from the Achieva into the Fiero's transmission case? Or is that defeating the purpose of what made the W-41 Getrag special?


I know the gearing is different... from what I understand, the final drive ratio of the Olds Achieva Getrag is 3.91:1, with a better (higher rpm) 3rd and 4th gear.


Thoughts? (Keep in mind, I want to keep the car as stock looking as possible with my 3.4 swap).


Thank you!!!
... and it's mine: https://www.ebay.com/itm/305714481284
fieroguru AUG 16, 07:02 PM
That looks like a 92 transmission, so it could be one of the HTOB transmissions from 92-94. If it is, then one of the shift shaft rails will be shorter than the non-HTOB getrag.

To make room for the base of the HTOB, the case is shallower and took up some space for one of the shift rail bosses.
pmbrunelle AUG 16, 09:53 PM

quote
Originally posted by 82-T/A [At Work]:
I know the gearing is different... from what I understand, the final drive ratio of the Olds Achieva Getrag is 3.91:1, with a better (higher rpm) 3rd and 4th gear.


Thoughts? (Keep in mind, I want to keep the car as stock looking as possible with my 3.4 swap).



Gearing-wise, it's kind of like the 84 M19 4.10 Performance transmission, so if you liked that, then I think you'll like the SCX gearing.
Raydar AUG 20, 06:13 PM
I've got a "converted" Quad 4 Getrag in my GT. I also have a spare of the identical trans. (I think the code is FDDC or something like that. Info that I've found indicates that it may have come from a European minivan application.)
The un-converted spare is, indeed, the HTOB version.
I really like how it feels, bolted to a 2.8. The gear spacing just seems... "right".

To directly address your question, I have never taken a Getrag apart (other than the really tired one that I blew up, leaving a club meeting.)
But I understand they require a number of specialized tools, jigs, and other things.
Be careful, and good luck.
fieroguru AUG 20, 08:09 PM

quote
Originally posted by Raydar:
To directly address your question, I have never taken a Getrag apart (other than the really tired one that I blew up, leaving a club meeting.)
But I understand they require a number of specialized tools, jigs, and other things.



Taking them apart is pretty easy... setting the bearing preload on assembly is the critical step for longevity.
Raydar AUG 20, 09:18 PM

quote
Originally posted by fieroguru:


Taking them apart is pretty easy... setting the bearing preload on assembly is the critical step for longevity.



Ah. Okay.
I was (I think) thinking about removing/reinstalling various shafts, full of gears. But yeah. I suppose that setting the bearing preload is a bit daunting if you've never done it. Which I haven't.

[This message has been edited by Raydar (edited 08-20-2024).]

82-T/A [At Work] AUG 23, 07:59 AM
Thanks guys, I appreciate it. Sorry I didn't respond earlier, I was away on business.

I have three Getrags total... one which has 30 some odd k which I don't want to mess with, but a rather tired and worn out one, which I want to essentially use with this SCX one to make the "ideal" Fiero Getrag I suppose.


You guys mentioned about it feeling like a 4.10:1... I know the difference is essentially a .3 in the final drive. It's a 5-Speed of course, so will I still be able to drive on the highway and not have my engine screaming if I'm cruising at 70 miles an hour? What would the RPM be, effectively, at 70 miles an hour?

Anyone know where I can buy a proper rebuild kit, or is there a Getrag manual?
Thanks guys!
pmbrunelle AUG 23, 11:41 AM
There are two gear reductions in a transaxle like the Fiero uses.

The first reduction (or overdrive) is in the speed gear.

The second reduction is in the final drive, and applies to all speed gears.

You should calculate the total reduction (which is the product of both ratios) if you want to make meaningful comparisons between different transaxles.

Example of total reduction calculation for M19 Muncie:

2nd speed gear ratio = 1.95
Final drive ratio = 4.10

Total reduction in 2nd gear = 1.95 * 4.10 = 8.00

Tabulate this information for all gears for the transaxle alternatives you are considering, then you should be able to better compare things.
Raydar AUG 23, 03:19 PM

quote
Originally posted by 82-T/A [At Work]:
...What would the RPM be, effectively, at 70 miles an hour?




2948 RPM. Check your PMs.
82-T/A [At Work] AUG 24, 10:40 PM

quote
Originally posted by Raydar:

2948 RPM. Check your PMs.




Thanks Radar! I appreciate it.

Do these RPMs seem reasonable for highway driving? I'm just curious because I seem to recall in cars like my Crown Victoria, which only has a 4-Speed automatic... at ~65, it's basically barely pulling 1,500 rpms with a 2.73:1 final drive. So ~3,000 rpms seems a bit aggressive. I'm just wondering if that's significantly more than what would be reasonable... hah...



quote
Originally posted by pmbrunelle:

There are two gear reductions in a transaxle like the Fiero uses.

The first reduction (or overdrive) is in the speed gear.

The second reduction is in the final drive, and applies to all speed gears.

You should calculate the total reduction (which is the product of both ratios) if you want to make meaningful comparisons between different transaxles.

Example of total reduction calculation for M19 Muncie:

2nd speed gear ratio = 1.95
Final drive ratio = 4.10

Total reduction in 2nd gear = 1.95 * 4.10 = 8.00

Tabulate this information for all gears for the transaxle alternatives you are considering, then you should be able to better compare things.



RGR, thank you! This makes perfect sense. I always wondered exactly how the individual gears vs. the final drive gearing worked.


Thanks!