PFF - Pennock's Fiero Forum, PDA Edition

Ecotec turbo swap transmission options question (Page 2/4)

Will

NOV 18, 08:52 AM

quote

Originally posted by SteveMushynsky:

The F23 is rated by GM for at least 170 lb-ft torque. With the LHU and LTG producing up to 295 lb-ft torque, the F23 looks to me to be inviting eventual problems.

If that rating were gospel, the Fiero community would not have been able to run Muncies and Getrags with V8's for years. Yes, the failure rate is higher than with the original engines, but it's not like they blow up the first time you go to WOT. I've run my Getrag into the 12's with 300 RWHP Northstar. I broke a Fiero inner CV joint due to wheel hop from worn suspension bushings, but not the transmission.

The "rating" is just the biggest number for which GM has ever used the transmission. That's all it is. Don't get wrapped around the axle with regard to that.

The Fiero driveline's weak spots are: 1. Outer CV joints; 2. Inner CV joints; 3. Getrag right differential bearing boss.

The Getrag's weakness is the right side of the differential case. Some failures have split the case and pushed that boss out due to axial loading from the helix angle on the ring & pinion mesh.
The F23 case is clearly and obviously reinforced far and away above what the Getrag's case is... and yet the "rating" is the same.

I'm sure someone can link the build thread, but there's a member here who's run an F23 to the drag strip near/above 500 HP with a turbo 3800.

Since I'm building a V6/3.63 F23, I can assemble the leftover parts into an Ecotec/3.94 transmission and sell you that.

SteveMushynsky

NOV 18, 07:09 PM

quote

Originally posted by Will:
If that rating were gospel ...
... Yes, the failure rate is higher than with the original engines, but it's not like they blow up the first time you go to WOT ...
... The "rating" is just the biggest number for which GM has ever used the transmission.

Thank you for your comments, Will.

From an engineering point of view, GM's transmission ratings of "At least XXX ft-lbs torque" would be defined as the most anticipated, but not the maximum, load the unit is certified (warranted) to in its normally anticipated use environment, with a sizable safety margin included.

Ratings for a device like a transmission reflect constant-motion wear / reliability, sudden shock stress capacity, among other factors such as installation with a dual-mass or solid flywheel or electronic shifting-torque shock mediation measures.

This is why I said I felt confident that the F35, rated at somewhat less than the torque output of an Ecotec LHU / LTG, would be adequate for regular road use in a Fiero, which is 500-800 lbs lighter than the Cobalt the F40 was used in. Not so much so for the F23, despite anecdotes about its occasional use outside of its designed-for environment. My aim is to create a long-term reliable daily driver with 'guts'.

Please, no more advocacy replies from fans of the venerable F23. I'm past that decision point.

My questions are regarding installation of an F35 transmission into a pre-1988 cradle.
Specifically at this point regarding how to accomplish shifting linkages in what is now a 1984 4-speed Fiero.
Thanks.

------------------
Steve Mushynsky

1984 Fiero 2M4
34K miles

1986 Fiero SE I4 (donor now)
Lots of good miles. One very bad mile.

1987 Fiero
Tried to kill me (gone to a 'better place')
Prior owner failed to tighten a bolt. Trailing arm separated at 70 mph

wftb

NOV 18, 08:01 PM

In that case I am pretty sure you want the F35 from a supercharged Cobalt SS. The turbocharged Cobalt SS as stated before has axles that have the wrong splines to fit Fiero hubs. In addition to that the axle shafts are a larger diameter so I am pretty sure that they will not fit the earlier jack shaft found on a supercharged Cobalt SS.

------------------
86 GT built 2.2 ecotec turbo
rear SLA suspension
QA1 coilovers on tube arms

ennored

NOV 20, 12:06 PM

Also note that the LTG has a different bellhousing than the LHU (LOTS of other differences too). Only trans that will bolt right to an LTG is the F40 (from a Regal with the LTG).

(You mention the LHU/LTG torque. Not sure if you're actually considering an LTG or not...)

[This message has been edited by ennored (edited 11-20-2019).]

SteveMushynsky

NOV 20, 04:20 PM

quote

Originally posted by wftb:
In that case I am pretty sure you want the F35 from a supercharged Cobalt SS. The turbocharged Cobalt SS as stated before has axles that have the wrong splines to fit Fiero hubs. In addition to that the axle shafts are a larger diameter, so I am pretty sure that they will not fit the earlier jack shaft found on a supercharged Cobalt SS.

Thanks again for your reply. I do value your inputs.

This reinforces what I understand to be the case.

SteveMushynsky

NOV 20, 06:29 PM

quote

Originally posted by ennored:
Also note that the LTG has a different bellhousing than the LHU (LOTS of other differences too). Only trans that will bolt right to an LTG is the F40 (from a Regal with the LTG).
(You mention the LHU/LTG torque. Not sure if you're actually considering an LTG or not...)

Thank you, ennored.

Yes, I was considering the LTG as well as the LHU as they seem to get about the same price on the used engines markets. Not so many people are looking for the limited-use LHU while the LTG's price is depressed by there being so many of them about, I assume.

I understand that the LTG is an evolution of the Ecotec line with GM having said that there is almost nothing in common with previous Ecotech versions.

I see enough references online that the LTG has a different mounting pattern and different starter placement that the LTG is off my preference/selection list. Thanks much for pointing this out.

So, LHU it will be

[This message has been edited by SteveMushynsky (edited 11-20-2019).]

4thfiero

NOV 21, 10:30 AM

I have a 2007 2.4 le5 ecotec Turbo, in a 1988 Fiero GT with around 400 wheel HP. I use the F23 tranny with a Quaife LSD installed. I wa slooking into the f35 vs the f23 and the f23 won for me. The f23 are WAY cheaper and easier to find, and they were built stronger it seems. The f35's had a lot of issues and didnt seem to hold power as much as they claimed. ZZP performance also has custom flywheels that fit on the f23 to install f35 clutches as well to hold more hp. Myself and other ecotec uses (custom cobalts) with 600 plus hp use the F23 tranny bcc we prefer the gear ratio, reliability and price of the tranny. The swap is also easy.

I have been driving with this tranny for years now and ive never had an issue with it. Its a solid tranny.

Will

NOV 21, 11:52 AM

quote

Originally posted by SteveMushynsky:

Please, no more advocacy replies from fans of the venerable F23. I'm past that decision point.

Well... you certainly won't be the first person to do something the hard way when there's an easier way right next to it.

SteveMushynsky

NOV 21, 02:11 PM

quote

Originally posted by SteveMushynsky:
Please, no more advocacy replies from fans of the venerable F23. I'm past that decision point.

quote

Well... you certainly won't be the first person to do something the hard way when there's an easier way right next to it.

Thanks, Will.
I have witnessed your advocacy on this on various other threads as well. Your loyalty to the F23 is admirable. I actually do value your input. Snarkiness not really required, though. (No offense taken)

I see on SAAB forums concern about F23's and questions about transferring "stronger" F35 internals into their cases for use in their vehicles. I've also seen posts stating that choice of transmission fluid used is paramount re performance and reliability and also absolute warnings not to use additives in same. There seems to more involved in the overall F23 vs F35 reputation dispute than justifies a simple single, emphatic answer.

I won't be thrashing this transmission all that much, actually. I'm in this to learn, not to leave flaming tracks on the road. Let's see how this works out, shall we?

SteveMushynsky

NOV 21, 02:19 PM

quote

Originally posted by 4thfiero:
... I use the F23 tranny with a Quaife LSD installed. I was looking into the f35 vs the f23 and the f23 won for me ... I have been driving with this tranny for years now and I've never had an issue with it. It's a solid tranny.

Thank you for relating your choice and experience. Duly noted.