F40 vs F35

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Orion24

Member
Hey everyone, soon to be purchaser of a kit here as I already have my donor car, new engine etc….

I have been sorting out what parts to get, what direction to go and I stumbled across the infamous dilemma of going f40 or staying f35. Below I’ll go through what I discovered, my opinions and really an Avenue for feedback and correct by you guys. The ultimate goal was a transmission that will survive 400whp (not abusive). Had peace of mind.

F35: obviously 5 speed obviously not as strong as F40… there for I would budget in a rebuild and strengthen which the B3 design budget build is 2800 plus 300 for lcd model so 3100. Add 1150 for a clutch and flywheel combo and we are at 4250 buckets minus small parts.

F40: this is where I ran into a cross roads…. There are two companies that make conversion kits (Zzp and Ottp).

zzp: this kit would require me to source my own f40 so let’s say (750-850 plus 150 shipping so let’s call it ah even 1000). Plus there kit with upgraded axles is 3300. This kit used a jack shaft speed sensor, comes with a stock shifter and upgraded mounts but does include the stage 5 clutch and aluminum flywheel. So we are sitting at 4300 for parts etc. then I would need to add a 1300 dollar lsd and either install myself or pay to have it install so we are now at 5600… again minus small parts (bolts etc).

ottp: this kit includes a new regal f40, reworked speed sensor so no jack ring speed sensor, new fabricated shifter, new shifter handle and an installed lsd with upgraded mounts for 4170. I would then need to add a clutch and flywheel combo for about 1050 so we are now at 5230 for parts minus small stuff etc…

question is which kit? Pro cons of each or is this new info… im
Ready to order either and just wonder which seems easier… I’m leaning towards ottp cause I receive the transmission already done and ready to install…
 
Ross

Ross

Goblin Guru
Justin Reed (600+ hp, lots of track time) is moving from the F35 to the F23 transmission. The Goblin doesn't weigh much, and isn't as hard on the transmission as the Cobalt was. Plus the F23 are cheap, and readily available in the auto recycler yards.

My 2 cents: Just build it, try it, test it. Keep the stock F35, then decide if you need more (F40).... or less (F23).
 
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Orion24

Member
I thought about the f23 and that route as well… it seems a good way to go although I don’t see anyone that can build them but at there cheap cost I can have 100 for the price of a built f35.
I didn’t include the cost of df to adjust frame cause both the ottp kit and the zzp kit require it…
Good info thanks
 
escapepilot

escapepilot

Goblin Guru
Is going to the F23 from the F35 a direct bolt-in swap or is there much more involved? Is there a thread mentioning pros/cons of that swap?
 
O

Orion24

Member
I have been doing a bit of research…. It’s a pretty direct bolt in… you can use an f35 clutch and flywheel… and depending on your hubs you can run f23 axles or grand am axles. Trying to find the best way to source an f23… there’s basically a few build paths.

1. source a brand new F 23 depending upon gear ratio. Install either the LSD insert the quaife lsd or the cheaper knock offs…. This would be about 770 for the trans 1030 for the lsd 600 for clutch (stage 4) and 250 for flywheel. So total of 2650.

2. Cheaper Method would be source an F 23 transmission from a local you pull it place for about 160 bucks install one of the three LSD options and run either the same or cheaper clutch.
 
Rauq

Rauq

Goblin Guru
Decent conversation here and also on @OptimizePrime 's build thread

Long and short of it, the F23 is a bit stronger, has more evenly spaced gear ratios, a few more final drive options, and is much more common/available and cheaper. They have different mounts and one of the shifter arms on the transmission requires a bit of clearancing to clear the tube frame. According to OptimizePrime the SS clutch hydraulics will swap over with a bit of massaging on the lines. I'm not clear on the shifter cables but apparently the SS-length cables work well enough. LNF builds require Grand Am axles, but SS/SC builds can use base model axles.
 
Desert Sasqwatch

Desert Sasqwatch

Goblin Guru
There is a lot of information floating around on forums, this one and others, about which transmission is better than another for the Goblin. Each one has its good points and bad points, but it comes down to what a builders preferences are - weighing cost over available over ease/complexity to work on it over...well, you get the picture. ;)

I've pulled the Dr. WIKI info for each transmission to compare with the internet claims of power/gears/how-many-I-can-buy-for-$$$ superiority. Everyone has their preference. I don't need to add my 2 cents to this discussion, as my $20 worth has already been said. :cool:

GM transverse transmission facts:



 
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O

Orion24

Member
I saw you were going with the f40 option and realistically it seems fun….. budget breakdown if I’m not missing anything is basically about a 2650 for a solid f23 (minus incidental parts)

and about 5000-7500 for the f40 (depending on lsd axles, shifter etc
 
Desert Sasqwatch

Desert Sasqwatch

Goblin Guru
My costs for choosing the F40:
$750 new Regal MU3 transmission
$1000 new Quaif Opel-Vauxhall LSD
$200 F40 LSD installation kit
$250 new Saab 6 speed shifter
Stock SS/TC axles fit without modification, but new Saab 9-5 axles are $300 per pair
$2500 DF F40 frame modification
Total of $5000 - and worth every penny to me for peace of mind and a 100% new drivetrain. :cool:
 
O

Orion24

Member
What clutch did you go with and was it included?
The 2650 price tag for the f23 was with all new parts including clutch/flywheel but I’m still torn so interested in your price breakdown and opinion…
 
Desert Sasqwatch

Desert Sasqwatch

Goblin Guru
Good point, forgot that:
New Regal dual mass flywheel and clutch/pressure plate. Good for 275HP in a 3900lb car - will easily handle 350HP in a Goblin. $450
 
O

Orion24

Member
I just wish there was a way to start off with an f23 and move up to an f40 if desired but with the needed chassis mod it’s one or the other….
 
Desert Sasqwatch

Desert Sasqwatch

Goblin Guru
The F23 or F35 will fit in a F40 modded chassis, but would need an engineered and fabricated driver's side transmission mount. Basically a cross between the F40 and F35 mount. Otherwise everything else should line up.
 
O

Orion24

Member
So just to update: I actually ordered an f40 through OTTP. This way the trans comes with the lsd installed and machined for the internal speed sensor along with adjusted upgraded axles…. Guess I’m locked in for the f40 sauce
 
Desert Sasqwatch

Desert Sasqwatch

Goblin Guru
Get with Adam before placing your order to confirm your frame will get the F40 modification. They have an altered jig set up for it. Looking at the frame, unless you know it is modified, the average person wouldn't be able to see the difference. But the extra frame rail spacing and trans hard mount for the F40 make it work.
 
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Orion24

Member
X4 confirmed it’s a $2500 add on but I don’t mind… I’m kinda waiting to place my order till I can get the new shifter they are in R&d with.
 
Desert Sasqwatch

Desert Sasqwatch

Goblin Guru
Keep in mind the 6 speed shifter has 4 positions for the transmission gate selection that activate 1-2, 3-4, 5-6, and reverse. I made a basic query to Lonny about 6 speed compatibility, but didn't dig into it too far. I do have a new Saab 6 speed shifter, but not sure if I will be using it or looking at another option. ;)
 
O

Orion24

Member
Yeah he mentioned in his post about it into “banging 6th” so I’m hoping it’s compatible. If not ill order a regular shifter and fabricate some bracing for it
 
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