I am considering buying speedster with 4:12 transmission. I understand that it will rev at higher RPM, although it is a minimal difference when the math is done. I will mostly be using this car around the city in Phoenix, with little 5-10 mile highway runs. What are your feelings on this tranny v. the other.
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If the car has a smaller motor (less than 2 liters), given the driving conditions you describe (mostly city driving), then the 4.12 ring and pinioned transaxle will be perfect. The 3.88 works best with bigger motors and lots of highway driving. Al
If its a new build - I'd just go with a 3.88 (with the normal beef up mods) since it isn't much more $ than a good rebuilt 4.125. Also depends somewhat on engine horsepower/displacement and tire size. Go with small diameter tires and a 3.88 will perform just like the 4.12.
My advice is drive it with the 4.12 and see how you like it (or not). My speedster on Phx/Scottsdale highways experience was that the car needed a transaxle makeover (ie, everything passed me unless I rev'ed up close to about 4K to match the 75-80 mph traffic pace .... my engine is a mild 2.2L type 1). My madeover car is still in the shop so not sure the result, but recommend you consider the trade off between transaxle gearing and engine temp, especially if your's will be an air-cooled ride (there are a few interesting discourses on the subject on this site) in view of our warmer-than-normal AZ temperatures. Best of luck and let us know how you make out!
If you stay with your plan and do most of your driving around town you should be okay. If you start to do more highway driving you may not be happy with the 4.12.
Do you know the tire size?
Steve- If you buy this car, as people have said- drive it first, have some fun and see if you like it. After putting some time on it, if you think the gearing could use some tweaking, then we can discuss what's right for you, as there are options (they just cost money...). The difference in rpms (on the highway) between the 2 r&p's isn't huge (4 1/2- 5mph at 3500rpm with a .89 4th gear- just over 74mph vs just under 70). A taller rear tire would also do the same for way cheaper than a trans rebuild with buying gears...Al
Tires are 185/65/R15. Any thoughts?
Steve, I understand geting a second opinion (third, fourth etc etc) but the math still works out the same. In our messages back and forth, I estimated that you had 185 tires so at 60 MPH with a 4.12 R/P and.89 4th gear, you're turning 3022 RPM's. With a 3.88 R/P and .89 4th at 60 MPH your turning 2846 RPM's a differnce of 176 RPM's. Looking at it another way, with the 4.12 and .89 at 3,022 RPM your speed is 60 MPH and with a 3.88 and .89 at 3,022 RPM's your speed is 63 MPH.
Like I said and as have others, if the car is what you want, then don't sweat the gearing. As alluded to above, the slower the engine turns and the faster you're traveling, the less cooling you'll get to the engine. If city driving is the norm and and occasional jaunt of the freeway then you will be fine with the 4.12 R/P as the engine is turing a few more RPM's and thus more air flow across the cylinders/heads.
Thank you to everyone. I will be finalizing purchase this weekend. Hopefully, after all my questions, I will still be welcomed to the madness!!!
Do you know what it has for a motor? Any specs? How high does it rev with power?
and dont for get the .93 4th with the 3.88, and the .82 with the 3.88 gear. there are many diferent 4th gears to choose from and witch one is in the trans you have &the one you might get...well you may need to do a little more searching&researching to find out just what is in what? and relying on the trans case numbers dosent usualy work with these cars any more.I pulled a trans out of a 72 super that was all orignal and bought in this small town new,nothing about this rusted supre said performance or any thing at all had been done to it. well I checked the #'s and it was what I wanted, but when I puled the side cover to have a look&change the seals ....it has a super diff,4.12 gear,different 3rd gear ratio,diferent input shaft,diferent throwout bearing&shaft.it all looked new,no wear,clean nice gearlube,single sided case.and the car had been sitting for about 15 years or more.Im tickled with the trans but ....was hoping for the 388 gear.I reckon it's about time I started rebuilding vw trans. I have 2 3.88 geared trans with 2 different 4th ratios.hopefuly 1 is the .82 gear thats hard to find.Ive read it came in some KG's & somethings.1 trans is a KG trans.(by the #s')
so do some figuring & figure out whats what&what will you need. if you do a lot of 1~3 gear driving &4th mostly for highway and you have a other than stock engine(85 hp or more) than the .82 4th with the 4.12 might be a nice way to go, but there will be a nice drop from 3rd to 4th. if over 100 hp 3.88 should be just fine with the .89 4th or the .82.
look at the charts for the size tires you have ,if you can go up on tire size that is another alternative to a trans change.Im running 235/75/15 on my bug now with 4.12 trans pretty good all around combo.but I would rather have the 3.88 for the highway.(and it's stronger)
Mark- I was under the impression that the .82 4th came out of certain buses. Al
Going up in tire size doesn't make a really big difference, unless you go REALLY big.
Example:
3.88 with a 0.89 and 24.5" tire (185/65-15) will give you 2843 rpm @ 60 mph
3.88 with a 0.89 and 25.5" tire (205/65-15) will give you 2731 rpm @ 60 mph. A whopping decrease of 112 rpm.
