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Auto with 3.27 gear & big tires, now torque converter slips?
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surlyguy
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PostPosted: Sat Jul 13, 2019 9:33 am    Post subject: Auto with 3.27 gear & big tires, now torque converter slips? Reply with quote

With newly upgraded transmission, and 5% bigger diameter tires, have I gone too far? At 65mph in 3rd with a headwind I'm getting a lot of slip on the torque converter resulting in too much heat in transmission. Too high of a gear now?

Suggestions? Working on a bigger cooler already.

Thanks.
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Wildthings
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PostPosted: Sat Jul 13, 2019 1:49 pm    Post subject: Re: Auto with 3.27 gear & big tires, now torque converter slips? Reply with quote

The torque converter always slips some, there is no lockup provision. Floor the engine and the rpms will always climb to 3000 or above.
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MarkWard
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PostPosted: Sun Jul 14, 2019 5:21 am    Post subject: Re: Auto with 3.27 gear & big tires, now torque converter slips? Reply with quote

What engine?
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schuetter
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PostPosted: Fri Jun 18, 2021 1:20 pm    Post subject: Re: Auto with 3.27 gear & big tires, now torque converter slips? Reply with quote

My tranny just bit the dust, so I’m considering installing the 3.27 ring/pinion from Country Homes Campers. It’s supposed to reduce highway RPM’s by 800, which would be amazing. I have the GW 2.3 and their external cooler for the tranny. Anyone here have experience with similar setup? I’m torn on whether to spend the $1600 for the R&P upgrade or just go with standard rebuild. Thanks in advance!
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skills@eurocarsplus
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PostPosted: Fri Jun 18, 2021 2:47 pm    Post subject: Re: Auto with 3.27 gear & big tires, now torque converter slips? Reply with quote

i wrestled with this too when i did my trans and subaru build

Matt Steedle who has had a V6 honda strapped to an auto box told me save my money and play with tire size, which i did.

so i went with a 27" tire (i think, would have to check)

at 65, i'm turning about 3600 rpms as i recall. i haven't beaten the thing up too much as it all just turned 100 miles old.

having said that, i'm pretty happy. from a dead stop i pulled a 9% grade at 50 and still had a lot of throttle in my pocket.

another data point.... no matter how i drive it....so far i haven't seen a trans temp above 145* and even at that it takes a good 20-25 mins to get the needle to move

play with the #'s. like Matt said....cheaper to mess with tires than a R+P if you hate it and truth is he's right
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Shonandb
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PostPosted: Fri Jun 18, 2021 9:29 pm    Post subject: Re: Auto with 3.27 gear & big tires, now torque converter slips? Reply with quote

I've been contemplating the same thing as I did the Subaru swap and have a 2.5L SOHC in my Bus. Thanks for commenting Skills, it validates what I've tried so far.

I upgraded my tires to 215/65/16 load rated and am tracking around 3600 rpms at 65 mph and just over 4000 at 75. Not ideal for gas mileage but can hold these speeds up most grades, loving the power. Think I'll hold off on the r&p upgrade for now.
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skills@eurocarsplus
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PostPosted: Fri Jun 18, 2021 10:36 pm    Post subject: Re: Auto with 3.27 gear & big tires, now torque converter slips? Reply with quote

Shonandb wrote:
I've been contemplating the same thing as I did the Subaru swap and have a 2.5L SOHC in my Bus. Thanks for commenting Skills, it validates what I've tried so far.

I upgraded my tires to 215/65/16 load rated and am tracking around 3600 rpms at 65 mph and just over 4000 at 75. Not ideal for gas mileage but can hold these speeds up most grades, loving the power. Think I'll hold off on the r&p upgrade for now.


on stock cams you're right in the sweet spot in terms of max torque:

1000 rpms = 137 lb-ft divide by 170 lb-ft = 80.6% of max torque
2000 rpms = 156.25 = 91.9%
3000 rpms = 162.5 = 95.6%
4000 rpms = 170 = 100%
5000 rpms = 164 = 96.5%
6000 rpms = 140 = 82.3%

that is for a 2.5

i think a lot of swappers don't take into consideration cruising rpms/torque curve etc no matter what platform they use. they just kinda grunt and say 'more horsepower is better'

i think vw owners put more weight into thinking about this stuff (especially van/bus owners) seeing that these were over weight under powered machines right out of the gate.

i went with 17" wheels as there seems to be a better selection of load rated tires in that size.
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gprudenciop wrote:

my reason for switching to subaru is my german car was turning chinese so i said fuck it and went japanese.......
[email protected] wrote:
most VW enthusiasts are stuck in 80's price land.

Jake Raby wrote:
Thanks for the correction. I used to be a nice guy, then I ruined it by exposing myself to the public.

Brian wrote:
Also the fact that people are agreeing with Skills, it's a turn of events for samba history
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Shonandb
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PostPosted: Fri Jun 18, 2021 11:19 pm    Post subject: Re: Auto with 3.27 gear & big tires, now torque converter slips? Reply with quote

on stock cams you're right in the sweet spot in terms of max torque:

1000 rpms = 137 lb-ft divide by 170 lb-ft = 80.6% of max torque
2000 rpms = 156.25 = 91.9%
3000 rpms = 162.5 = 95.6%
4000 rpms = 170 = 100%
5000 rpms = 164 = 96.5%
6000 rpms = 140 = 82.3%

that is for a 2.5

i think a lot of swappers don't take into consideration cruising rpms/torque curve etc no matter what platform they use. they just kinda grunt and say 'more horsepower is better'

i think vw owners put more weight into thinking about this stuff (especially van/bus owners) seeing that these were over weight under powered machines right out of the gate.

i went with 17" wheels as there seems to be a better selection of load rated tires in that size.[/quote]

Great info Skills. I've found the engine is quieter/smoother at 4000 rpms than at 3500. Maybe it's just that the outside noise increases or that I have to concentrate on the road more at 75. Very Happy
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Red Beard
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PostPosted: Tue Jun 22, 2021 9:00 am    Post subject: Re: Auto with 3.27 gear & big tires, now torque converter slips? Reply with quote

I have an auto with a 3.27, with 215 65R16 tires. I initially had this mated to the FAS Gen V turbo setup, and it was a good match from a drivability standpoint except I had to put a big radiator type trans cooler with a thermostatically switched fan due to high trans temps.

Unfortunately, due to repeated turbo issues, I decided to remove the turbo and am now basically running the FAS Gen V naturally aspirated. So basically going from something around suby 2.5 power down to bostig-level power. The 3.27 with these tires and the auto trans is now underpowered on the freeway, somewhere around stock 2.1 levels of acceleration between 55-70mph. Its a dog on the hills.

But at least I don't have to rebuild the turbo with every oil change anymore Rolling Eyes

And this is not to dis on the FAS Gen V setup or the company...they've been great working with me past the warranty period, and apparently they don't see issues like this in the many vans they've converted. Spent a lot of time on the phone and investigating and hypothesizing and bottom line is we can't figure it out.

I might try going back to a smaller tire size when these tires are ready to go, but not sure how much that will really help.
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danfromsyr
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PostPosted: Tue Jun 22, 2021 11:34 am    Post subject: Re: Auto with 3.27 gear & big tires, now torque converter slips? Reply with quote

yeah the 3.27 gears is a HUGE jump and really only suited to a chipped 1.8T or a SVX something in the 175-250hp area.

for those that think a higher R&P to lower engine RPMs will net MPG gains.. it won't MPG is based on other dynamics than RPM.. engine LOAD will still require fuel even at lower RPMs. and too small of a motor won't overcome the mpg/load threshhold.

lower RPMs will burn/consume less oil in subaru powerplants though Wink
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Red Beard
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PostPosted: Tue Jun 22, 2021 11:48 am    Post subject: Re: Auto with 3.27 gear & big tires, now torque converter slips? Reply with quote

danfromsyr wrote:


for those that think a higher R&P to lower engine RPMs will net MPG gains.. it won't MPG is based on other dynamics than RPM.. engine LOAD will still require fuel even at lower RPMs. and too small of a motor won't overcome the mpg/load threshhold.



I can confirm that, I saw no difference whatsoever.
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skills@eurocarsplus
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PostPosted: Tue Jun 22, 2021 12:25 pm    Post subject: Re: Auto with 3.27 gear & big tires, now torque converter slips? Reply with quote

i just did a trip and didn't run the numbers. van was fairly light on the way out, but freighted on the way back.

averaged about 70-75. going by what i put in the tank vs what the gauge said i burnt it's looking like around 22.5 mpg doing some rough math

75 was turning about 3900 rpms. right in my sweet spot. a few runs up to 80-85 just because i can Very Happy

i averaged about 160* trans temp. my cooler isn't huge, about the size of a phone book (remember them Laughing )

Image may have been reduced in size. Click image to view fullscreen.


no fans, no scoops...just hanging there.

what was interesting was in stop and go/around town i hit about 165-170* and all i can assume at this point is the TQ was getting a bit of heat soak (exhaust is run in about the same location as the WBX)

what was really neat was hitting a rain storm. just the mist from the road dropped the trans temp to 145*

anyway, i thought long and hard about how to approach this and it was a compromise of splitting the difference so i kept the stock gearing and messed with the tire size
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gprudenciop wrote:

my reason for switching to subaru is my german car was turning chinese so i said fuck it and went japanese.......
[email protected] wrote:
most VW enthusiasts are stuck in 80's price land.

Jake Raby wrote:
Thanks for the correction. I used to be a nice guy, then I ruined it by exposing myself to the public.

Brian wrote:
Also the fact that people are agreeing with Skills, it's a turn of events for samba history
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Wildthings
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PostPosted: Tue Jun 22, 2021 1:17 pm    Post subject: Re: Auto with 3.27 gear & big tires, now torque converter slips? Reply with quote

danfromsyr wrote:
yeah the 3.27 gears is a HUGE jump and really only suited to a chipped 1.8T or a SVX something in the 175-250hp area.

for those that think a higher R&P to lower engine RPMs will net MPG gains.. it won't MPG is based on other dynamics than RPM.. engine LOAD will still require fuel even at lower RPMs. and too small of a motor won't overcome the mpg/load threshhold.

lower RPMs will burn/consume less oil in subaru powerplants though Wink


Miles per gallon depends on many things. Engine cooling fans take less horsepower at lower RPMs and there is less crankcase windage. Also engines are more thermodynamically efficient when the manifold vacuum is (numerically) lower.

That said I have never noticed a whole lot of difference on any vehicle I have owned, including my old pickup in which I replaced the original 4sp with a 5sp in which 5th gear is a 30% over drive. I do probably drive faster now that before, but the gas mileage is close to where it was to start with.

Certainly on new cars with instantaneous gas mile mileage readout, you will see a positive jump in gas mileage in the higher gear.
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PostPosted: Fri Jun 25, 2021 8:06 am    Post subject: Re: Auto with 3.27 gear & big tires, now torque converter slips? Reply with quote

Just a quick note to add for anyone with a Late Bay who has an 003 Auto and is thinking about the r&p ratio upgrade or switching to a 010 auto. I swapped back to my original 003 auto while I'm having my 010 refreshed and noticed the following:

010 at 60mph = 3500rpms
003 at 60mph = 4000rpms

The 003 shifts more smoothly but the 010 feels more solid/capable of handling the extra Subaru HP.

I'm running 215/65/16 load rated tires for reference.
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Last edited by Shonandb on Fri Jun 25, 2021 11:21 am; edited 1 time in total
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PostPosted: Fri Jun 25, 2021 8:53 am    Post subject: Re: Auto with 3.27 gear & big tires, now torque converter slips? Reply with quote

Shonandb wrote:
Just a quick note to add for anyone with a Late Bay who has an 003 Auto and is thinking about the r&p ratio upgrade or switching to a 010 auto. I swapped back to my original 003 auto while I'm having my 010 refreshed and noticed the following:

010 at 60mph = 3500rpms
003 at 60mph = 4000rpms

The 003 shifts more smoothly but the 010 feels more solid/capable of handling the extra Subaru HP.
Interesting, thanks for sharing.... Cool Cool
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