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djkeev
Samba Moderator
Joined: September 30, 2007
Posts: 32648
Location: Reading Pennsylvania
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 Posted: Sat Mar 23, 2024 9:58 am Post subject: Automatic Transmission, RPM vs MPH |
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I just rebuilt my automatic transmission.
It all seems to be working well except the RPM's seem high for the MPH.
I'm talking flat surface and calm winds just keep rolling at a given speed.
At 55 mph I'm spinning at 3500 rpm
At 60 mph 3700 rpm
At 65 mph 3900 rpm
I was freaked out by this so was asking dbaron what he is running on his 2.1 Automatic.
His response is quite similar, almost exactly the same.
That got me to wondering about what others are seeing.
Steven then asked a great question about tire size ..... that will affect the results.
I'm running 195 R 14s
Steven is running 215 R14's
Then I was googling any reference information and I ended up on Kam,s old blue site.
I found a chart about rpm and speed.
I found it unsettling that the rpms on her chart are significantly less than we are seeing
Forgive me Kam but I shamelessly stole your chart.
You have the powers to edit it away or properly insert it with proper credit given......
your site is the only place that I've seen it.........
I will need to take a ride and check my 50 mph rpm's.
Anyway, please post your cruising speeds, rpm at each speed and tire size.
50
55
60
65
70 or faster if you are so inclined....... I'm not.
If you know Transmission code that you have, that would be awesome!
Thanks!
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Ghia
http://www.thesamba.com/vw/forum/viewtopic.php?t=392473
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http://www.thesamba.com/vw/forum/viewtopic.php?p=6315537#6315537
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https://www.thesamba.com/vw/forum/viewtopic.php?t=482968&highlight=74+super+vert
Last edited by djkeev on Sat Mar 23, 2024 1:33 pm; edited 1 time in total |
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skills@eurocarsplus
Samba Peckerhead
Joined: January 01, 2007
Posts: 16893
Location: sticksville, ct.
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| Posted: Sat Mar 23, 2024 10:32 am Post subject: Re: Automatic RPM vs MPH |
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i'm about 4200 at 75 but I have a tall tire in the rear 225/60/17
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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....... |
| Jake Raby wrote: |
| Thanks for the correction. I used to be a nice guy, then I ruined it by exposing myself to the public. |
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jimf909 
Samba Member
Joined: April 03, 2014
Posts: 7483
Location: WA/ID
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| Posted: Sat Mar 23, 2024 11:46 am Post subject: Re: Automatic RPM vs MPH |
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Won't you also need to know the diff ratio? There are at least three, er, four ratios available.
https://countryhomescampers.com/product-category/replacement-parts/transmissions/
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- Jim
| Abscate wrote: |
Do not get killed, do not kill others.
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Current: 1990 Westy Camper - Bostig RG4, 2wd, manual trans w/Peloquin, NAHT high-top, 280 ah LFP battery, 160 watts solar, Flash Silver, seam rust, bondo, etc., etc.
Past: 1985 Westy Camper - 1.9 wbx, 2wd, manual trans, Merian Brown, (sold after 17 years to Northwesty who converted it to a Syncro). |
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MarkWard
Samba Member
Joined: February 09, 2005
Posts: 17159
Location: Retired South Florida
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| Posted: Sat Mar 23, 2024 11:53 am Post subject: Re: Automatic RPM vs MPH |
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Assuming stock ring and pinion and tire, I’d expect to be able to get near redline in drive on the flat, no headwind probably around 80 mph. Don’t have the specific detail you are looking for.
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skills@eurocarsplus
Samba Peckerhead
Joined: January 01, 2007
Posts: 16893
Location: sticksville, ct.
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| Posted: Sat Mar 23, 2024 12:50 pm Post subject: Re: Automatic RPM vs MPH |
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correct. I have a stock setup and ran the taller tire as the trans builder had issues with the aftermarket R+P
_________________
| gprudenciop wrote: |
my reason for switching to subaru is my german car was turning chinese so i said fuck it and went japanese....... |
| 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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Red Ryder
Samba Member
Joined: June 26, 2021
Posts: 958
Location: Northern California
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| Posted: Sat Mar 23, 2024 2:38 pm Post subject: Re: Automatic Transmission, RPM vs MPH |
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Dave,
Our rpm vs mph readings are very similar with 205/70r14 tires on stock alloys. Sounds fine to me.
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“Scarlett” — 1990 Vanagon Carat Wolfsburg Edition
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djkeev
Samba Moderator
Joined: September 30, 2007
Posts: 32648
Location: Reading Pennsylvania
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zerotofifty
Samba Member
Joined: December 27, 2003
Posts: 1579
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| Posted: Sat Mar 23, 2024 3:24 pm Post subject: Re: Automatic Transmission, RPM vs MPH |
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your old tranny may have had dirt in it causing it to slip less???? Also maybe the clutches in the new one need to bed in, thus they is slipping more now, I dont know nothing about the van automatic tranny however, I only have dealt with an automatic in a Jeep, an AW4 type. My Van is a stick shift tranny.
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kamzcab86
Samba Moderator
Joined: July 26, 2008
Posts: 7931
Location: Arizona
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| Posted: Sat Mar 23, 2024 3:49 pm Post subject: Re: Automatic Transmission, RPM vs MPH |
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| djkeev wrote: |
| I found it unsettling that the rpms on her chart are significantly less than we are seeing |
A) I used the calculator that was listed as a source in that document. Online calculators automatically use a standard 0.7 ratio for an auto trans, which I didn't know until now.
B) I used 25.6" for tire diameter, which is slightly off from the 25.3" it should be.
C) Online calculators do not factor in the torque converter. According to Roadkill Garage, a torque converter can add anywhere from 3 to 12%, depending on condition.
D) I've now redone those tables using Excel for a more accurate calculation, based on each transmission's stock final drive, the revised stock tire diameter and adding 3% for torque converter (manual trans section also updated).
Those figures should be more in line with the VW transmissions in stock form. Those figures, obviously, do NOT take into account road conditions, tire condition, tire tread, weather condition, vehicle weight, and so on. The tables are based on mathematical calculations of when the vans were new, NOT an average of what drivers are seeing 30+ years later, after hundreds of thousands of miles, after untold rebuilds, after modifications, after installing larger tires, with worn out gauges (or reassembled), etc. In other words, math is being used to get set parameters, instead of using multiple variables resulting in multiple parameters.
To answer your question, my 1990 Westfalia with rebuilt (in 2008) transmission and 205/65-15 Cooper Discoverer tires, which have a diameter of roughly 25.5":
68-70 mph = 3850-4000 rpm
^That's using GPS for speed & the tach has never been taken apart. Note that RPM is basically in line with the revised table. Who knows what it was reading back in 2008 after its rebuild (didn't buy the van until 2010).
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1986 Cabriolet: www.Cabby-Info.com
 1990 Vanagon Westfalia: Old Blue's Blog
2016 Golf GTI S
"Real knowledge is to know the extent of one's ignorance." - 孔子 |
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djkeev
Samba Moderator
Joined: September 30, 2007
Posts: 32648
Location: Reading Pennsylvania
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kamzcab86
Samba Moderator
Joined: July 26, 2008
Posts: 7931
Location: Arizona
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| Posted: Sun Mar 24, 2024 12:21 am Post subject: Re: Automatic Transmission, RPM vs MPH |
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| djkeev wrote: |
| I'm beginning to see that if you want to travel @ 65-70 mph..... you are going to be spinning close to or a tad over 4000 rpm's with an automatic transmission. |
That's the name of the VW game until more modern times... including the manual transmissions. A common question in the Cabriolet world, particularly new owners who have never owned an old VW: "On the highway, is xxxx RPM at xx MPH correct, or is my trans about to blow up?" Yep, normal.
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~Kamz
1986 Cabriolet: www.Cabby-Info.com
1990 Vanagon Westfalia: Old Blue's Blog
2016 Golf GTI S
"Real knowledge is to know the extent of one's ignorance." - 孔子 |
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AceTaylor
Samba Member
Joined: July 15, 2009
Posts: 139
Location: PERKASIE, PA
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| Posted: Sun Mar 24, 2024 5:10 am Post subject: Re: Automatic Transmission, RPM vs MPH |
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| I don't know if it is coincidence, or there's a mechanical reason for it, but my 4 cyliner bus runs about 4000 rpm +/- at 70 mph. My 6 cylinder car runs about 3000 rpm +/- at 70 mph and my 8 cylinder car runs about 2000 rpm +/- at 70 mph. Do the math and it works out to be about the same piston pulses (power strokes) |
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AndyBees
Samba Member
Joined: January 31, 2008
Posts: 2336
Location: Southeast Kentucky
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| Posted: Sun Mar 24, 2024 8:49 am Post subject: Re: Automatic Transmission, RPM vs MPH |
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Subscribed for good reading...
Not an automatic, but my 215/75/15 tires drop the RPMs by about 150 vs the OE size tires.
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1983 Air-cool, 225k miles, 180k miles mine. Seven trips to Alaska from 1986 thru 2003. |
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Wildthings
Samba Member
Joined: March 13, 2005
Posts: 50360
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| Posted: Sun Mar 24, 2024 9:01 am Post subject: Re: Automatic Transmission, RPM vs MPH |
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| In stock form for a US model you should see about 4000 rpm at 70 mph. The longer gearing was for the higher compression motors sold in Europe and elsewhere. FWIW, with a 2.2 Subaru, I find the factory gearing works well up to around 6000' elevation, while above that it gets wimpy. |
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djkeev
Samba Moderator
Joined: September 30, 2007
Posts: 32648
Location: Reading Pennsylvania
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Shonandb
Samba Member
Joined: January 12, 2019
Posts: 1204
Location: Vancouver, BC
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| Posted: Mon Mar 25, 2024 4:29 pm Post subject: Re: Automatic Transmission, RPM vs MPH |
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I have the 010 Vanagon Auto in my Bus with 225/75/16 LT Tires and was out on the Hwy yesterday and was running:
~3400 rpms at 60mph
~4000 rpms at 75mph
My rpms are about 500 rpms lower now than with the stock 185R14 Load D tires which was approximately 3900rpms at 60mph and 4500rpms at 75mph
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76 Westy with a 2.5L Subaru SOHC + Vanagon (010) Automatic Transaxle
Build & Trip Thread: https://www.thesamba.com/vw/forum/viewtopic.php?t=758760
Previous 1973 Panel Bus:
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