Speedometer accuracy

[pdunn13445]

Have an '84 Westy Wolfsburg GL with the tachometer option and auto trans. In a reply to how tach was wired in I again confirmed that the speedometer is not all that accurate. I figure roughly 10 mph high at higher speeds. For instance at 4000 rpm reads 87 mph, but actually about 75 mph? Does anyone have a reference to engine rpm w/ auto tranny in top gear and actual mph? It would be nice to know what my speed is, even within 5 mph.

[Wildthings]

What size tires are you running? The speedometer works off the left front wheel, it is in no way affected by the kind of transmission you have or your gearing, just tire size.

[0to60in6min]

Given stock 14" rim.... 4000 rpm is 70 mph... give and take a few miles error due to wear and tear of the speedometer..

[tikibus]

The Speedo of the 84 is funky.

Tiki and I get to do math while driving. Running on stock rims and 14" tires gives a reading of 10 MPH higher on the Speedo. When doing 40, doing 30, etc..

Never Have I gone to muck about with the cables.

What I have done is to find a area ( construction or school) with a reader. Blinks or numericaly shows your speed and gauge off of that.

Hence my destain with NYS Thruway (90). I can only go so fast, Some get it, some don't. Much rather do the old school roads.

Puttin' along with a smile. Enjoy the ride.

_________________
Happy Trails!
Mark
______________
Founding member of the Empire State VW Camping Club.
http://www.empirevwcamping.org/
1984 Westy - Tiki
1997 Honda Civic -The Green Hornet
1971 Volvo P-1800E- needs TLC

[msinabottle]

Winston's '84 speedometer has also been funky--and it's the second one I've had in him, don't worry, CrimeStoppers, I left a note in the owner's manual. The huge Big O knobbies he'd had on him before undoubtedly screwed up the reading a bit, but he's been a LOT better since I put DogPilot's old 15" Audi rims on him and the Michelin Agilis.

Supposedly, those are just the same size as the stock rims. If you have one of those radar speed limit signs on a road you drive, check often and learn. Winston's quite on at low speeds. For faster speed, you could zoom... All right, amble... Past a State Patrolman and see if he gives chase, but more easily, get a GPS of any description and use it to compare its hyper-accurate speed reading with your speedometer.

Long the '84's! Yay for the Round-Eyes!



Best!
_________________
'Winston,' '84 1.9 WBX Westy
Vanagon Poet Laureate: "I have suffered in
many ways, but never, never, never in silence."

[Perales]

Could be that VW was just trying to make us feel better.
Or was it the law just trying to be clever.
Here it is from the Bentley

It's a conspiracy man!
_________________
-- 1987 Westfalia automatic (Captain Vino)

[pdunn13445]

First of all, I blew it by not relating rims and tires, which in this case are both stock. Second, the question involved the tach reading and speeds at specific rpm's, therefore the tranny, thus gearing does make a difference. So with all your input, it is still anybody's guess as to actual speed. I do like 70 mph at 4000 rpm, but I swear it feels faster in Shirley. Also love the clip about the speedo head. At 60 mph I think the difference was about 10 mph, or actually doing 50, so the clip is close. But my, like I said 4000 rpm indicates 87 mph. I will have to do my math and get a curve going. Here in Mexico my general rule is that the Federales on the toll roads will maybe stop you if you are on radar going over 100 mph.

[tencentlife]

I don't think you would be going 70 at 4k with an automatic unless your tires were fairly oversized. I have near-stock OD tires and a tall 4th in my standard, and that's nearly my speed at 4k. As I recall the automatic's final gearing is pretty low, but I don't have my book. There's an online listing of all the trannys in German (Getriebe), but I can't find the link either. Perhaps someone could chime in with the ratios, it's not hard to figure out your mph/rpm from there.

Anyway, all DOT-approved speedos have to read correct or high, as has ben pointed out, and the early Vanagon speedos typically read really high. The same applies to those roadside radar guns; they add the same 3mph a cop has to subtract from his radar gun, to give the 3mph error in your favor. Having a GPS is probably the best and easiest way to confirm your actual speed.

If you don't mind a lot of trial and error tweaking, it's not hard to recalibrate your speedo to read correctly with whatever trans/tire combo you're on. You end up doing it several times unitl you get it dialed in. I got so good at it, I could have the head out, tweak the spring, and reinstall in 11 minutes!
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Please don't PM here, I will not reply.

Experience is kryptonite to doctrine.

[Christopher Schimke]

[UH60Driver]

Just use a GPS to verify where you are at speedwise. If you dont have one or cant afford one(because you spent all you money on your van), certainly you know someone who has one that can go on a van ride with you to take a few readings at different speeds.

[j.a.c.auto]

This what you are looking for?
http://brickwerks.hostinguk.com/VehicleSpecific/T3/info/gbx.htm

[jackbombay]

[tencentlife]

http://brickwerks.hostinguk.com/VehicleSpecific/T3/info/gbx.htm

Yeah, that's it. I also found a pdf I saved which is the German version of that same data.

If an '84 auto has the 4.09 FD x the 1.0 3rd gear, the effective ratio is 4.09. Most late wbx 4 speeds are 4.83FD x .85 4th for 4.10. So the auto is actually top-geared pretty much the same as a standard, all else being equal. I do remember in the book that with stock-sized tires, you get 18mph/1000rpm, or 72mph at 4k. If you're reading 70 at 4k, then your speedo is pretty much on target. For stock tires, that is.
_________________
Shop for unique Vanagon accessories at the Vanistan shop:
https://intrepidoverland.com/vanistan/

Please don't PM here, I will not reply.

Experience is kryptonite to doctrine.

[Perales]

Here is another chart for the collection
http://www.vanagonparts.com/tranny_id.html
_________________
-- 1987 Westfalia automatic (Captain Vino)