85 to 120 mph Speedo Conversion - PeachParts Mercedes-Benz Forum

MBDFahrer · #1 03-17-2007, 10:06 PM

Tried the search, and it returned no results?

What needs to be done to convert a 82 SD from a 85 mph speedo to a 120 mph one?

#2 03-17-2007, 10:11 PM

Replace the speedo with a 120mph unit.

Just be sure the speedo you get is from a car with the same rear end ratio.

300SD81 · #3 03-17-2007, 10:28 PM

I want to do this too. Just pretty low priority on my list of things to upgrade/fix.. My speedo dosen't even work anymore... But I guess its a good excuse if I get a ticket, I used to peg it all the time, and now...probably even more... Is there a list of cars and what rear end they have?

#4 03-17-2007, 10:34 PM

Quote:

Originally Posted by 300SD81

I guess its a good excuse if I get a ticket,

Not only would you get a ticket for speeding, you would also get a ticket for defective vehicle!

If you do get a speeding ticket, DO NOT tell them your speedo does not work. DO NOT even tell the how fast you *think* you were going.

derherr65 · #5 03-18-2007, 12:49 AM

Why? Will your SD really pass 85mph? Engine wise I mean.

#6 03-18-2007, 01:28 AM

Quote:

Originally Posted by derherr65

Why? Will your SD really pass 85mph? Engine wise I mean.

A stock 240D can pass 85mph on it's own power, eventually.

MBDFahrer · #7 03-18-2007, 02:26 AM

She has no trouble getting up to 85. Pretty sure she doesn't stop accelerating there

*edit*

I'm also tired of hearing "kids" heckle me for having a car that can't do triple digit speeds (doesn't have to, just show it could).

[Bratty voice] "Your car is slower than a Acura TL/G35"

Maybe I should just get some new friends

H-townbenzoboy · #8 03-18-2007, 02:30 AM

Isn't the factory listed top speed for the 81-84 300SDs something like 103 or 105 mph?

PatricdeBoer · #9 03-18-2007, 04:39 AM

Heck, I've taken my 300sd to at least 100. It does it no sweat.

derherr65 · #10 03-18-2007, 09:51 AM

Huh. Mine sure does struggle past 80 or so. Thought I just found out my wastegate is busted, and probably has been the whole time I've had it. So that may be more of a fuel cut out issue for me.

winmutt · #11 03-18-2007, 10:29 AM

Quote:

Originally Posted by ForcedInduction

Not only would you get a ticket for speeding, you would also get a ticket for defective vehicle!

If you do get a speeding ticket, DO NOT tell them your speedo does not work. DO NOT even tell the how fast you *think* you were going.

That really depends on the state you are in.

pmckechnie · #12 03-18-2007, 12:44 PM

Get a speedometer from something like a 500SEL, 560SEL, etc which goes to 160 MPH and your friends will thing your car will outrun anything they have ever seen.

pawoSD · #13 03-18-2007, 04:41 PM

My dad's SD has the 160mph speedo in it.

Fastest we've ever gotten that car up to is "121mph" however, it reads exactly 7mph fast due to the incorrect diff ratio. It is expecting a 2.47 but the SD has a 3.07.

Strangely enough, his odometer reads 100% accurate.

This was confirmed by driving behind him while on the phone, it said a mile at the same time as mine....also, it matches the freeway mile markers. Odd.

I'll admit the 160mph gauge does look cool, but its also depressing since we can't go that fast....and its harder to see the small increments. I like the big gaps of space between each 5mph on the 85 speedo (which my car has).

Personally I have pegged the 85mph speedo almost to the bottom of the housing, thats where it stopped....I was still accelerating....and the odometer stays accurate when going above what the needle registers.

derherr65 · #14 03-18-2007, 06:08 PM

Quote:

Originally Posted by pawoSD

Fastest we've ever gotten that car up to is "121mph" however, it reads exactly 7mph fast due to the incorrect diff ratio.

It reads 7mph fast at what speed? Remember it's a percentage, not an absolute number of miles per hour. My speedo reads 5% slow. That's 3mph at 60, 3.5 at 70, and so on.

I agree, I like the 85mph speedo because of the large gaps between speeds. I can actually see the difference between 60 and 65. Try that on you 160mph speedo.

300SD81 · #15 03-18-2007, 06:24 PM

I found out that it was my speedo that was busted, not the wiring in the car. How hard is it to convert a 160mph speedo from a gasser to be accurate in a 300SD? I should have written down what car I pulled it from... But it reads 100-110mph when I'm going somewhere between 70-80mph, any gusses? My old speedo works occasionally for a few seconds, so I'm guessing its just a loose connection somewhere, probably fixable, if so, anyone interested in buying the one I pulled?

My SD easily passes the 85mph on the old speedo, I've had it up to around 120mph once (gps)