The odometer on my recently purchased 1985 300TD-t only shows about 80% of the actual mileage.

I know that it is *not* the original speedo.

it currently has a 150MPH speed o that shows ~ 58mph at 3000rpm
( if my calculations are correct, when i show 58, I'm doing 72..unless I'm cracked)
a 'spare' 100mph speedo, along with the 85 mph one from my 1982 240D both show ~ 54mph at the same RPM.

I've found the parts numbers for proper replacement speedo's
(per EPC online seems 85mph and 125mph versions are available)

*o.k. to the point!*

teh parts numbers i have are:
a 009 542 67 06 ( 85 mph)
a 010 542 75 06 (125mph)
a 011 542 68 06 (125 mph)
(along with some others that "are replaced by" newer part numbers such as those above)

the parts numbers that i *SEE* on the speedos are written as:
123.542.37.01 (in the case of the currently installed one)

how do i cross-reference these? (is it as simple as ignoring the leading set?)

I'd hate to spend money on another unit designed for a different rear-end-ratio.

thanks!!

Robert

I don`t know about your part #. the spedo on my 85 300D has a part#
of 123 542 27 57. my understanding is all 85`s have the 2:88 differential.

60mph Iam@ 3000rpm
65mph 3200 - 3300rpm
55mph 2500 - 2700rpm

the spedo is matched to the diff gear ratio.

hope this helps

charlie

__________________
there were three HP ratings on the OM616...

1) Not much power
2) Even less power
3) Not nearly enough power!! 240D w/auto

Anyone that thinks a 240D is slow drives too fast.

80 240D Naturally Exasperated, 4-Spd 388k DD 150mph spedo 3:58 Diff

We are advised to NOT judge ALL Muslims by the actions of a few lunatics, but we are encouraged to judge ALL gun owners by the actions of a few lunatics. Funny how that works

I second that is the correct speedo part # for your '85.

__________________
1983 123.133 California
- GreaseCar Veg System

hmm those RPM values got me thinking

*I* show
60mph @ ~ 3100
67mph @ ~ 3500

(on 195/70R14 tires)

those seem to be about in-line then.

leaving me to wonder about my odometer. I took a number of readings vs. mile markers on an interstate over 400 miles round trip.

the ODO seemed to be consistently 80% off
as opposed to working 80% of the time, then stopping altogether for a bit etc
(this is the part there i *assumed* that the whole works was)

maybe another roadtrip is in order.

scary math time
(aka me thinking out loud)

when my speedometer reads 60mph I'mshowing 3100rpm on the tach

3100 RPM * 60 = 186,000RP-hour (engine)
if final transmission ratio is 1:1
186,000RP-hour (driveshaft) / 2.88 =
64583.3 RP-hour rear axle

195/70R14 tires get either 852 or 836 revs per mile dep. on brand

64583/852 = 75.8 miles in that same hour

for better or worse the above seems to work out to what i *thought* was happening..when taking real- world measurements.
(my odo would show 60 miles...80% of the 75miles the interstate said i'd traveled

i am assuming the tach is right


brain = ow

robert