3.07 to 2.88 speedo change? - PeachParts Mercedes-Benz Forum

DieselBone · #1 01-22-2007, 03:15 PM

My weekend job is going to be swaping rears in my TD and replacing the axle shafts. From my searching I found that it really isn't worth it to change the speedo around to calibrate for the 2.88 gears. Is this true?
Thanks

Ken300D · #2 01-22-2007, 03:41 PM

Not worth it at all. You'll probably have a more accurate instrument reading than you did, once you change out the differential. Seems the odometers are always calibrated to read higher than you are actually going - to slow you down a bit. Once you change out the differential, it will be closer to the actual speed you're going if your experience is like mine.

Your mileage (pun intended) may differ.

Ken300D

R Leo · #3 01-22-2007, 04:05 PM

When I swapped out the 3.07 with a 2.88 in the 300D, the speedo error was about 5 mph. I found a speedo out of a car with a 2.88 and installed it in the cluster. Easy fix.

#4 01-22-2007, 07:13 PM

Your old speedo should read about 6-7% too low with the new gears. You have to decide if that's OK or not. If you can find a speedo from a 85 300D or 300TD, it should work correctly with the 2.88 gears.

DieselBone · #5 01-22-2007, 08:44 PM

Hey guys thanks for all the good information. Since I have the whole `85 300TD I think I might go ahead and change the speedo. I wasn't sure if it was the speedo, or if it was the gear(s) in the tailshaft that needed changing, kinda like its American counterparts. Thanks again guys, I can't wait to see if it makes a difference.

rwthomas1 · #6 01-22-2007, 10:49 PM

Let me know how it goes. I have a 2.88 diff and cluster to go into my '84 for almost 2 years now..... Finally getting to it. RT

DieselBone · #7 01-22-2007, 11:15 PM

Quote:

Originally Posted by rwthomas1

Let me know how it goes. I have a 2.88 diff and cluster to go into my '84 for almost 2 years now..... Finally getting to it. RT

Will do, should be done by Sunday.....I hope

DieselBone · #8 02-09-2007, 11:31 PM

UPDATE!!!!!

Well, does anything go as planned.....NO!!!!

I still haven't got the job done yet. Just minor set backs, like my Father getting the wrong axle shafts (not his fault) Somehow we got the shafts with the flanged end, but we needed the splined on both ends. However the new ones are flanged, but with the output shaft already bolted on the axle. BTW, does anyone know the deal with the axle types, our 85 still had the older type too, I thought the cut off was 80-81? Tomorrow I'm gonna try again, I'll take some pics. Wish me luck.....

t walgamuth · #9 02-10-2007, 06:48 AM

i have always found benz speedos to be pretty accurate if the correct sized tires are mounted.

i have had 29 benzes.

tom w

engatwork · #10 02-10-2007, 10:18 AM

I put a 2.07 rear in my normally aspirated '81 300d and the speedo looks to be 8-10 mph slow. The increase in fuel mileage is GREAT though

. Based on what I can tell it is more than 30 mpg now

.

barry123400 · #11 02-10-2007, 01:47 PM

Just love that typographical error.

At least you help displace the ideal it does not increase milage. Seem much slower on initial acceleration? I suspect the transmission could compensate for that a little.
My 77 300d is fairly strong for what it is but should be revving a little slower on the highway or should I say I just would preffer it to.
This kind of satifaction with a change makes others like myself want do it. Even worse is my 240ds scream for some change like the five speed. There was one for sale yesterday. I wanted to bite but it did not have the shifter and linkage. That may be as hard to come across as the transmission. Not as common in europe as I had hoped either. They apparently sold the four speeds over there as well I was told. Just gotta have some five speeds and alternate rear ends. The hard part is explaning to the wife exactly why I am replacing what is already good in her eyes. That proccedure deserves a thread of it's own.

The actual installation is nothing in comparison.

Brian Carlton · #12 02-10-2007, 05:35 PM

The SD has the 2.88 gears installed. The change, coupled with +2 tires, yields a 10% reduction in engine speed. It's turning about 2900 at 68 mph. Perfect speed.......just before the 617 "growl" kicks in.

The SD can get 30-31 mpg on summer fuel without a/c.

It's currently in the 27's with the winter fuel.

For those with the electronic speedo (SD's), there is an electronic recalibrator available that will adjust the readout so that it's perfect (within .5%). The cost of the unit is $80. but, I'm pleased with it.