OK here is my dilemma. I think my rear is starting to go bad.

Noticeable clunk when going on and off gas.

when I go under it and watch the shaft I am getting between 45 and 90 degree of shaft rotation between drive and reverse.

My question is if I go with a 2.47 from a gasser will I need to modify tranny for a 1st gear start?

Also how long of a project is it to swap the rears?

TIA

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86 300SDL. 250,xxx on #14 Head. One eye always on temp gauge.. Cruising towards 300K

What's the rear got to do with the tranny first gear start? Pretty sure nothing.

A clunk alone would'nt suggest a bad diff to me. Accompanied by whining would. Make sure the flex disks and diff mount are good.

Don't all SDLs have first gear start?

I would think you could do it in a couple of hours. Maybe half a day working slowly.

Sixto
87 300D

I think he means taking off in second coupled with the long legs of a 2.47 rear will result painfully slow acceleration.

Sixto
87 300D

You are correct. I have a 30 mile highway run back and forth to work every day. the part I worry about is the in town portion at both ends.

I know it will help some on the fuel mileage.....but I already average about23-25mpg.

Will look deeper into the rear today ans this week. Just go off a 13 day stretch of 12 hour night shifts

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86 300SDL. 250,xxx on #14 Head. One eye always on temp gauge.. Cruising towards 300K

Where I live at you are either going up hill or down hill.. the 1st gear start is for getting off the line(especially with a 2.47)

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86 300SDL. 250,xxx on #14 Head. One eye always on temp gauge.. Cruising towards 300K

Make sure you have enough revs at your anticipated cruising speed with the 2.47 to keep the torque converter fully engaged. If you drop much below 2000 rpm, you might be in the stall range of the torque converter and the slip will hurt mpg. It'll be a double whammy in hilly country if you have to downshift and wait for boost to build frequently.

Sixto
87 300D

By my calculations with a 2.88 now(I think that is the stock if not someone please correct me) going to a 2.47 would drop me from 3100 at 75 down to 2650. I just need t get the time to do it. Along with getting the cash together with out the wife noticing

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86 300SDL. 250,xxx on #14 Head. One eye always on temp gauge.. Cruising towards 300K

I don't advise making this swap unless you currently have more than sufficient power for your particular style of driving.

This engine doesn't produce much power below 2800 rpm and it really prefers operating between 3000 and 3500 rpm.

At 2650, you're going to wait for it to do any acceleration. Climbing any decent hill at 75 mph will be impossible without a 4-3 downshift.

Furthermore, if you frequently encounter traffic that drops your speed to 60-65 mph, the engine has nothing at 2200 rpm in fourth.

OK thanks for the input. The reason I was looking at the ratio change is I found a good one(2.47) at a reasonable price from a member here. I guess I will have to find a stock one.

Thanks again

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86 300SDL. 250,xxx on #14 Head. One eye always on temp gauge.. Cruising towards 300K

How have you concluded that you need a new diff?

Sixto
87 300D

Without pulling the cover, (next week end) I have arrived at that from the loud clunk on and off the gas and the excessive back lash(I might be call it the wrong thing) I can move the drive shaft almost 90 degrees before the wheels move. I looked at the flex disc and axles today nothing broken nothing loose.

I am figuring the diff is the culprit. If I missed something let me know.

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86 300SDL. 250,xxx on #14 Head. One eye always on temp gauge.. Cruising towards 300K