85 300sd transmission swap...more problems - PeachParts Mercedes-Benz Forum

farmmedicoh · #1 05-17-2011, 07:00 PM

i just finished installing a used transmission into my 85 300sd
i overlooked the fact that i had failed to refill the transmission once i was done
once it was on the ground i drove it around my circular drive to pull it in front of my garage
it had zero power
i mean nothing
i chalk this up to the lack of fluid
in my haste to get this job done i had forgotten to pick up more fluid and only had about 1.5 quarts available at the house
so i had to drive it to the auto place to get some
now
i noticed that the more fluid i put into it the easier it shifted
what i notice now is that it feels sluggish
was a fairly zippy car before
well
as zippy as an old diesel could ever be
as i was approaching home i thought i would wind out the engine to see what it would do
i couldn't get over 50 mph
my question
did i burn my new/used transmission?

pawoSD · #2 05-17-2011, 07:10 PM

How much fluid was in it when you drove it around after installing? By no power do you mean "engine rev'd but it didn't move"? Does it currently shift to all 4 gears properly? You might have not connected things like the bowden cable and vacuum adjustment properly or it is way out of adjustment.

farmmedicoh · #3 05-17-2011, 07:24 PM

How much fluid was in it when you drove it around after installing? By no power do you mean "engine rev'd but it didn't move"? Does it currently shift to all 4 gears properly? You might have not connected things like the bowden cable and vacuum adjustment properly or it is way out of adjustment.

i would say there was maybe a half quart?
i don't really know
yes the engine reved fine and car barely moved (at first)
now it just feels sluggish and won't go very fast
i have no idea what the bowden cable is or how to adjust the transmissions vacuum system
any hints?
i feel like i hooked everything up

tyl604 · #4 05-17-2011, 07:27 PM

Check to see if you knocked off the line to the switchover valve. I just put a used tranny in my 81 300SD and experienced exactly that power problem; hard to get it over 35mph. It was just that the line going from the switchover valve on the inside fender had come off at the other end - where it attaches to the back of the engine, passenger side, on a nipple. Slipped it back on and presto pep was back.

I have really learned a lot about adjusting the vac for a new tranny. You might want to look at the posts on my thread called something like "81 SD used tranny goes clunk." I have it adjusted just about right now and am quite happy. Really pretty easy after you learn how to adjust the vac modulator, adjust the WOT gap on the proportioning valve, and adjust the proportioning valve itself.

If you had 1.5 quarts in it, the tranny is probably OK. That's quite low but in my experience not enough to damage it. I used to drive mine low until it started not wanting to shift, then I would go back home and add some fluid. Did that for some 6-10 years because I did not want to spend the money to replace the seals. These transmissions are really tough.

farmmedicoh · #5 08-21-2011, 10:59 AM

sorry for not getting back to this for so long
i had to stop working on the 85 right then b/c of needing to leave town
pulled all the parts back off the 85 (front calipers, all 4 shocks, all 4 tires and the rear seats) and put them into the 82 (parts car) for the trip
finally back home and parts car has sent me several very clear messages that it is finished with driving around and that i need to get the other car going
so i put all those parts back into the 85
drained off most of the very old diesel that was in it for 1.5 years and replaced it with fresh stuff and some fuel system treatment
seemed to help out a tiny bit
but the shifting was still a bit wonky
sometimes it goes 2-3 super fast
sometimes it struggles to go into 1
sometimes it won't shift unless i let my foot off the gas pedal and then it slams into the next gear
after taking it for it's first "long" drive (about 30 miles), it only got the first 20 before it simply refused to go into gear at a stop light
(i, unfortunately, was not in the car at the time)
after cooling for an hour, it started right up and finished the journey
later today we get to play the "how far will it go" game again
but something clearly is wrong
very clearly
apparently it got very smelly when it refused to shift
and there is an intermittent "whirring" that is in time with the shifting and located just forward of the tranny
an unhappy sound if ever there was one

i've been working my way through the vacuum adjusting info you suggested and it reads a bit like swahili to me
you obviously know your landmarks way better than i do (which isn't saying much at all b/c i'm guessing my way through all of this)
some of the side reading i am doing has suggested that the 85 added parts into the vacuum system that weren't there earlier
any chance that these are the issue?
or at least they are what is causing the need for adjustment?
i have no idea what year the replacement tranny is

tyl604 · #6 08-21-2011, 05:07 PM

It's pretty simple to find out if the shifting problem is vacuum or the tranny. Buy a Mityvac and hook it to the vac line coming from the vac modulator on the transmission. Unhook the line from the vav temporarily. Drive around with no vac to the transmission. If it upshifts OK, you have a vac problem. If it downshifts with a clunk, that is normal; just pump up the Mityvac after you upshift all the way - when you come to a stop with the vac pumped up, it should downshift smoothely. If it still clunks, it is not a vac problem.

If it is not a vac problem, then it is most likely a transmission problem. Or a Bowden cable adjustment problem but probably tranny. Do not worry about adjusting the vav or the gap until you figure out if the tranny upshifts properly without vac.

kerry · #7 08-21-2011, 05:49 PM

Some transmission mated to the 617 are quite different from other transmissions mated to the 617. So first, I'd try to figure out what transmission I had and how compatible it is with an 85 SD. The transmission part number will begin 722.XXXXXXXX. I'm not very familiar with the numbers but a little searching should reveal a lot.

tyl604 · #8 08-21-2011, 07:50 PM

Yes, I bow to Kerry's expertise.

farmmedicoh · #9 08-22-2011, 08:21 AM

ordered a mityvac last night
will advise soon as i know something
thanks for the help

farmmedicoh · #10 08-22-2011, 06:19 PM

here is a thought
over the last winter (while i was waiting for the snow to melt so i could finish the tranny install) i "fixed" the ignition switch problem i had
problem was that turning the key won't engage the starter
after i hooked everything back up this May, i noticed that the oil pressure gauge shows no pressure what so ever
maybe it's a loose wire (which i doubt)
could this lack of pressure be somehow affecting the tranny?
i didn't touch the engine while putting the tranny in
well
not a bunch
any thoughts?

kerry · #11 08-22-2011, 06:51 PM

126 SD has an electrical oil pressure gauge. Your no-start and no guage problems are probably related. Check the wire connection at the back of the ignition switch.

Probably no relation to the transmission problems.

oldsinner111 · #12 08-22-2011, 07:05 PM

I'd say here roasted his clutch packs trying to drive on low fluid.Filter is now clogged.

farmmedicoh · #13 08-25-2011, 08:38 PM

got the Mityvac
did the tranny to vac ting at 15 psi
smooth going up
didn't notice any issue going down either
been brushing up on my swahili but still having trouble finding pertinent info
dark out now
so gotta stop
no shop to pull it onto

farmmedicoh · #14 08-26-2011, 10:55 AM

with the new(old) tranny installed, could it's lack of being set to this car cause it to make noise?
the high pitched scream seems directly associated with the tranny speed and also seems to come from the general area of the forward end of the tranny where it hooks to the engine

farmmedicoh · #15 08-26-2011, 01:28 PM

went thru the vac system as best as i could with the limited knowledge i have
found what seemed to me to be a couple of loose fittings
haven't adjusted anything yet
figured i would go a step at a time before i do anything drastic
leaks tightened up
seems to shift better
still hangs a bit (waits till 4000rpm) in 2-3 on WOT but otherwise shifts pretty well
half throttle it seems fairly good
though it did jump 2-3 in less and a second going down hill once
havn't tried to drive with vac guage in the line to tranny yet
taking it for a longer drive shortly (20 miles 1 way)
the whine/rattle still bothers me
will advise