OK,

So I got a used 722.303 tranny and installed it into my 83 300sd.

good news: its working

bad news : its slipping *BUT* When I disconnect the vacuum line to the modulator it slips MUCH LESS

Is that an adjustment thing or do I need another modulator? From what I have read that when a modulator goes bad it bangs into gear. the opposite of my situation.

Also , I have read on this forum that using type F fluid will make the transmission slip less and have firmer / harder shifts. Should I use type F? I like hard shifts.


I was thinking of using synthetic , probably mobil 1 or royal purple or redline, but if I Should use type F, then What do I do?? Is there a synthetic type F fluid??

Get yourself a mightyvac to check the vac at the vacuum control valve and check to see if the modulator holds vacuum. Search this forum, there is a wealth of info to help you fine tune your trans.

__________________
'83 240D 264k on 100% biodiesel/ 31mpg
83 300D 217K the $800 gem
'82 300D 267K the new WVO project car finished and driving for free
International tractor B275 on B100
Ford 555 backhoe on B100
Sargent 25 ton Rough Terrain crane on B50

The fact that it slips without any vacuum to the modulator is not a good sign. But, you may be able to obtain some better performance by increasing the modulator pressure. There is a folding T handle under the rubber cap. Open the T handle and turn it clockwise by three turns.

Take the vehicle for a drive and see if the flaring is eliminated.

When the modulator gets no vacuum, it normally shifts too fast and bangs. It's quite normal for this to occur with a properly functioning modulator.

Would this be the same situation if the modulator is bad and does not hold the vacuum?

Do modulators go out of adjustment?

and what about Fluid? "synthetic type f" ??

Your problem is flaring. The modulator can't cause flaring, AFAIK, without any vacuum supply. The default position (non-functional) is no vacuum and hard shifts.

If you don't get hard shifts.........I don't believe that a replacement modulator will solve your issue.........but, I'd like further comments from folks that know the internal workings of these beasts.

Fluid is Dexron III........not type F.

OK, then what causes Flaring?

I can't give you the detailed technical explanation (because I don't know the box well enough), but, flaring is common on older transmissions. Adjustments to the modulator and/or the vacuum system, or the installation of the Superior shift kit can usually control the flaring for most vehicles. But, as the clutches and bands wear, flaring definitely becomes more common on these machines.

OK, the Superior shift kit , I assume , goes into the valve body. RIGHT ?
I have the old valve body from the old tranny, maybe I should rebuild it with the Superior shift kit. Is it Hard to rebuild the valve body?

The kit has proven successful for most folks. It's $50. and the instructions are acceptable. It's not difficult, but, cleanliness is paramount.

Do you think the plain old k1 spring and not the superior kit may help with 2/3 flare??