Good evening ,
I'm a brand new member, this being my first post, so please bear with me. I have followed the site for a few years and have been able solve my problems based on other peoples trouble and subsequent advice pertaining to my Expedition. You folks were life savers on a heater core replacement!
I belong to a 1985 F-150 2wd 351 HO C-6 3.00 rear axle ratio, that my wife purchased new. Although the truck has only 90k miles, there are a few issues at this point that require attention. First and foremost is a leaking rear main that has been a problem for the past few years. Having reviewed and with the help of your past threads, I should be able fix this without any major headaches. I plan on servicing the trans at this time as well and need to replace a leaking vacuum modulator. My parts guys advise me of 2 choices ,the codes being green or purple. My modulator has no remaining color codes at all due to surface rust. I was hoping somebody else may have been through this before with the same equipped truck, or might know which flavor might work better for my application.
Thanks in advance for your help. By the way, did I see a Dodge
truck advertisement on the home page last night ?

 

Welcome to FTE!

I have been through the leaking modulator valve problem. It is extremely easy to replace.

The color codes correspond to different shift characteristics. I'm going from memory, so if I'm wrong hopefully someone will correct me, but I believe the purple stripe valve gives you a soft shift and green gives you a firmer (like stock) shift.

My truck has a black stripe valve, which gives the firmest shifts. It's not harsh in daily driving, but if I really lean on it and it gets some RPMs before getting to 2nd, the gear change is pretty hard. lol.

I have changed my trans over to B&M Trick Shift (aka Type F) fluid though instead of Dex/Merc III, and I did notice that it started shifting alot firmer after I switched, as well as helping with some heat-related shifting issues. It'd be worth giving TS a try, it's worked great for me.

As far as other maintenance like a filter and fluid change, that's pretty easy too, aside from the fact that the factory didn't put in a drain plug on the pan, so you gotta be careful removing the pan so you don't get rained on. There is a drain plug on the torque convertor as well if you want to drain that too so you can do a total fluid change. It's all very straightforward with these trucks.

Between a new mod valve, new filter and new fluid, you may be surprised at how much different your truck behaves.

 

My parts book syas there is a "Diaphram Assy. (Vacuum Throttle valve)" with a Black band for use on C6 with a 460 or 400 CID engine, and a Green band for use on a C6 behind a 300, 302, or 351 CID engine.
The Green band is P/N D70Z-7A377-A (TM-43)
The Black band is P/N D4TZ-7A377-A (TM-30).

In your case the green band is what you want.

 

D7OZ-7A377-A .. Modulator Valve-Green band Single Area Diaphram (Motorcraft TM-43) / Available from Ford.

Applications: 1980/89 F100/350 300/302/351M/351W/400/420(6.9L diesel) / 1980/89 Bronco 300/302/351M/351W/400 / 1980/89 Econoline 300/302/351W/420 (6.9L diesel).

Additional applications: 1977/78 LTD/Grand Marquis 351M/400/460 / 1978/79 Econoline 300/302/351W/460 / 1978/79 F100/350 300/302/351M/400/460.

MSRP: $71.90 // FTE sponsor tousleyfordparts.com price: $47.45.

 

$47.00?!!!

I paid like $5 for mine at Autozone...

 

Thanks all, your knowledge beats the old hit & miss method. I'm sure other questions might arise as we work the bugs out this old thing. For the past few years we've only driven it to pick up mulch, lumber, ect., maybe 500-1000 miles a year. Infrequent use is creating most of our problems. Will keep you posted as to progress.Thanks again.

 

Ok, after reviewing both this post and NumbrDummy's post, I am confused. I'm rebuilding my 351M to a 400M. I assume that I have the factory issued green band modulator. The question is should I switch to the black band to have the truck perform as if the 400 was the factory motor? According to ND's post, it looks like the black band was only on the 460's.

 

You can stick a small screwdriver up inside the hose nipple and adjust them if you like. It's just like the throttle cable on the AOD's. You can have soft early shifts or late firm shifts.

 

+1 more vote for green.

Although my truck (351W) is now manual, I did have a C6 in it & installed an adjustable green modulator.
After some initial adjusting it was perfect; clean, firm shifts but not brutal........& the shift points were easy to get right.

As you install it, I would just check that you have good vacuum at the modulator hose.

 

How does the module fit (attach?) inside the transmission? Anybody have an assembly diagram?

 

They're external, at the right-hand rear of the trans.
Early versions screwed into place; later ones push in, & are held by a retainer tab & bolt.

 

See 7A377 in parts catalog pic.

 

So going from a 351m to a 400 in an F250 I should switch to the black stripe module. Accord to this.