Transmission Shifting

Reply Subscribe

Thread Tools

Search this Thread

Jan 27, 2019 | 04:30 PM

skkzh

Thread Starter

New User

Joined: Oct 2010

Posts: 4

Likes: 0

Transmission Shifting

1971 Ford F100
Original 302 and C4 transmission

Truck is supposed to have 41xxx original miles. I believe this is probably correct. When I bought it a few months ago the transmission shifting very rough and down shift very quickly when accelerating.

I changed the fluid and replaced the modulator valve. I believe the fluid was the original and modulator valve too. The fluid was a little dark but did not smell in any way. The filter screen was clean and so was the pan.

now the issue. New fluid and valve and it shifts very smooth. It just shifts very soon. It will shift into 3rd gear around 20 mph. And it won’t drop back to second when I step on the accelerator. I can manually shift it into second and it downshifts very smoothly. The kick down linkage at the carb all appears to be in good condition.

I could not not find a stripe on the original modulator valve. I ordered one from Rock Auto that didn’t have a stripe listed but it came with a WHITE stripe. Will the wrong modulator valve cause the condition I’m seeing? If so, which valve do I need to order? I don’t think the one I have is adjustable.

Thanks!

Jan 27, 2019 | 05:16 PM

NumberDummy

Ford Parts Specialist

Joined: Nov 2006

Posts: 88,826

Likes: 785

From: Simi Valley, CA

C4AZ-7A377-B .. C4/C6 Modulator Valve - threaded type / .12" white stripe (Motorcraft TM-2) / Obsolete

C4: 1964/71 all Ford/Merc Passenger Cars & Econoline / 1965/71 F100/250 / 1972 F100/250 & Econoline before serial number P60,001.

C6: 1966/71 FoMoCo Passenger Cars; ditto 1972 before production date 7/17/72 // 1968/71 F100/350; ditto 1972 before serial number P60,001.

Jan 27, 2019 | 07:26 PM

skkzh

Thread Starter

New User

Joined: Oct 2010

Posts: 4

Likes: 0

Serial number on my truck is 93522...

Yes it is the thread in type.

Jan 28, 2019 | 12:20 PM

NumberDummy

Ford Parts Specialist

Joined: Nov 2006

Posts: 88,826

Likes: 785

From: Simi Valley, CA

Quote:

Originally Posted by skkzh

Serial number on my truck is 93522

Impossible!

Yes it is the thread in type.

Serial number is the last 6 digits of the VIN .. 1967/77 has a letter followed by 5 numbers.

You omitted the letter.

Jan 28, 2019 | 10:00 PM

skkzh

Thread Starter

New User

Joined: Oct 2010

Posts: 4

Likes: 0

Sorry - L93522

Jan 28, 2019 | 10:07 PM

ford390gashog

Fleet Owner

Joined: Jan 2004

Posts: 26,007

Likes: 575

From: Brentwood,CA

Your valve should be adjustable, you also need to fix your kickdown.

Apr 20, 2019 | 09:09 PM

skkzh

Thread Starter

New User

Joined: Oct 2010

Posts: 4

Likes: 0

So the issue was the check valve and spring came out when I removed the filter. I did not see it until several weeks ago. I found the spring in the bottom of my drain pan but no ball or valve. I ordered this:
https://www.rearcounter.com/D5AZ-7E3...rts191904.html

I finally installed it about 2 weeks ago. Shifts smooth now and the kick down works correctly. Thanks for the help!!!