Vet76te

I think I'm needing to replace the transmission modulator valve on my '71. Stock L48 with a Turbo 400 automatic transmission.

How difficult is this job?
Anyone ever done it before?
Any tips?

Easy Mike

Not much to it. Getting access is the key.

Yes.

Expect a fluid leak when you pull it and check to see that the o-ring comes out with it.

redcruz1120

Easy. one bolt holding retainer and pull out! Make sure you don't accidentally pull the Vacuum line and disconnect it from the top.

Z06LMB

This is a ten minute job, 99.9% of this job is making room to reach or safely raise your car to get to the modulator. Expect to pay about $15 for the part, generally available wherever autoparts are sold. Leaking trans fluid is most often why most modulators are replaced.
The modulator is on the passenger side, just above the pan towards the front. There is a hold-down fork type clamp that has one small bolt holding the push-in, pull-out modulator in place. Before removing, it's a good idea to clean around modulator base and clamp with some spray brake cleaner.
Make sure you use the short section of vacuum tubing that generally comes with modulators. It's never a bad idea to check the metal tube that draws vacuum from the intake manifold or carb for dirt or clogs.
Apply a tiny smear of lube or oil to the O ring on the modulator base, insert and secure but DO NOT OVER TIGHTEN hold down clamp.
Generally, the modulators come pre-set and are adjustable from the factory.
Modulator adjustments will not have a huge impact on shift points. Mainly they work to control part throttle shifting qualities. Major moves in shift points are most easily controlled with governor weight/spring modifications. Read directions for any adjusting as some modulators are different.

Paul L

I would agree with MB.