Anyone replaced the Vacuum Diaphragm?

[EnglishDan]

When changing from park - drive/overdrive/reverse or between reverse and drive/overdrive it takes probably a quarter of a second and then clunks on in. Whilst driving it shifts beautiful between gears. From what I've read it could be the vacuum diaphragm. The problem is, I've never done one or even know what one looks like or where to find it! But, I'm prepared to learn!
Any advice guys?

 

[BRUTUS_T_HOG]

.25 seconds for the gear to engage? sounds totally normal. it takes a split second for the spool valves in the valve body to move, then for the servo's/pistons to move and apply pressure to the gears.

 

[EnglishDan]

.25 is just a guess, but it is definitely less than a second. It is more the clunk and jerk I'm bothered about! Don't get me wrong, it is drivable - I would just like a smoother change between park & drive & reverse.

 

[Shran]

Pretty sure Brutus is right on, never had an automatic that shifted immediately and especially not between reverse and any forward gear.

Vacuum modulators are easy to replace.

 

[BRUTUS_T_HOG]

modulators are easy to replace, but will NOT help your situation. because the vacuum modulator does NOT have anything to do with the engagement of the gears

it acts as a throttle "sensor" to restrict or unrestrict a passage of oil- altering pressure in that passage. so you have several spool valves that have 2 opposing pressures on them.

on one side you have throttle pressure, and the other side you have governor pressure.

the governor is a centrifugal device that restricts or unrestricts another oil passage, in relation to vehicle speed. these opposing pressures tell your transmission when to shift and to what gear. its a balance of "engine load pressure/vehicle speed pressure"

and therefore has nothing to do with gear engagement. what you're experiencing is totally normal because when you shift into forward or reverse it puts load on the driveline which takes up any slack and causes a clunk. if you're worried the clunk is too loud and there is too much slop? crawl under the truck and shake the driveshaft to see if there is sloppy u-joints or pinion bearings. make sense? don't buy a vacuum modulator

 

[EnglishDan]

Thanks Brutus - I'll try that!