delayed shift, is it...?

D

DavidCC

Registered
When my 94 shifts into 4th, it first raises the RPMs a significant amount, while losing power, then slides into 4th. Other shifts are OK.

Is this "flaring"?

Is this a problem in the valve body / spring assemblies or is it deeper and will it require a new tranny :/

Thanks!
David

94 Mark VIII, Black / Black
dynoed at 247.5hp / 259.7ft-lb!
 
RE: delayed shift, is it...?

From AllData:

HARSH AND/OR DELAYED 3-4 UPSHIFT

Improper fluid level.
Damaged or improperly adjusted linkage.
Throttle return spring disconnected.
Valve body bolts improperly torqued.
Valve body dirty or valves sticking.
Incorrect engine performance.
Cut or worn 3-4 accumulator piston seals.
Clogged 3-4 accumulator piston drain passage.


SLIPPING 4TH GEAR

Overdrive circuit leakage or blocked passage.
Overdrive servo piston and/or band not applying.
Overdrive band incorrectly located.
Converter damper plate and hub damaged.
Distorted direct driveshaft splines.


NO 3-4 UPSHIFTS

Low fluid level.
Damaged or improperly adjusted linkage.
Direct clutch circuit leakage.
Sticking or dirty valve body.
Distorted main control gasket.
Distorted case.
Leaking governor.

What's the fluid like? When was the last fluid change/flush? Do you have a tranny cooler?
 
RE: delayed shift, is it...?

thanks!

Accelerating at medium throttle, it shifts into 4th around 40 mph, about 2k rpm. First the rpm's rise a few hundred points, and power drops like hitting a wall. This lasts about 1.5-2 seconds. Then rpms come back down to 2k for a moment, then rpm's slide slowly down to 1.5krpms... all this under constant throttle of about 1/2 throttle.

the fluid was replaced this fall, maybe 5000 miles ago, always Merc V. I don't have a cooler. I do have the newer pan with dimple and drain plug. I haven't inspected the fluid but I will tonight.

It looks like half of those harsh upshift causes are in the valve body and the other half are outside the tranny or fluid related. That's a relief...


94 Mark VIII, Black / Black
dynoed at 247.5hp / 259.7ft-lb!
 
RE: delayed shift, is it...?

the fluid is bright red and clear with no visible stuff floating in it.


94 Mark VIII, Black / Black
dynoed at 247.5hp / 259.7ft-lb!
 
RE: delayed shift, is it...?

This info is what I found over at the TCCOA site, and put into my own summary:

Your forward clutch is releasing before the OD band is applied, putting the trans in neutral for a short time, which is bad. Or, the opposite, band applied before clutch release, called hydraulic park.

Solution: modify the valve body to reduce either situation.


Go here to see what Jerry has to say about it in detail:

http://www.tccoa.com/articles/tranny/transmission/page4.shtml
 
RE: delayed shift, is it...?

that sounds about right!

94 Mark VIII, Black / Black
dynoed at 247.5hp / 259.7ft-lb!
 
RE: delayed shift, is it...?

if this is simply a problem with the design of the valve body, why has it only just started to happen? Could it be something else?

I think I'm goinmg to take it into a tranny shop and ahve them look at it, maybe it is one of the problems listed above frm the AllData data... or maybe I get the privelege of buying a rebuilt bullet-proof frm D.R.

David


94 Mark VIII, Black / Black
dynoed at 247.5hp / 259.7ft-lb!
 
RE: delayed shift, is it...?

Hi guys,

Newbie here. I have exactly the same problem. My Mark has 100000 miles. I was wondering if the Mercon V and the accumulator replacement would cure it. Doesn't seem like it, huh? I just got the car and I don't know how long it has been going on. Don't want to get crushed at the trans shop...

Jon
 
RE: delayed shift, is it...?

IMHO if you don't know the history on the transmission, change the fluid/filter ASAP. Do not forget to drain the torque converter. Examine the condition of the fluid, filter and pan carefully. Check the accumulator to see if it has been replaced. Check the valve body bolt torque. Refill with Mercon V of 'course. Drive the vehicle a short time after the service, monitoring the fluid level and condition and of course any changes in driveability issues.

If all looks well and driveability improved, proceed with the accumulator upgrade(s) and install a transmission cooler at a minimum. Change the fluid at 15K-20K intervals.

If you still have issues, you most likely have mechanical problems with the tranny.
 
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