4L60/700r4 delayed engagement in cold weather

[gmbellew]

1990 GMC V1500 5.7L TBI, 4L60, NP241, 3.73 gears, ~32in measured tires.

I noticed this last winter also during a big cold snap (0 degree weather) and it seemed to be worse this winter during the recent cold snap.

The transmission engages in R quickly no matter the ambient temp or transmission temp. The transmission engages in 1 quickly no matter the ambient temp or transmission temp. The transmission engages in D quickly when ambient temps are 40deg or higher.

The issue is in colder weather on a very cold start.

The transmission engages in D almost instantly (very slight delay) when ambient temps are at 30deg or so, even on an overnight sit before starting.

Below about 30deg, the engagement in D takes longer and longer as the temps drop. It only does this on a very cold start (sitting overnight). At 0 degrees, engagement probably took a couple of seconds. But even in single digit deg temps, any sort of warmish start and it engages in D quickly again.

No other issues with shifting, TCC lockup, etc.

I change the fluid via pan drop a couple times a year (I’ve owned for 7 years). Fluid is never too burnt up and never seen anything unusual. Unknown rebuild or maintenance history before ownership, but overall the truck seemed to have been very well taken care of.

Anybody have any thoughts? Is this a live with it until it needs a rebuild situation? Or is there an easy, non rebuild option? I don’t work on transmissions besides simple fluid/filter, so this would be me taking it to a shop.

@NickTransmissions

 

[NickTransmissions]

Consider doing is a line pressure test to confirm/deny your pressures are within acceptable ranges for each gear position.

I’d do that first when cold then do it again when at op temp (be careful) to see what the readings are at idle, min TV and full TV - let us know what you observe.

 

[gmbellew]

Consider doing is a line pressure test to confirm/deny your pressures are within acceptable ranges for each gear position.

I’d do that first when cold then do it again when at op temp (be careful) to see what the readings are at idle, min TV and full TV - let us know what you observe.

I have a vac gauge and a fuel pressure gauge. but not one for the transmission. I dont mind buying a gauge to test pressure. Will this one do the job off Amazon-

Advanced Tool Design Model ATD-5550

do i test pressure while just shifting gears in the driveway, or do I i need to be driving to test the pressure as it goes through the gears?

 

[NickTransmissions]

I have a vac gauge and a fuel pressure gauge. but not one for the transmission. I dont mind buying a gauge to test pressure. Will this one do the job off Amazon-

Advanced Tool Design Model ATD-5550

do i test pressure while just shifting gears in the driveway, or do I i need to be driving to test the pressure as it goes through the gears?

Didnt see a hyperlink embedded but will say that as long as the top end of it's PSI scale is 300PSI it should work fine. Start at idle in Park, Rev, Drive, D3, D2 and D1 w/foot on brake - see what your base idle pressures are and go from there. You should see immediate line pressure when in park between 55-75PSI. It should then jump immediately to 90-120PSI when you shift into reverse then back down to 55-75PSI for neutral, drive and D3...Manual 2 and 1 should be anywhere between 140-185 PSI at idle, min TV (i.e. no throttle input).

 

[gmbellew]

Didnt see a hyperlink embedded but will say that as long as the top end of its PSI scale is 300PSI it should work fine. Start at idle in Park, Rev, Drive, D3, D2 and D1 w/foot on brake - see what your base idle pressures are and go from there. You should see immediate line pressure when in park between 55-75PSI. It should then jump immediately to 90-120PSI when you shift into reverse then back down to 55-75PSI for neutral, drive and D3...Manual 2 and 1 should be anywhere between 140-185 PSI at idle, min TV (i.e. no throttle input).

Cold start pressures -
Immediate pressure on start, some building during cranking even.
Park - 70psi
Reverse - 110psi
Neutral- 70psi
Over Drive - 70psi (pressure immediate and steady even though engagement felt just a little delayed. (35deg ambient temp).
Drive - 70psi
Second - 170psi, but needle fluttering 160psi - 180psi
First - same as second.

Throttle blip (maybe half throttle) in P/N yielded +110psi and the pressure increase was without any delay.

 

[NickTransmissions]

Cold start pressures -
Immediate pressure on start, some building during cranking even.
Park - 70psi
Reverse - 110psi
Neutral- 70psi
Over Drive - 70psi (pressure immediate and steady even though engagement felt just a little delayed. (35deg ambient temp).
Drive - 70psi
Second - 170psi, but needle fluttering 160psi - 180psi
First - same as second.

Throttle blip (maybe half throttle) in P/N yielded +110psi and the pressure increase was without any delay.

Those pressures look perfectly fine to me...I'd drop the pan next and see if the filter is clogged or other anomalies present themselves (burnt clutch matter in the pan, metal, etc).

 

[gmbellew]

Those pressures look perfectly fine to me...I'd drop the pan next and see if the filter is clogged or other anomalies present themselves (burnt clutch matter in the pan, metal, etc).

thanks. I will update when I drop the pan sometime soon!

 

[gmbellew]

Those pressures look perfectly fine to me...I'd drop the pan next and see if the filter is clogged or other anomalies present themselves (burnt clutch matter in the pan, metal, etc).

dropped the pan and put in a new filter. there was definitely clutch material in the pan, but not sure if it is crazy abnormal. it has been about 50k miles since the pan was last dropped for a filter. no other abnormalities or parts in the pan. attached is the paper towel I wiped the pan with for a little bit of a reference. between what settled out in the pan after a while and what fluid dumped out of the filter, there was more clutch material than what is shown on that paper towels for sure.

brief test drive afterward and everything is still shifting fine.

any other thoughts on the delayed OD/D engagement when shifting from a cold start in cold temps?

 

[gmbellew]

@NickTransmissions any more thoughts? anytime the transmission isn't pretty warm from driving, I can almost feel the slow engagement....it just kind of slips during the engagement. once engaged, everyhing is good.

if the transmission is warm from driving, it engages pretty quickly. R and 1 or 2 thunk in immediately at all times. anything that can be done without dropping the transmission and rebuilding? is it better to shift to 2 first to get a quicker engagement and then shift to D? what is the likely failure, and will it likely just get worse or is it likely to fail catastrophically?

 

[NickTransmissions]

@NickTransmissions any more thoughts? anytime the transmission isn't pretty warm from driving, I can almost feel the slow engagement....it just kind of slips during the engagement. once engaged, everyhing is good.

if the transmission is warm from driving, it engages pretty quickly. R and 1 or 2 thunk in immediately at all times. anything that can be done without dropping the transmission and rebuilding? is it better to shift to 2 first to get a quicker engagement and then shift to D? what is the likely failure, and will it likely just get worse or is it likely to fail catastrophically?

Could be the lip seals on your forward apply piston getting a bit hardened; they are allowing fluid to blow past when cold but becoming more supple once warmed up and start to seal properly. Same sort of explanation if you have an auxiliary valve body where the seal on the forward accumulator piston is a bit worn/hardened.

The forward accumulator piston seal (and piston) can be checked/replaced without dropping the transmission. You simply drop the auxiliary valve body itself from the case belly. If you don't have an auxiliary valve body then you'll likely need to drop the unit and completely overhaul it.

 

[gmbellew]

Thanks for the info @NickTransmissions. In the mean time, is it better to let it take its time getting into D or should I immediately shift to 2nd to get a quicker engagement?