Slipping And Bump?

[J_C]

First time ever, I put my '98 with 4.0L SOHC and 5R55E into reverse, backed down a driveway, put it in drive, and it only crawled along forward so I gave it a bit of gas (it was cold, just started a minute ago at 30F ambient temperature) and engine revved slightly but not with a normal increase in forward drive, then felt a bump and it caught and drove normal for the rest of the drive.

It almost felt like the bump came from the back end but surely this is transmission related? What am I probably looking at here? Vehicle only has ~105K mi. on it but most of those in recent years were short trips so could have more wear per mileage than normal, just not heat related since it hardly ever gets up to temp.

I'm not getting any dash/trouble-codes (yet?).

 

[wollimann]

I'm not getting any dash/trouble-codes (yet?).

Hope that for you and for the future.
On the other hand everyone knows about the temperature issues,
caused by a thermostatic bypass valve located inside the valve body.
So bands, servo pistons, clutch plates, seals overheat, oil get dark and smell horrible.
In europe all sohc's came with an additional transmission cooler, if it gets warm (at 70°C oil temp)
all is ok, if not tranny overheat.
Another issue are blown valve body gaskets and/or stuck valves inside the valve body.
Worn out forward servo pistons and rear piston cause problems too.
Sprag inside the tranny.... so many parts to get broken.

then felt a bump and it caught and drove normal for the rest of the drive.

If your oillevel is high enough and oil is not burned, i would not be so afraid.
Something gets oilpressure very suddenly, first gear engaged and gave the bump to the
rear limited slip differential.
The tranny has fresh red oil and fresh filter?

 

[J_C]

It had been much colder here recently, was not slipping when it was 10F yet did at 30F yesterday.

Tranny does not have fresh fluid and filter. It was changed several years ago but with so few miles being put on it, has been a long time.

It does have a transmission cooler that came with the tow package and hasn't been driven long for several years, so I doubt the fluid got cooked from heat but long term break-down could have happened. I haven't had a chance to check the fluid yet, am pretty busy with other things for the moment and it's not my daily driver.

 

[wollimann]

came with the tow package and hasn't been driven long for several years

The tow package is a good option for additional cooling (if it works fine). Daily towing halve the live span of the tranny.
If its not driven for years, not your daily driver, so maybe some parts "baked" together and need some time/warmness to work proper again.
Hope you find the time to check up the oil and the bump never will come again.

 

[J_C]

I do drive it on shorter trips a couple of times a week, or hauling something, or more often in winter snow to save more valuable vehicles from road salt damage.

It stayed cold for the next 2-1/2 weeks longer after I had it slip, and it has not done that again since that one time, fingers crossed. I do need to look at changing the ATF before long.

It would be really funny if all it was, was that there was black ice for a dozen yards at the end of my driveway that I didn't see, then wheels slipping till they made it to clean pavement and that's what the bump was. I wasn't sliding around though, any more than expected at least, so didn't seriously consider that because it only seemed to happen right after backing out and shifting from reverse into drive.