1999 K1500 Suburban transmission problem
April 28th, 2020, 1:27 AM
#1
CF Beginner
Thread Starter
Join Date: Apr 2020
Location: Southern Oregon
Posts: 2
Likes: 0
Received 0 Likes
on
0 Posts
1999 K1500 Suburban transmission problem
Thank you for your time reading about this.
350 motor and 4L60E transmission
268,000 miles
both are the originals since I got it new off the lot 21 years ago.
About two months ago, first issue started. This was completely random; never could figure out any specific pattern when it would happen, although it seemed to pop up more when first driving cold.
First issue was a hard shift from 1-2, then when shifting from 2 to what I assume is 3 it was smooth but would behave as if I suddenly was driving in sand or mud, really bogged down temporarily until I gained more speed. I wondered if maybe I was actually going from 2nd to 4th? This would come and go. Sometimes would keep happening the entire time I was driving around town, sometimes would happen then stop happening, sometimes wouldn't happen at all.
Now today second and more serious issue occurred. While at 60mph climbing up a not too steep of a grade on the freeway, I felt what I thought was a big bump in the road that I never saw coming. Exited the freeway on to a 50 mph highway. When starting from the stop sign, smooth shifting all the way to overdrive and 50mph. Then started the "big bumps" again. The suburban would suddenly and violently lose power then immediately regain it. It happened continuously but randomly with varying intervals from a couple of seconds to as long as 15 seconds between occurrences. But it happened no matter what speed I was going nor what gear I was in. After about a mile I figured I must be doing horrible damage to something by continuing driving at 50mph, so slowed to about 15 in 2nd gear and creeped home. Problem kept up all the way till I was parked in driveway. Once parked, engine idled and ran smoothly while I checked transmission fluid; looked red and smelled normal, didn't seem to be gritty at all.
Only recent changes that have occurred are that I wired up and added a new second battery and replaced the other battery as well. Also just installed a new booming sound system.
Last transmission pan/filter/gasket service was 8,000 miles and 6 months ago, after which we drove a 5000 mile scenic round trip from Oregon to Chicago and back with zero problems.
Any ideas what's actually happening based on that description? Thank you again for sharing your expertise and experienced knowledge!
350 motor and 4L60E transmission
268,000 miles
both are the originals since I got it new off the lot 21 years ago.
About two months ago, first issue started. This was completely random; never could figure out any specific pattern when it would happen, although it seemed to pop up more when first driving cold.
First issue was a hard shift from 1-2, then when shifting from 2 to what I assume is 3 it was smooth but would behave as if I suddenly was driving in sand or mud, really bogged down temporarily until I gained more speed. I wondered if maybe I was actually going from 2nd to 4th? This would come and go. Sometimes would keep happening the entire time I was driving around town, sometimes would happen then stop happening, sometimes wouldn't happen at all.
Now today second and more serious issue occurred. While at 60mph climbing up a not too steep of a grade on the freeway, I felt what I thought was a big bump in the road that I never saw coming. Exited the freeway on to a 50 mph highway. When starting from the stop sign, smooth shifting all the way to overdrive and 50mph. Then started the "big bumps" again. The suburban would suddenly and violently lose power then immediately regain it. It happened continuously but randomly with varying intervals from a couple of seconds to as long as 15 seconds between occurrences. But it happened no matter what speed I was going nor what gear I was in. After about a mile I figured I must be doing horrible damage to something by continuing driving at 50mph, so slowed to about 15 in 2nd gear and creeped home. Problem kept up all the way till I was parked in driveway. Once parked, engine idled and ran smoothly while I checked transmission fluid; looked red and smelled normal, didn't seem to be gritty at all.
Only recent changes that have occurred are that I wired up and added a new second battery and replaced the other battery as well. Also just installed a new booming sound system.
Last transmission pan/filter/gasket service was 8,000 miles and 6 months ago, after which we drove a 5000 mile scenic round trip from Oregon to Chicago and back with zero problems.
Any ideas what's actually happening based on that description? Thank you again for sharing your expertise and experienced knowledge!
Thread
Thread Starter
Forum
Replies
Last Post
benh45
1999 - 2006 (GMT800)
2
October 24th, 2017 5:08 PM
GGReactor
Tahoe & Suburban
4
August 6th, 2015 1:20 PM
slownis
Tahoe & Suburban
0
September 2nd, 2012 8:26 PM