Drop in RPM's on Freeway
June 15th, 2018, 2:09 PM
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Drop in RPM's on Freeway
Hi All.
Just hoping a few experts can point me in the right direction. I think I know what the issue is, but wanted to get some opinions.
I have a 1991 Suburban with a 454 V8 - engine rebuilt around 5K miles ago.
On the freeway - or otherwise cruising around town - if I have held my speed (with no major change in speed) for awhile and am going around 55-75, after awhile I will notice a sudden drop in engine noise and RMP. I dont have a Tach so I am just going by feel and noise. I am assuming the Overdrive is kicking in. Here is the issue; the engine seems to hold this quiet low RMP even after I have got off the freeway, stopped at a red light, and am back on surface streets. If I give it too much gas the engine will lug and shutter (it never does this except after it enters this stage). I can tell the difference because usually when I am accelerating after being stopped the engine has as usual roar, but once it enters this mode it is very quiet. I also feel like the engine is lugging because I am someone who has driven a manual for many years and it almost feels like it is in too high a gear. So all of this is to say I feel like the overdrive is staying engaged when it should disengage (if that's even the right term...)
Any ideas from the group?
Just hoping a few experts can point me in the right direction. I think I know what the issue is, but wanted to get some opinions.
I have a 1991 Suburban with a 454 V8 - engine rebuilt around 5K miles ago.
On the freeway - or otherwise cruising around town - if I have held my speed (with no major change in speed) for awhile and am going around 55-75, after awhile I will notice a sudden drop in engine noise and RMP. I dont have a Tach so I am just going by feel and noise. I am assuming the Overdrive is kicking in. Here is the issue; the engine seems to hold this quiet low RMP even after I have got off the freeway, stopped at a red light, and am back on surface streets. If I give it too much gas the engine will lug and shutter (it never does this except after it enters this stage). I can tell the difference because usually when I am accelerating after being stopped the engine has as usual roar, but once it enters this mode it is very quiet. I also feel like the engine is lugging because I am someone who has driven a manual for many years and it almost feels like it is in too high a gear. So all of this is to say I feel like the overdrive is staying engaged when it should disengage (if that's even the right term...)
Any ideas from the group?
June 16th, 2018, 4:10 PM
#2
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Just going off of what you say, that's what it sounds like. Have you had it looked at? Generally the problems I've heard of with overdrive are the vehicle not staying in overdrive when appropriate or not going in at all! But it definitely sounds like yours is either staying in overdrive or not appropriately downshifting when you come off the highway or back to stop & go driving.
June 17th, 2018, 5:26 PM
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Just going off of what you say, that's what it sounds like. Have you had it looked at? Generally the problems I've heard of with overdrive are the vehicle not staying in overdrive when appropriate or not going in at all! But it definitely sounds like yours is either staying in overdrive or not appropriately downshifting when you come off the highway or back to stop & go driving.
June 17th, 2018, 5:28 PM
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June 18th, 2018, 2:42 PM
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Thank you for the help - I'm not sure how to do that though. I couldn't find many vids/instructions on how to hook up the scan tool. I'm a weekend grease monkey, but have to admit I know nothing about Transmissions. 
Should I just take it to a reputable shop?
Should I just take it to a reputable shop?