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73-87 Chevy _ GMC Trucks => Engine/Drivetrain => Topic started by: Russ130 on September 04, 2009, 09:35:17 pm

Title: What would cause a th350 to not coast but only engine brake?
Post by: Russ130 on September 04, 2009, 09:35:17 pm

When I'm driving down the highway and let off the gas my truck immediately starts engine braking. I could be wrong but I thought all th350's coasted at highway speeds. Mine is the older non lockup type. Is there an easy fix?

Title: Re: What would cause a th350 to not coast but only engine brake?
Post by: choptop on September 04, 2009, 09:45:37 pm

I believe its because the torque convertor is still hydraulically locked when this happens. All of mine do that, Ive never really thought much about it tho.

Title: Re: What would cause a th350 to not coast but only engine brake?
Post by: VileZambonie on September 04, 2009, 11:35:16 pm

Are you sure you have all 3 shifts? Manually shift 1,2,3

Title: Re: What would cause a th350 to not coast but only engine brake?
Post by: Russ130 on September 05, 2009, 02:11:01 pm

yes it has all 3 shifts. The torque converter is a towing torque converter could that be it? I'm thinking probably not but perhaps it has to do with the shift installed. I installed both the B&M and then the Transgo kits both at the rv level.

Title: Re: What would cause a th350 to not coast but only engine brake?
Post by: Irish_Alley on September 05, 2009, 11:14:29 pm

did it just start doing it or did you do something to it?

Title: Re: What would cause a th350 to not coast but only engine brake?
Post by: okiesinmt on September 06, 2009, 01:36:56 am

I've got the same problem and I was told the intermediate sprag had gone out.

Title: Re: What would cause a th350 to not coast but only engine brake?
Post by: VileZambonie on September 06, 2009, 08:10:11 am

What do you mean you installed both? What exactly did you install?

Title: Re: What would cause a th350 to not coast but only engine brake?
Post by: Russ130 on September 06, 2009, 06:51:37 pm

Its been doing it for as long as I can remember. I installed the B&M Shift kit and then I installed the transgo kit. I was told by a local tranny shop that the transgo kit fixed issues with the tranny that the B&M kit didn't and that I should definitely install the transgo kit as well. It does coast at lower speeds but not at highway speeds. To be honest I really like the way the tranny behaves other than this one small issue. It has nice quick firm shifts that don't seem too hard and it downshifts perfectly. It engine brakes when I manually downshift as it should but not at the higher speeds like it shouldn't. Maybe I'm just wanting too much out it and should think about a 700r4 or 4l60 for it.

Title: Re: What would cause a th350 to not coast but only engine brake?
Post by: notguilty_25 on September 10, 2009, 09:51:07 pm

i spoke with a shop a while back on shift kits and they said that installing to different kits in the same tranny could be a ticking time bomb... good luck :S other than that my th350 was rebuilt over 5 years ago and sat up and until a year ago and it shifts beautiful. but it does feel like the brakes are set when i let off and highways speeds. always thought this was normal... i have wondered though...