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George H.
George H., ASE MasterTechnician
Category: GMC
Satisfied Customers: 18765
Experience:  15+ Years ASE Master Technician with Level 1 Certification
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I got a 84 g30 chevy moterhome with a400 at 55 mph i am tach

Customer Question

i got a 84 g30 chevy moterhome with a400 at 55 mph i am tach out at 3000 at 65 3500 is this normel
Submitted: 2 years ago.
Category: GMC
Expert:  George H. replied 2 years ago.
Hello I will help you with your question,
The TH400 is a three speed transmission so in third gear you have a direct connection from the engine to the rear differential. The differential ratio and the size of the tires will control how fast the engine turns once the transmission shifts to third.
The only way around your normal sounding high rpms is to change the ring and pinion which will make it very slow starting from stoplights or install a Gear Vendors overdrive system but that is about $2500.
Please let me know how I can help but at 55 I would not be surprised to see 3000 rpm.
Thank you