1988 GMC C1500 Skips Second Gear

GMC C1500
Avatar
KEVOLEMON
  • MEMBER
  • 6 POSTS
hi i have a 1988 gm 1500 it has a th400 tranny and it will shift from 1st to 3rd and just skip 2nd. when i put it in 2nd gear with the selector it starts reving up and drop into 1st. i changed the fluid before this started could i have done somthing wrong.
Aug 3, 2006 at 5:25 PM
Advertisement
Avatar
BURRBRIAN
  • ✓Experienced Mechanic
  • 158 POSTS
Hi, when you changed fluid did you change the filter, too? Allthough what you are describing sounds like you might need to change your modulator valve. These aren't very costly and are easy to change out. That's what I would be looking at next. I think it just might take care of your problem. There are adjustable ones that you can set to shift earlier or later as you see fit. Also I would double check and make sure I had enough fluid but not overfull. Too much can make them act really funny sometimes, too. Good luck! :D
Aug 4, 2006 at 12:53 PM

Suggested Repair

Confirm the filter was replaced with the fluid and that the level is correct, not overfull. Next, inspect or replace the vacuum modulator valve; an adjustable unit can be used to set shift timing.

Conversation Summary

The owner of a 1988 GMC C1500 with a TH400 says it shifts from first to third and skips second. Selecting second makes the engine rev, then the transmission drops into first. The problem began after a fluid change. The expert recommends confirming the filter was changed and the fluid level is correct, then checking or replacing the modulator valve.

Add a reply
Join 2CarPros for free, one of the most advanced car repair communities on the internet. From first-time drivers to seasoned mechanics, everyone is welcome to reply, share details, and get better answers. You can add a temporary image or video first; uploads are limited to 20 MB.

Ask a new question

Frequently Asked Problems for This Vehicle