Completly random transmission Grinds

[Katapl]

About 4 days ago - Redline MT90 added to my redtop transmission by a shop.

So, today I added some BG to my gas and decided to run it a bit. I had decided to go for a very long drive up north. So everything is going peachy, and I've gone about 75 miles and decide to turn around and go home. As I'm pulling into 5th gear, I get a terrible hardcore grind. What the hell? It was fine on the way up. I pull to a stoplight and take off again. First, to second, to third, to *SCREEECH* fourth, to *SCREEECH* fifth. Wow, what the hell is going on?

It was fine the 75 miles up the highway. Then 4th & 5th started grinding on the way back. I garaged it and haven't tested those gears since I've gotten back. Either way, I'm scarred. What's going on?

[Eikon]

You sure the shop sealed the trans back up after adding fluid? Check the level of fluid to make sure it's ok.

You have a 240 5-spd right? Just to be clear?

Is it just the shift to 4th and the shift to 5th that grind? Once you get it in gear it's ok right?

[Katapl]

Yes, it's a 240 trans. I'm almost positive it's sealed up correctly. It was all fine until on the way home. It sometimes grinds pretty hard going into 4th and 5th, but it's fine once it's in-gear.

I'm going to take it out again and see if it grinds. I'll probably do it in a few hours.

[skydragoness]

What year is your 240? (should be in title fyi)MT-90, IMO, is too thin for S13 synchro's, I run a much thicker Redline (75w140NS) and I never get any gear grinds. You mentioned you have a SR? Usually the accompanying trannies are so beat to crap maybe the fluid change revealed some worn gears.

[Katapl]

It's an 89' 240.

EDIT: Took it down the highway and it did alright. On the way home, through the city, it grinded going into fourth, and I was only able to try once.
Modified by Katapl at 6:52 PM 11/15/2006

[rogoman]

Make sure the transmission oil is at the full level; open the fill plug and put your finger into the hole to check for presence of oil.

If the oil level is OK, then the synchronizers may be worn.