Really Bad First Gear Noise

[Nailhead]

Just now got my 715 on the road after 10 months of work, and first gear makes noise. Lots of noise, loud howling noise. When I first got it going, it popped out of gear,too. It hasn't done this since I first pulled it out of the garage, however.

Is this noise endemic to this gearbox?

Please tell me that's what they all do-- I can't stomach pulling that engine right now. I guess I'm still spoiled by the M37 I owned years ago.


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[jeepdan]

Sorry to hear about your troubles.
Your going to need to remove the top of the transmission to inspect the first/reverse syncro gear.
It's the large gear shown at the back.
You can see damage to this one, which I swapped it out with a better used one.

I'm guessing that yours might be much worse





My reverse gear looked like this.


The gear on the large cluster gear that mates with these might be toast also.

[Nailhead]

Thanks Dan. Yeah, mine looks like that, but it's the better of the two gearboxes we had (the other had water in it at one time).

Can I get away with running it like this, or does it need to be dealt with right away?

[jeepdan]

First and reverse are used so little that I would live with it for now.
Have you drained the gear oil out recently?
I think the most danger would be a chip, or several fine chips getting circulated around and ruining the rest of the transmission.

I found this during the teardown, I think it was related to the loose metal in the oil.

[bullmoose]

Mines chewed up fairly bad as well, I seldom use first anyway, been that way for 10 years.... Most T98's and its younger sister the T18 are chewed up if they have been used much, 1st gear has NO synchronizer and few drivers use it properly or know to stop to get into it, therefore the damage... unless your entering the local truck pull or off-roading it will most likely be ok for some time.

Lee

[Don Cavey]

Somewhat unrelated but...

My transmission is in OK condition thankfully. When I changed the oil, it looked like coffee with cream in it. That makes sense since the top was off and water goes straight down next to the shift rod when it rains. I drained it and replaced it with new NAPA fluid, whatever is specified, I don't remember. I couldn't spring for the synthetic since I was buying a 5-gallon tub and the regular gear oil was close to a "C" note.

Now here is the result. That transmission shifted sooo much better and smoother after the oil change. I really need to do it again, I know. I also didn't find a bunch of junk in the bottom so I felt lucky.

But most importantly, you rarely use 1st gear and only occasionally use reverse so it may be better off left as is for now. Just a thought...

[jeepdan]

I would drain the oil, and feel around inside the hole
Scrape any metal out with your finger, it seems to settle down near the drain.
I highly recommend using the older GL4 formula gear oil in the transmission.
http://www.ebay.com/itm/Sta-Lube-SL2...UAAOSw8w1X373c

Maybe change the gear oil once a year, so that you keep an eye on excessive metal in the sump, and just keep driving it while looking for a spare transmission.

[jeepdan]

But most importantly, you rarely use 1st gear and only occasionally use reverse so it may be better off left as is for now. Just a thought...

You live in sunny, FLAT Florida Don, so you can get away with not using 1st. gear.

[Nailhead]

Thanks for the help everyone.

The oil has been changed once already and run for about ten miles, but it seems thinner than I'm used to 80/90 being. It's also taken on an odd color, so it's coming out.

Based on what you guys said, I'm going to leave it be for now.

[Don Cavey]

You live in sunny, FLAT Florida Don, so you can get away with not using 1st. gear.

You are right Dan. I never use first gear. For that matter, if I use first gear, the truck usually slows down so much that I end up starting in second gear!