Bouncy transmission/ like an inertia reel, or the transmission is yoyo-ing (1 Viewer)

[Bleu62]

Hello all, in the past couple of weeks I've been experiencing a strange surging in my transmission. This has only happened in the mornings while things are still cool. Typically driving up to the same stop sign, driving uphill applying power, with not much coasting and applying brakes. The transmission seems to keep driving and then decelerate then re accelerate a few times until it calms down. The truck doesn't really seem to be affected by this, it's just a horrible racket underneath the truck, and it sorts itself out much quicker when I go to neutral. Throw some knowledge my way please.

 

[Bleu62]

I've been searching on Mud, and Google but nothing comes up with these symptoms, jw if this is an 80ism or I'm about to have catastrophic failure.

 

[scottryana]

Haven't heard of it happening. Have you checked the fluid level?

 

[Pin_Head]

What year? If you have a 93 and up, you may have a bad front hub drive flange and what you are experiencing is your viscous coupler working normally. You need to fix it before your VC siezes.

 

[Bleu62]

just checked fluid level and it looks pretty good, not to dark.
It's a 97 and I did a birf rebuild before moving and driving up to Alaska from nc last summer.
Is the highlighted the hub flange you mentioned?

 

[Pin_Head]

Yes that is the drive flange. While 95-97 flanges are stronger and less likely to wear out, they can fail. To check, just pop off the hub cap and then the grease cap covering the end of the birfield on the drive flange and then have someone drive while you check to see if the shaft is slipping in the flange because the splines are stripped out. It makes an impressive noise if the splines are stripped and the shaft is turning.

 

[Bleu62]

That makes sense, but I'm not sure it's what's happening to me. This anomaly only happens when everything is cold. I'm assuming if the teeth are stripped this would always happen. I think I'll recheck the birfs front diff and t case. I guess I'll get some seals and parts before I break into anything.

 

[Pin_Head]

I'm assuming if the teeth are stripped this would always happen.

Not really. The VC locks up after it slips for a while, so the problem will go away as you drive.

It might take all of 10 minutes to pop the grease caps off and take a look. You should hope it is a bad flange as it is cheap compared to what else can happen with the drive line. If you want a faster answer, put it in low range to lock the center differential and see if the problem goes away.

 

[Bleu62]

Will do. Was out flying the rest of the day. I'll check it after work tomorrow.

 

[Bleu62]

Sorry for the delay but it's been raining and blowing for a few days so I haven't checked yet. Crossing my fingers for something easy.

 

[Bleu62]

I've been horrible about updating this and maintenance, but with the horrible weather I didn't think the risk gain ratio was in my favor. Anyway everything seems fine w my flange and fluid levels are good. Are there any clutches in the trans that could go and theoretically cause my issues?

 

[scottryana]

Yes there are clutches and steels in the clutch packs that could theoretically burn and cause your issue, but the trans fluid would more then likely have a burnt smell. Maybe drain a qt of fluid and look for clutch material and really evaluate it.

 

[CruiseOrlando]

If you want a faster answer, put it in low range to lock the center differential and see if the problem goes away.

^^^^ do this - preferably on a dirt or gavel road - and see if your problem goes away. You can also pull the fuse for the locker ("30A Diff" I think is the label on it) - then put it back in High range. This will keep the CDL locked in high range if you don't have a CDL button.

 

[Bleu62]

Interesting. I'm going to check the trans fluid and go ahead and change my filter while I'm at it. I'll keep you all updated w what happens