1987 4runner

Is it possible to put too much grease into the driveline? In particular, into the rear or front drive shafts?

 

Yes to the point your just pushing the grease out

Making a big mess as the grease gets slung all over things

One thing that tends to get over greased is manual hubs to the point they fail to work

 

it won't hurt the driveline, though.

ball joints can be overgreased. you don't want grease to squeeze out of the rubber seals.

 

I would imagine too much grease in the actual drive shaft could cause some imbalance which would have some negative affects. That seems like a worse case scenario though.

 

Too much grease in the slip joint of the drive shaft can "hydrolock" it, preventing it from compressing when it needs to as the suspension moves. That places extra stress on the ujoints. Too much in the ujoints comes out the seals, makes a mess, and compromises the integrity of the seals. As in most things, moderation is best.

 

Sure. Most greased joints on "modern" vehicles (yeah, I'm willing to call a 30-yr old truck modern) are protected by some sort of rubber seal. This includes the universal joints on your drive shaft, but also ball joints, tie-rod ends, etc. Even items without Zerk fittings, like CV joints.

The seal fits into a groove, and might be additionally held by a long thin spring built in to the seal. If you pump "too much" grease into that joint, you can lift the seal out of the groove. The groove is not designed to ever have the seal removed in service, so it isn't likely to drop back in by itself, and now you have your carefully greased joint open to splashing water and dirt.

Generally, the advice is to only put in so much grease that the seal "starts" to bulge slightly. Then stop.

If you have a joint that's slinging grease (like a drive shaft), clean it up and look closely at the seal. If the seal is out of the groove you MIGHT be able to push it back in, but you'd be best off replacing it (in the case of a U-joint, the bearings.)

 

I might have overfilled I greased the slip yoke until the drive shaft expanded and then grease started oozing from the slip yoke (i.e. where the splines go in). I can remove the zerk to relieve pressure. Sorry for the naive question, but where is the seal that can be damaged?

I have read in other places to fill the U-joints until the old grease is pushed out and new grease is coming out. Is this incorrect?

 

i am in the minority. you didn't hurt your driveshaft by putting in too much grease. nor the ujoints. you need to add gease to them. i've always added grease to ujoints until old grease starts to ooze out.

as noted, don't do the same for ball joints.

the driveshaft in my cj has a relief at one end, and "too much" grease oozes out if needed. it doesn't hydrolock under compression. i suspect the shafts in the 4r are the same, but i haven't pulled them to look closely.

 

@wallytoo, I am really hoping you are right ;-) Yes, the ball joints and tie rod ends I just greased till the rubber boot swells a bit.

 

OP, you are overthinking it. Your driveline is better greased often than not enough. I don't know anyone who doesnt grease slips and u joints along the driveline until they hear/see the grease. You are fine.

 

I do the same as you, so maybe not a total minority. Funny thing, my truck still has the original ball joints without grease nipples. Its only got about 95 miles, so I'm figuring greaseable ball joints are an upgrade.