My driveshaft at the connection with the transmission clunks like this at highway speeds and at 3 mph when turning with welded differential causing an oil leak in the rear of the transmission which can be heard in the attachment I added
IMG_1013 (1).mov

 

That does not look like the correct donor front driveshaft. I think I've seen pictures of it in another thread you made.

The right front driveshaft for an R154 in an SC is either:

-one from a 1986-1992 Supra MKIII R154 but professionally shortened by -3/4" and rebalanced. And with the SC factory center bearing swapped on.

Or

-one from a 1992-2000 SC300 Automatic that is lengthened by +50mm (aka +1.96") and rebalanced

Or

-A high quality one-piece driveshaft ideally made from lightweight but strong aluminum or from carbon fiber.

 

It is a one piece driveshaft

 

You need to get it rebalanced then. Something is off. Also what is it made from? Steel? Aluminum? Carbon fiber?

With one-piece driveshafts lighter is usually better since there is no center section with its own isolated bearing (like stock) to dampen certain vibrations at higher spinning speeds. Usually this phenomenon is noticed at highway speeds rather than lower speeds.

Aluminum and CF being much lighter this is avoided somewhat but a very good driveshaft balance is also crucial.

This won't be your solution but just for the sake of others reading the thread the factory two piece driveshaft system is VERY strong. It can handle about up to 1,000whp in most circumstances. There are two donor front driveshafts that can be modified to be totally compatible with an R154 since they both use the same spline count (from an MKIII Supra R154 shortened -3/4" and from an SC300 Automatic lengthened +50mm / +1.96").

 

The drive shaft looks too short in my opinion?

 

welded differential might be source of some of this, no? Can put stress on these components. That’s not solution to your problem but maybe part of cause. Re Oil leak in that location, if it’s atf it can be leak from main seal or transmission oil pan gasket, as two causes.

 

^^ Good point. That could also be a contributing factor. Personal opinion when it's something a lot of people do regardless of the chassis/platform but I'm not a fan of welded open differentials. Even 2-Way LSDs go out of full 100% lock when you decelerate. They just lock up to 100% when you accelerate. A welded diff is just locked all the time no matter what you do which translates stress over time through the rest of the driveline.

Although the one-piece driveshaft itself is still where I would still be investigating first.

 

gotcha, I've been trying to find a shop to balance it or two get my stock two piece extended but none of them will work on it near me so i might have to just buy a new driveshaft as the one that came with my transmission does kinda seem too short

 

^^ This may ultimately be the issue. Hopefully there is some way to salvage your current driveshaft.

I know of two good places to recommend for one piece driveshaft fabrication or modification of a combination of factory driveshafts in Florida but the freight shipping would probably be tremendous both ways.

Driftmotion does this work as a remote service (one piece driveshafts) however providing you can give them exacting measurements.

 

I haven't been on this thread in a while so I'm not sure if anyone will still reply, but could it possibly be a failing u joint? It also has noticeable vibration when getting up to speed. It is a deep rumble vibration and it gets worse as I get faster. I've tried to find driveline shops near me but it seems like it would be more worth it with my options to either get a new aluminum driveshaft or a new u joint