Getting my 700R4 rebuilt

[SirRobyn0]

I don't know. I seem to feel the need to talk about whatever I'm doing on the truck, and the next major thing is going to be rebuilding the 700R4. A little quick back story. A week ago today I got back to the farm after work. When I pulled though the first gate I felt what felt like one single catch and heard a clunk. Honestly I thought I'd run over a rock in the drive way just right. Then backing into my parking spot it did it repeatedly. Thinking I had a gear going in the diff, I pulled the cover and found nothing wrong. The next day I drove it around locally and in 1st gear (and reverse) I could hear bearing growl when the truck was moving. As soon as it would shift into second the noise was gone. Thanks to some help from @Vbb199 & @Matt69olds the thought is that it is likely a bearing having to do with the 1st / reverse shaft and that it is likely to last another few months if not longer. I don't wanna wait until it fails though. I'd like to take this as a warning sign and get it rebuilt.

Last night I learned about, (from as trusted friend,) a trans builder, a one man operation about 40 miles from the farm. I talked with him this morning and he certainly seem to know his 700R4 stuff. At least he does compared to me, and he was much more willing to take the time to explain a few things than a lot of other places have been. I knew most of it like the later production trannys are better and that sort of thing, but still he took the time to talk about it. So I'm comfortable with this path forward. I'm not in hurry, and my wait until the farm slows down before pulling the tranny.

Ok now here's going to be my first question for ya'll. I never thought much about when my transmission was produced because it is what was in there. I just learned how to read the production year from the stamp in the pan rail on the case. It's an 1984. So it's an early production 700R4. Truck has a stock 305 will likely have a stock or near stock 350 installed when the 305 is done. I do work the truck some towing and hauling, have a huge cooler, and trans temp gauge. Am I crazy to have an early production 700R4 rebuilt, could he open it up to find it's been rebuilt and updated already? Truck has 220K on it. Let me know what you think or any specific things I should ask the builder about.

Thanks.

 

[Bextreme04]

The easiest way to do it with minimal downtime would be to get a later transmission as a core and then have the guy rebuild that. Then just take it to him to swap them one for one and be done. There's a few of them for sale for a few hundred bucks in the portland/vancouver area, so I'm sure there must be something you can get your hands on in the greater seattle area for a few hundred dollars. Its probably worth it to do that just so you can drive the truck around and keep using it while the builder works through the new unit.

 

[Vbb199]

I really wouldn't waste time on any 700r4 82-86 if you're really using it, I suppose if you're just cruising around and not putting it to work. Go ahead.


The 87-92 700r4 features an aux valve body for additional low/Rev oiling (perhaps the very reason you're experiencing trouble)

There's something additionally that's been upgraded, like a orifice diameter, or a oiling hole gets enlarged for the lower clutch center support and down area


Idk, there's a thread right on this forum actually comparing the two.


The 82-86 years are the entire reason the 700r4 has such a negative reputation

 

[SirRobyn0]

@Bextreme04 Eric, I'll be doing the R&R to save some cash on that. Good idea on the swap idea.

@Vbb199 As you might image I've done some searches on the forum for info but have not run into that thread so I will look specifically for it.

The builder did talk about swapping in different input shafts and so forth to make the older transmissions more durable so if I do not come up with something locally I will ask him about that and the associated costs. IDK if we talked valve bodies at all, it was a rather long convo, which to me is a good thing.

 

[Vbb199]

How to Identify a 700r4

First thing you want to look for is the # on the passenger side of the rear of the case just above the oil pan on the case itself. The FIRST digit denotes to year model of the transmission. NOTICE - First Digit 9 Denotes Both 1982 Model, and 1989 Model. There are 2 ways to determine a 1982...

www.gmsquarebody.com

 

[SirRobyn0]

How to Identify a 700r4

First thing you want to look for is the # on the passenger side of the rear of the case just above the oil pan on the case itself. The FIRST digit denotes to year model of the transmission. NOTICE - First Digit 9 Denotes Both 1982 Model, and 1989 Model. There are 2 ways to determine a 1982...

www.gmsquarebody.com

Thanks was getting though the drama near the end of that thread.....

 

[Turbo4whl]

According to @Matt69olds you want to find the trans that has the side casting that looks like the St. Louis arch. He has a picture. All the improvements in that trans.

Edit, I found the picture:

You must be registered for see images attach

 

[SirRobyn0]

According to @Matt69olds you want to find the trans that has the side casting that looks like the St. Louis arch. He has a picture. All the improvements in that trans.

I've read a bit about that and have seen pictures.

I want the truck & transmission to last so don't get me wrong in this statement, but I also gotta watch the budget here too. I'm going to look around to see what I can find locally for cores that are cheap. Given where I live unless I travel to get a core I think it's unlikely that I'll find one for a few hundred dollars, but I haven't looked yet so I might be wrong. Gotta start with that. If not then I'll have another talk with the builder about what he can do to beef up my unit as I was not aware of the production year of my transmission when I talked to him.

I'm also aware of the K-case but don't think that there is really any reason I'd need one of those.

 

[SirRobyn0]

So here's another little thing that I'll have to decide on after it's been rebuilt. What fluid to run?

I've always stuck with Dextron III spec-H because it was the last conventional dextron fluid and I wasn't sure if putting a synthetic fluid into an age old tranny that had never had syn in it, I just didn't think that would be a good idea.

If course I'll ask the builder, but the door is open as far as I'm concerned to running a more modern fluid which might help it handle the towing and haul better in combined with up grades.

So I guess what I'm saying is I'm open to suggestions there too.

 

[Matt69olds]

According to @Matt69olds you want to find the trans that has the side casting that looks like the St. Louis arch. He has a picture. All the improvements in that trans.

Edit, I found the picture:

You must be registered for see images attach

That’s the easiest way to identify the latest model. The next upgrade was the 4L60E, meaning no TV cable, shift solenoids, electronic pressure control, etc. However, the internals for the most part remained the same.

 

[SirRobyn0]

That’s the easiest way to identify the latest model. The next upgrade was the 4L60E, meaning no TV cable, shift solenoids, electronic pressure control, etc. However, the internals for the most part remained the same.

So let me grab your opinion too. My 84, worth upgrading or boat anchor, and I'm better off looking for a new core. If I do try to find a newer core I will not go into the convert to electronic controls so no 4L60E for me.

 

[Matt69olds]

I personally don’t care for the 86 and earlier cores. In typical GM fashion, they release a turd (think of the Cadillac 4100, the Olds 350 diesel, the first design 700 trans, the first couple years 440T4 transaxle, the list goes on) and continually improve it until it’s basically perfected, then phase it out, only to start with another turd. The 87 and up as the first major redesign to address some of the early design flaws.

The 87 and up cores are pretty easy to find, GM made millions of them.

 

[Vbb199]

Often Times people build on a K case 700r4 also.

While yes it is a 4x4 transmission, I believe the K case also features strength improvements around the bell and tailshaft housing area over the other.


It says K in a big letter at the bell, can't miss it.

 

[SirRobyn0]

Often Times people build on a K case 700r4 also.

While yes it is a 4x4 transmission, I believe the K case also features strength improvements around the bell and tailshaft housing area over the other.


It says K in a big letter at the bell, can't miss it.

My thinking is if in 40 years my case hasn't been broken then the regular case is probably fine for my uses.

 

[Vbb199]

My thinking is if in 40 years my case hasn't been broken then the regular case is probably fine for my uses.

There's probably more K case 700r4s than non K case.

You'd have to go out of your way to find a non K case.