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73-87 Chevy _ GMC Trucks => Engine/Drivetrain => Topic started by: soltvedt on December 06, 2006, 05:16:00 pm

Title: 700r4 Compatibility
Post by: soltvedt on December 06, 2006, 05:16:00 pm: I have a 1991 Chevy 305 half-ton 2wd gas pickup with a bad transmission.

I was wondering how many years back I can go to find a 700r4 transmission as a bolt-on replacement.

Does anyone know?
Title: Re: 700r4 Compatibility
Post by: xtreme80 on December 06, 2006, 05:05:00 pm: On the homepage, there is a section that shows 73-87 history. This shows the 700r4 first being introduced in 1982.

Quote:
1982--New features became standard equipment on the 1982 trucks. Chevy standardized the chrome grille on all trucks and power steering on all K-series trucks. Chevy introduces the 6.2 litre GM Diesel with automatic overdrive transmission (700R4). Cheyenne model is dropped from the lineup and hood ornaments appear on the trucks. Chevy became number one in truck sales.
Title: Re: 700r4 Compatibility
Post by: roundedline on December 06, 2006, 06:17:00 pm: All 700R4's share the same casing, but the 1982-1987 were the worst ones and have a series of problems. Most have probably been rebuild by now, but the 88-92 versions have all the upgrades with no porblems. I would go up instead of down, but anything from 88-92 would work. 1993 was the start of electronic control, so some where 4L60's (700R4) and the rest were 4L60E's.
Chris Lucas
www.73-87chevytrucks.com
www.captkaoscustoms.com
Project Su
Jimmy 2WD Project
Title: Re: 700r4 Compatibility
Post by: Lt.Del on December 06, 2006, 07:18:00 pm: rebuild the one you got
SgtDel
aka "Andy"

www.delbridge.net

1979 Big 10 383 stroker
1991 Blu 'Burb 3/4 ton 4x4
Title: Re: 700r4 Compatibility
Post by: soltvedt on December 07, 2006, 10:18:00 am: I found a "700r4" in the local shopper newspaper for $50.00

The guy said he was going to put it in an '86 Caprice that he no longer has. He said it came out of a Suburban. I asked what year Suburban, and he didn't know...he only knew that it was for a 2wd vehicle.

So, that's where I am at. I figure for $50.00, it's worth attempting the swap as-is and seeing what happens.

Anyone else have any advice? Do you think it will work?

Is there a way for me to figure out what I have in my hands after I pick it up? Markings on the transmission maybe?
Title: Re: 700r4 Compatibility
Post by: VileZambonie on December 07, 2006, 06:49:00 pm: Well there are a few ways to ID the trans you bought. There is a tag on it. There is also a few markings on the case that are unique to certain years. For example the casting line on the pass side that flows upward near the cooler fittings. Let me see if I can find pics....

(http://www.geocities.com/crosley_az/700case.jpg)

(http://i6.photobucket.com/albums/y228/Sabaka454/42239942.gif)

The transmission identification code is located on the rear righthand side of the transmission above the oil pan, see figure. For code and model interpretation refer to figure. The code numbers that indicate the Julian date, tell what day of the year the transmission was built. It should be noted that the transmission model year starts in mid year. This means that the first transmission built in any model year will start with a higher Julian date.

For example; if the first transmission in 1988 was built on August 5, then the Julian date starts at 218 and goes to 365 (which is December 31). The Julian date will then drop to 001 (which is January 1), and then continue to 217 (which is August 4, 1987).
Title: Re: 700r4 Compatibility
Post by: soltvedt on December 08, 2006, 11:52:00 am: Wow, thanks for the feedback!

That's awesome. Everything I was looking for and more.

I'll look at the numbers when I get home...and I should know right where I'm at.

Now, hopefully if it's an "old" style (83-87) it will still fit right in to my 1991 truck without any mods.
Title: Re: 700r4 Compatibility
Post by: soltvedt on December 08, 2006, 11:37:00 pm: 4YP067B is the marking on my replacement transmission.

So I'm assuming it's a 1984 model. Correct?
Title: Re: 700r4 Compatibility
Post by: soltvedt on December 11, 2006, 11:04:00 am: Well, it turns out I got an "early" unit. The 700r4 I got is stamped as an 1984 model, and the torque converter from my 1991 was NOT interchangable...just as someone else warned me about. (The the transmission's shaft has 27 splines instead of 30.)

So, I had a friend stop in at the local "Advanced Auto Parts" store, and according to the guy there, they don't believe that simply ordering a 1984 torque converter (with 27 splines) will work because they said that it will not bolt up to the 1991 the flex plate. And on top of that, they also said that swapping out the flex plate will not help either because the "button" on the torque converter will not fit into the crank on the engine.

Does this all sound correct? Or is there a custom torque converter out there that someone builds that will fit? Or do I have any other options (other than changing the shaft in the transmission)?
Title: Re: 700r4 Compatibility
Post by: VileZambonie on December 11, 2006, 03:28:00 pm: You can use the other torque converter and it should have the same bolt pattern on the flexplate. Just be warned the 84 700R4 stock was WEAK!
Title: Re: 700r4 Compatibility
Post by: soltvedt on December 11, 2006, 03:31:00 pm: What "other" torque converter are you referring to?
Title: Re: 700r4 Compatibility
Post by: VileZambonie on December 11, 2006, 09:25:00 pm: Quote:
So, I had a friend stop in at the local "Advanced Auto Parts" store, and according to the guy there, they don't believe that simply ordering a 1984 torque converter (with 27 splines) will work because they said that it will not bolt up to the 1991 the flex plate.

This torque converter that they said will not work is the "other" one
Title: Re: 700r4 Compatibility
Post by: soltvedt on December 12, 2006, 01:41:00 pm: Thanks for the feedback. I am going to get a 1984 torque converter and give it a try.

I kinda thought that the parts guy was on crack.

Wish me luck!
Title: Re: 700r4 Compatibility
Post by: VileZambonie on December 12, 2006, 06:50:00 pm: Good luck. Just remember that your TV cable adjustment is critical in this transmission. Better to be a little tight on the initial adjust then too loose.
Title: Re: 700r4 Compatibility
Post by: soltvedt on December 14, 2006, 09:33:00 am: UPDATE:

Great news!

The 27 spline torque converter fit perfectly onto the transmission, and onto the flexplate, and into the crank.

I swapped the transmission tailsections to make the speedometer swap easier. I ended up having to melt the brazing that was holding the metal speedometer gear onto the output shaft, and re-braze it onto the other transmission since they were different styles. (One was plastic, one was metal.)

All things considered, the swap went perfectly. Everything was completely interchangeable.

And guess what ???
THE $50.00 1984 TRANSMISSION WORKED WITH NO REBUILD!!!
This absoluely blew my mind. I thought for sure I'd be pulling it out and rebuilding it.

Not only did I get my 3rd and 4th gears back, but it will actually drive in 4th gear at 40-45 mph. Never had that happen in 4,000 miles of driving with the old tranny. Before, I could only occasionally get it into 4th gear, and I had to really get it up to speed before it would go. That is, if it would go.

Now, onto the supposedly highly important "TV cable" adjustment. I have questions.

I left the same cable that was on the 91 truck on there, I didn't swap it out. After hooking it up to the 84 transmission, I then hooked it up top. I decided to just leave the slider right where it was...without "pressing the release button" on the adjuster. When at full throttle position, I checked the exposed metal cable by pressing on it, and there wasn't any obvious extra cable slack to be pulled. This is how I've ran the transmission so far, and when on the road during the initial tests, the shifting and downshifting "feels right".

So, my question is, if everything is shifting and downshifting at what "feels to be" the right places, is everything ok? Or what mandatory things should I check for so I don't ruin the transmission? Does anyone recommend "pressing that adjuster button" and setting it (by opening the throttle all the way) to "set" it properly? Or is that not necessary if it's currently running right?

Another rumor I've heard is that it is better to have the TV cable to tight than too loose to be "safe". What exactly will an adjuster setting of too tight "feel like" when driving the truck during downshifts? (Or what will too loose "feel like"?)

Am I just paranoid about the TV cable?
Title: Re: 700r4 Compatibility
Post by: VileZambonie on December 14, 2006, 12:54:00 pm: The 700R4's mainline pressure is derived from TV Boost and the PR valve. If the TV cable is loose line pressure will be low. With low line pressure apply devices can be overcome by tractive load and the result is slipping. It doesn't take too much slipping to allow too much clearance within a clutch pack of a weak old 700R4 and the end result is a slipping burned clutch pack. If it doesn't feel like it's upshifting too fast and it's not upshifting too late then put a witness mark on it for a good baseline. If you want to play with it from there tighten up the cable one click and see how it goes from there. You can always go back to where you started by your witness mark.