HawaiianRS

I'm swapping a T5 into my auto car and plan on using the disc rear from the donor car. That way I get rear discs and the better ratio. After swapping the whole rear assembly should I use the prop valve from the 83? Anything I should look out for during the swap?
Thanks

TomP

Well, your '89 uses metric (ISO) flare fittings, and the '83 axle will use standard (SAE) flare fittings... so you're gonna have a bit of trouble. You can't fit the '83 prop valve in because you'd need to change all your flare fittings at the master cylinder!

I'd definately change the prop valve, but since you can't put the '83 valve in, you'll have to buy one from GM. I think they still sells the 4-wheel-disk prop valves for $90 or so. The prop valve on 4WD doesn't do any proportioning, all 4 calipers will get equal pressure.

What you're going to need to do is adapt the rear of your car to take the standard/SAE flare hookups. Leave the whole front metric.

I think the easiest way would be to cut your front-to-rear brake tube's end off at the rear brake hose. Then obtain the correct fittings and rent a SAE brake flare tool; flare the end of the tube with a standard/SAE flare. Then you can use an '83 brake hose to connect the axle to your "adapted" front-to-rear brake tube.

Do you know about the 82-88 rear disk recall? You may need to buy the recall kit, see here for more info: https://www.thirdgen.org/techbb2/sho...threadid=78725

HawaiianRS

Thanks for the reply. I hate to ask you to hold my hand but I need to anyway. I don't even know what to ask for. Do I just go into the part store and ask for a SAE brake line fitting?

I think I get the procedure; cut off tubing just forward of metric fitting. Slide SAE fitting on, re-flare and connect to the 83 rubber line. Sounds easy enough I just need the right fitting.
What is the downside of not doing the re-call? And is there a way to find out if it was done? I'm just curious as the donor car stops well as is, and I have a lot of work to do in a short amount of time. I'll be able to replace or re-build the calipers in a month or so but doing them right now affects my budget and time line. If it's death trap imminent danger I can do it now, but I'd rather be able to spread this out over a few paychecks.

And I need a prop valve from a similar year with 4wdisc. Does the "bolt mod" work on the drum prop valve?

Not too bad, but now you've got me worried. The control arms, coils and such will swap right over............... right?

TomP

You got it, that's exactly the procedure!

That's what you'd ask for- but you'd need to find someone that knows what you're talking about, AND you'd need to see if the fitting was sold seperately. It's gotta be. And actually it might just be called a "tube nut" instead of a fitting; but the guy should (hopefully) know what you mean.

Oh- they do sell pre-flared sections of brake tubing; what I did when I did my swap was to buy a section that had the fitting I needed, cut the tube in half, and just salvaged the tube nuts. Try this; before you buy the hose, ask the guy if he has pre-flared brake tubes in stock. If he does, get the hose, then have him try to fit one of the pre-flared-tubes into the hose. That way you'll get the right sized fitting!

The SAE ones should be very easy to find... worst comes to worse, you could buy a "line lock installation kit", it should have a fitting in there somewhere. You might also look at pre-84 GM cars in junkyards; all you need is that tube nut.

The downside to not doing the recall is that the rear calipers won't work! I bought a rebuilt caliper from a local parts store and it wouldn't work at all until I put the recall kit in. You could have the dealer run the VIN of the donor car to see if the recall work was done. Since it was a safety recall (never expires), they should still have the info in their database. Definately buy the kit from gmpartsdirect (I gave the part # in that message) because it's much cheaper!

A tip that the recall work was done is to look at the brakes as they are on the donor car. Are both brake pads (two per caliper of course) touching the rotor? If they are, the calipers are probably working. When the recall work wasn't done, the piston retracts on its own- and it leaves an inch gap between the inner pad and the rotor.

I'm not sure if the "bolt mod" works with the prop valves; I never messed with mine. You could always get an adjustable prop valve, too... should be cheaper than a new GM replacement- but then you'd need to dial it in.

But everything else will work beautifully, control arms, coils, driveshaft, shocks, etc. When I did my axle, I bought the "starter kit" from http://www.por15.com - it was just enough to give my axle two coats of semi-gloss, and looked great!! (Click on their Primers Paints and Coatings link, then click on POR15 Rust Preventative. And wow, the kit's only $14.95 now... when I bought it four years ago, it was $19.95.)

Oh and http://www.classictube.com (and others) sell a "rear axle brake tube kit", with the two metal lines that go from the rubber hose to each caliper. When I fix my posi and can get my 3.73/posi/disc axle back under my car, I'm buying the stainless steel kit from them. The tube nuts like to rust to the tubes, so when you twist the tube nut, it's really snapping the tube.

TomP

Oh, a "bleeding" tip if you're going to leave the stock drum prop valve in the car (which I believe guys on here have done)... as ya know, when you disconnect the front-to-rear brake tube from the rear axle hose, the front-to-rear brake tube is gonna start dripping fluid. Have someone watch the master cylinder and make sure it doesn't empty!! Make sure they watch both sides of the reservoir, and fill it up as needed.

So, this line is going to drip as you're cutting the metric flare off and sliding the SAE tube nut on (make sure it faces the right way) and re-flaring. When you're done, it's still gonna drip- and you don't want that m/c to run dry, so-

Have the "old" 1983's rear brake hose nearby. Quick screw it onto your newly-flared front-to-rear tube. Then clamp some vise-grips in the middle of the old hose. It'll stop the drip, and you can take your time with putting the rear axle on.

Tip # 2- Got a http://www.mityvac.com brake bleeder? If ya do, try to bleed the rear axle off the car! Hook up all the lines and calipers, then hook up the NEW brake hose to the axle. Dunk the new hose into a vat of new brake fluid. Use the Mityvac to suck vacuum at each bleeder valve of each caliper until you get bubble-free fluid. When you're done with a caliper, tighten the bleeder valve up and go to the next caliper. When you're all done, pull the new hose out of the brake fluid bottle and point the new hose straight up towards the sky! Air rises so this keeps air out of your axle.

This way, when you make that final brake line connection, between the front-to-rear tube and the new brake hose, there's only a small amount of air in your system, and it'll make your life much easier.

Dry bleeding the whole length from the master cylinder down to the rear calipers absolutely sucks!!

Tip #3- I saved all my old hoses and fittings and brake tubes when I did my swap. They come in handy for "adapters" when either bleeding the brakes or replacing calipers or etc.

TomP

WOW, hey I didn't know this, but classictube.com even sells fittings!! I bet you could call/email them for the size you need! Damn that's cool... I might have to place an order soon.

They even sell brass adaptors that might do the metric-to-SAE conversion... but I don't know if you want an adapter in your system. (Personally if it were my car, I'd re-flare the line instead of using an adaptor- after all, it is the brake system we're talking about!)

HawaiianRS

Thanks for all the info Tom, it will make things alot easier. I had thought about using the VIN at the dealer but asumed they wouldn't have records that old, I'm going to call them sometime today/tomorrow.

HawaiianRS

I just got off the phone with Classic industries and they'll make me a hose with SAE on one end and Metric on the other for $30. I'm going to try and find a local shop to do it so I can avoid shipping but this seems to be a good alternative. Funny thing is I really don't want the brakes that much, I don't think they'll offer that big of an improvment but the rear has 3.73 and posi which I do want.

HawaiianRS

Called GM, they can't tell me if the work was performed but there are no open recalls on the vehicle.

TomP

That's great about Classic Industries; I didn't even know they did that kind of thing!

I felt the same way (about the brakes) when I did my 3.73/posi/disc swap from an '84 trans am- but WOW, those brakes were amazing. I miss them...

You'll know right away if you need the recall... hopefully the car already had it done. I think the '84 I pulled the rear from had the recall done- one caliper was rusted solid so I turned it in as a core to get a rebuilt caliper- but the other caliper was OK. I rebuilt the original caliper with new seals, and installed both again.

The original caliper worked great, but the "newly rebuilt" one from Pep Boys didn't stop worth a damn, and the brake pad was "away" from the rotor. When I got the rebuild kit I just installed both pistons to be sure. I kept the old pistons in case I ever had to get a rebuilt caliper again; I'd stick the old pistons in and keep the "good" pistons for myself.