Rack swap question

[fslec]

I'm swapping the rack in my 84 from the TRW 20:1 with a newer 15:1 rack. Everything in going smoothly (basically bolt in swap) but I keep reading that I should swap the pump as well. Not sure what to believe at this point but trust you guys can answer the question. Is there really a diff? And what happens if I don't swap the pump?

Thanks
Rob

[Meotchh]

Never heard of having to swap the pump just because you go with a new rack. I could see flushing it to ensure you get the old crap fluid out of it. Where are you reading that you should replace the pump along with the rack?

[fslec]

Some of the other forums talk about the pumps being diff between a 20:1 and 15:1 ratios.
To quote one -

"You should change the pump as well. Nasty things can happen when using a 15:1 rack with a 20:1 pump.
By nasty, I mean that the pump will over-boost the rack, and can lock things up on quick transitions from one direction to another. Not fun"

I have never heard of this before so I thought best place to ask is here

[FoxBuddy]

I didn't know that the TRW rack was available in 84s I thought they transitioned them out before that. Needless to say I swapped out the TRW rack in my 82 GT a couple years ago and yes I changed the pump as well. Jack Hidley from MM chimed in on an FEP thread and "recommended" (stressed) that it should be done. I think that there is a chance under quick lock to lock steering you could run out of assist as the quicker ratio uses the pump output quicker. I don't think it's an "if you don't you're going to die as soon as you drive it" situation but it's worth the look. The newer Ford racks have different connections in them also and you will need newer hoses but I recall the pump connection sizes and hose dimensions were the same otherwise.
If I did it again and had the coin, I would go with the SN95 rack and MM hybrid shaft.
Why didn't you just get a rebuild TRW for it?

[rodster]

Never heard of this before but I suppose it makes sense if there are in fact differences between the pumps. I believe some folks on here have made the swap, maybe they will chime in.

[Kendal Coker]

I have changed them out without changing the pump. I haven't had any problems.

[fslec]

My buddy at the local NAPA store looked up pumps for the 84 and 85 and both show the same pump. I did have to replace the lines as the rack ends are diff, but that was expected. They only want $45 for a new pump but don't have it in stock so I think I'll run the old one and see what happens. I've already been running PS fluid instead of the type F for years. The PS fluid runs quiet while the Type F whines like a cat in heat.

[DaveS]

I just checked the Ford Master Parts List, the same pump is listed for '84-'86. As a matter of fact, the same pump is listed for ALL 2.3s from 10/81 through 87. Part number E6SZ-3A674-A which was replaced by F0ZZ-3AS674-A.
Hope this helps.
Dave

[rodster]

Makes it kind of difficult to swap to a 15:1 pump then doesn't it. ;)

Sounds like it could more internet mis-information?

On a related note I was just on a forum inquiring about a small engine ignition module and one 'expert' was adamant about his answer until I tore one apart to disprove his rant... that's how bad information can spread quickly.

[MikeFleming]

"I read it on the interwebs so it MUST be true, Right?"

[fslec]

The interwebs DO have much misinformation, the whole thing didn't sound right to me that's why I asked here. Thanks !!

[Jack Hidley]

I'm positive that Ford has built different model CII pumps for the slow (20:1) and fast (15:1) steering rack applications. The pumps have different cams in them to change the displaced volume per revolution. I have physically taken them apart to see this.

The document linked below has a number of pump part numbers from 2004.

http://www.fordinstallersupport.com/files/catalogs/ssd200.pdf

This document has a number of missing pages. I have tried for a long time to get a copy of it without the missing pages or an older copy of it with no luck.

Look at the bottom of page #1 (PDF page 21) for the Mustang pumps. You can see that cars with non HD suspension have a different pump than the cars with HD suspension. This is all the way back to 1980. The 15:1 racks didn't start until 1984 in the SVO or 1985 in the regular Mustang. So in the early cars there wasn't a 1:1 correspondence between steering rack ratio and HD(TRX)/non HD suspension.

The data at the above link does agree with DaveS in that it shows the same pump for all 2.3l models from 10/81 until 89 (not 87). In 1990 all of the pumps changed due to a new outlet fitting. It is possible that the SVO racks, even through they are 15:1 ratio, don't require the high volume pump as they may have a different valving or piston diameter. It would make sense that they have a more restrictive valving since the SVO is supposed to have a more performance feel than a standard Mustang and the steering system has to do a little less work due to less mass on the front tires.

[fslec]

All said and done the swap is complete leaving the original pump for the 20:1 rack. Besides the normal hose changes the 15:1 rack performs well. I never realized how much difference there is between the 2 ratios. The 20:1 steered easier but I really like the response of the 15:1

[Eyelawdoc]

Good to hear your swap went smoothly and that you're happy with the results!

[rodster]

Thanks for the update and report back!

[Raven855]

In the Mustang Performance2 handbook by Mathis, he refers to the difference between the standard pump for the 20:1 rack and the pump for the high effort 15:1 rack. Using the standard pump with the high effort rack can cause the steering to lock momentarily when attempting to change direction quickly.

[rodster]

It would be nice to have some part numbers or something externally visible to identify the different pumps.

[fslec]

In the Mustang Performance2 handbook by Mathis, he refers to the difference between the standard pump for the 20:1 rack and the pump for the high effort 15:1 rack. Using the standard pump with the high effort rack can cause the steering to lock momentarily when attempting to change direction quickly.

Raven - There might be some truth to this. I have noticed if you try to turn the wheel more than about 120 deg quickly it feels like it locks for a second and gets real hard. So far I've only noticed this in parking lots. Turn the wheel that much while driving and you would find yourself in a ditch real fast so it probably isn't a big issue.

Now the question is what pump should I look for?

[Chalky]

When I did my swap many years ago I just spec'd the same year pump as the rack I was using.