2g oil pump staight cut or helical gears

[donniekak]

You're claiming that there is a difference between front cases on the 6 bolts between the straight cut and helical gear sets? I've never heard of anything like this before and I know plenty of people running straight cuts in your average 6 bolt case. Could you elaborate on this a bit more?

There are 2 different part numbers for the 6 bolt front cases, one for straight cut gears, and one for helical.

 

[iceman510]

You're claiming that there is a difference between front cases on the 6 bolts between the straight cut and helical gear sets? I've never heard of anything like this before and I know plenty of people running straight cuts in your average 6 bolt case. Could you elaborate on this a bit more?

Not much to elaborate-but the oil pump housing (cylinder block front case in Mitsu terminology) for 6 bolt engines is a different part number for straight cut gears than for helical gears as you can see in CAPS.

MD129347 for straight
MD175762 for helical

As for what the difference is (small machining difference in the cover over that gears that goes on from the back is what I know) and if it actually affects the usage of the straight gears in a later style case, I don't know that for sure. As many have used them interchangeably, it seems to work. I have not done so, and am just reiterating that the cases are different.

 

[keltalon]

According to ASA (CAPS) they are not.

The pump cover part number changed and only later covers are to be used with the helical gears and only the straight gears are to be used in the older covers.

We all know that people are using mis-matched combinations, but there are reported failures when used like this.

Given the potential consequences of a pump failure, it's not (to me) worth the risk. I always suggest putting the proper gears in the proper covers.

The use of a turned down balance shaft makes no difference (regardless of power level).

The stub shaft is located by the back of the oil pump and it's not going off center unless the pump housing rear cover loses it's integrity.

Buyer beware

Hal

Hal I second your statements. I just couldn't find where I read not mix and match front covers and gears but I did read it. It was stated earlier that If you run the race shaft is ran then helical gears will be fine , I agree unless you can find a 1990 front cover in which it came with the straight cut gears. Thanks for your input!

There are 2 different part numbers for the 6 bolt front cases, one for straight cut gears, and one for helical.

Do you have the part numbers for which should be used?

 

[iceman510]

It's in the post right below his.

 

[DSM_GSX01]

Ok i have a question i have a 7 bolt and if i go to straight gears will i be fine? I have BSE also. Does this matter?

 

[PrimerPLus]

A little bit of an old thread but I think it's helpful.

I just rebuilt my long block. Used 7bolt. Oem front case with 1990 straight cut gears. Along with STM bse kit. After about 1200miles oil pump gears seized causing my oil pump sprocket to shatter.
I did not get any maching done to the straight cut gears or the case.
I'm about to take the motor back out and replace front case with new bse kit anf 90 straight cut gears but I will take it to be machined and deburred to make sure it will have proper clearances.

 

[Street Surgeon]

Old thread here, but I have some info to add courtesy of your GVR4 brethren. Specifically, a Mitsu TSB that says "Don't use helical gears in a straight housing, and don't use straight gears in a helical housing".

NO.: TSB-92-11-002 REVISION 2

DATE: November, 1992

MODEL: See Below

This bulletin supersedes Technical Service Bulletin # TSB-92-11-002 REVISION (Dated June, 1992) and Advance Technical information Notice # ATIN-92-11-001 (Dated July 31, 1992). Please discard the superseded TSB and ATIN.

New information includes:

- Deletion of 1983-89 2.0L Truck from Vehicles Affected list.

- Addition of new drive gear for 1983 Cordia/Tredia (1.8L and 2.0L, SOHC), 1985-87 Galant (2.4L, SOHC), 1987-90 Van/Wagon (2.4L, SOHC), and 1990-92 Truck (2.4L, SOHC).


PURPOSE

This Technical Service Bulletin describes a new oil pump/gear assembly that may reduce engine noise on some 1.6, 1.8, 2.0, and 2.4 liter 4G6-Series engines.

VEHICLES AFFECTED

1983-88 Cordia/Tredia (1.8L and 2.0L, SOHC)
1987-90 Van/Wagon (2.4L, SOHC)
1985-87 Galant (2.4L, SOHC)
1989-92 Galant (All)
1989-92 Mirage (1.6L, DOHC)
1990-92 Eclipse (2.0L, DOHC)
1990-92 Truck (2.4L, SOHC)
1992 Expo 2.4L, SOHC)


DESCRIPTION

On some vehicles equipped with the 4G6-Series engine, you may receive customer complaints of a high-pitched whining noise coming from the engine. This noise most likely originates from the engine's oil pump and is particularly noticeable during cold starting.

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To help reduce the noise, a new oil pump is available. The new pump has helical gears as opposed to the former pump's spur gears. In addition, modifications were made to the engine front case to accommodate the redesigned gears.

All 4G6-Series engines built from 6/11/91 with identification code LX8939 and up, have been assembled using the new oil pump gear set and front case assembly.

When installing the new oil pump on a vehicle, be sure to replace the drive gear, driven gear, and front case as a set. These parts are not interchangeable with the former ones.

For information concerning the replacement of the engine oil pump, refer to the applicable service manual or engine overhaul manual.

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PARTS INFORMATION

WARRANTY INFORMATION
Position Code: 121010.
Use standard warranty procedures.

 

[PrimerPLus]

So obviously don't use 1 helical gear and 1 straight cut gear. But are you saying to not use straight cut gears in a 2g 7bolt front case?

I want to be sure and do it right.

Stubby shaft with 1990 straight cut gears
What needs to be done to the gears and housing/front case

 

[Street Surgeon]

It's simple.

If you have a case that was supposed to have helical gears, use helical gears. If you have a '90 case designed for the spur gears, then use those. The cases were made/machined differently, thus using helical gears in a straight cut housing is a no-no, and so is using straight gears in a helical housing. Well, according to Mitsubishi anyway.

EDIT>>> As far as the stubby shaft goes, are we really even discussing whether or not they're "reliable" enough? People have been running them for forever and a half! People get rid of the balance shafts so they don't have to worry about them spinning a bearing, even with a turned down or machined staff you still run the risk of spinning that balance shaft bearing so why even risk it?

 

[PrimerPLus]

I was under the impression that you're supposed to use straight cut gears wirh stubby shaft due to the thrust load if you were to use the helical gears.

Are people just machining the case and gears for the straight cut gears in the helical front case/housing..

 

[gofer]

Just clearance/debur and detail the straight cut gears in the 2g front case. Start the video at 11:40, unless you want to watch all 30minutes of it.

[ame=http://www.youtube.com/watch?v=DPhyazI1fYc&feature=share&list=UUyGT_yinKL7uRiZmTjC17RQ&index=18]6&7-Bolt 4g63 Front Case & Oil Pump Rebuild - YouTube[/ame]

 

[PrimerPLus]

Thanks Gofer for clearing that up. The video is helpful too.

 

[Street Surgeon]

In Jafro's video he's using a '90 case with the '90 gearset on his 6-bolt just as a point of reference. In truth I wish/hope that you *can* use the '90 gears in a later model helical case. Can some/any engine builders or high hp (with motors that have withstood the test of time) fellas chime in with their experiences?

 

[donniekak]

Helical cut gears and thrust loading are un affected by a longer shaft with another journal bearing. If this was the case a thrust plate would be unnecessary in a turbo. What the longer shaft, and extra bearing do help with is the loading of the shaft perpendicular to the axis of rotation.
The thrust force is parallel to the axis of rotation. The only part of the system that sees any of this load is the front case, and the pump cover on the rear of the case. Unless a thrust plate, or washer(like the crankshaft) is designed into the shaft, nothing else helps absorb the thrust force.

 

[PrimerPLus]

So it doesn't make Any difference to use helical gears and a stubby shaft vs 90straight cut gears and stubby?

I seen a couple threads where peolle use the helical gears and stubby shaft. If its safe to do this then I would rather do that