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OEM Straight-Cut Oil Pump Gears Available

[email protected]

Supporting Vendor
627
253
Oct 24, 2012
Hamilton, ON_Canada
We've found an overseas source for OEM straight-cut oil pump gears (MD121120, MD125361). We already have a good supply of the driven gear (MD125361) but had been unable to source the drive gear (MD121120) for quite a while. We've since found a source.

These things were thought to be extinct. As you can imagine, their rarity has influenced their price. Before we commit to bringing any of these in, we need to know what kind of interest there is.

Assuming we can bring them in at the cost we've been quoted, our pricing would be as follows (pricing in $CAD):
drive gear (MD121120) alone: $400
driven gear (MD125316) alone: $160
both drive & driven: $500

(At current exchange rates the above convert to approximately $285, $114 and $355 in $USD).

If you're interested at the above pricing email us at:
[email protected] or
[email protected]

Also, we are accepting deposits on these gears / gearsets.
Details here:

Preference given to those with a deposit on record.

Thank you.
 
Last edited:

1990TSIAWDTALON

Moderator
9,698
5,537
Nov 14, 2013
Independence, Kansas
Paul, the question has been asked, will the straight cut gears work in a helical cut gear oil pump case?
Thanks!
Marty
 

[email protected]

Supporting Vendor
627
253
Oct 24, 2012
Hamilton, ON_Canada
There are a few threads on this topic and it seems there's no obvious answer. Apparently, certain TSB's would suggest they can't be mixed, but I've seen reference to some knowledgeable DSMers that have successfully done it. We aren't technically knowledgeable enough to say one way or the other. Perhaps some helpful soul can reference the relevant threads.
 

1990TSIAWDTALON

Moderator
9,698
5,537
Nov 14, 2013
Independence, Kansas
When you say "new" do you mean OEM Mitsubishi new or helical cut aftermarket case new. That's the question everyone wants answers to. Can we put straight cut gears into a helical front case assembly and still have proper clearances and oil pressure?
 

dwb

Proven Member
312
157
Sep 9, 2021
Broomfield, Colorado
When you say "new" do you mean OEM Mitsubishi new or helical cut aftermarket case new. That's the question everyone wants answers to. Can we put straight cut gears into a helical front case assembly and still have proper clearances and oil pressure?
OEM 6-bolt front case. MD175762

Edit: this is the part number Mitsu switched to when the straight cut gears were discontinued.
 

1990TSIAWDTALON

Moderator
9,698
5,537
Nov 14, 2013
Independence, Kansas
Were they straight cut cases or were the superseded cases for helical gears? :hmm:
I honestly don't know so this is a great answer if the superseded pumps were helical like 91 and up.
 

1990TSIAWDTALON

Moderator
9,698
5,537
Nov 14, 2013
Independence, Kansas
I've used straight cut gears in 91+ cases for many years. I've even seen them in 2G 7 bolt cases without issues.

FWIW, according to the Mitsubishi TSB you should not mix cases.
OEM cases or aftermarket???
I'm wondering if I can use a new aftermarket (ACL) case with new straight cut gears and not have clearance problems and bad or low oil pressure or volume or what the difference is? The helical pumps I am using have seen their amount of abuse and still hold good pressure.
 

1cleangsx

Proven Member
757
657
Sep 28, 2013
Cheyenne, Wyoming
Hey Marty for what it’s worth I polished up my original 90’ straight cut gears and threw them in a new OEM case I bought last year, I don’t remember exactly what my clearances were but they were still on the tight end with the feeler gauge to fsm spec, 600 miles on the new motor and so far no issues knock on wood. As far as compatibility with the ACL I would just buy the damn gears and check the clearance, I bet it would work, as far as the MD part # difference between the OEM cases, considering those gears were 1990 only I’m sure there’s been countless builds from shops/venders over the years with those gears in either case without issue, again from what I understand the only real shining light to the straight cut gears were a longer life in an engine with the balance shafts deleted, and to anyone who claims to be able to “hear” the gears whine must have the worlds quietest dsm with their hearing aids turned all the way up because I’ve never heard them LOL
 

1cleangsx

Proven Member
757
657
Sep 28, 2013
Cheyenne, Wyoming
On most “High” power builds people delete the balance shafts, the helical gears have “axial/side loading” issues at high rpm without the balance shaft where as the straight gears don’t have that issue with an OEM stub shaft. Basically the straight cut gears are scientifically “cool” and the helical gears aren’t, hope this helps :idontknow:

One more reason the 1990 model year is somewhat of a “Good Looking” red headed step child LOL
 

MindBlowin03

20+ Year Contributor
630
72
Apr 11, 2002
Jessup, Pennsylvania
I've seen the TSB. I've never verified any of it. Couldn't we get a depth mic and just measure? What else could it be?
That's what I do when installing straight cuts into helical cases. They have always measured in spec for me.

OEM cases or aftermarket???
I'm wondering if I can use a new aftermarket (ACL) case with new straight cut gears and not have clearance problems and bad or low oil pressure or volume or what the difference is? The helical pumps I am using have seen their amount of abuse and still hold good pressure.
Always OEM except one time where I bought an OEM Hyundai case. That was in 2009 and my car made 700+up until I pulled it apart in 2019. There was significant wear on the case and gears. 12 years and maybe 10k miles with 700+ HP.
 

CrackedDSM

10+ Year Contributor
2,185
830
Dec 17, 2009
Pensacola, Florida
On most “High” power builds people delete the balance shafts, the helical gears have “axial/side loading” issues at high rpm without the balance shaft where as the straight gears don’t have that issue with an OEM stub shaft. Basically the straight cut gears are scientifically “cool” and the helical gears aren’t, hope this helps :idontknow:

People have deleted the BS for 20 years even on stock rebuilds. Lol.

But basically I’m gonna say no. Mindblowin has a good post with the side load/wear but that was after a very long time. My feelings unless they’re fact checked, are these are a novelty and not a necessity.
 

1cleangsx

Proven Member
757
657
Sep 28, 2013
Cheyenne, Wyoming
You could be right, I’m only 600 miles in on a BSD motor, my prior engine had an ACL with helical gears and had no issues, but that was with balance shafts. Im sure there’s plenty of members on here with helical, balance shaft deleted set ups that could chime in.
 

1990TSIAWDTALON

Moderator
9,698
5,537
Nov 14, 2013
Independence, Kansas
Both my Red and Blue TSI's are BSE and ACL pumps, no issues so far and I drive them a bit hard......OMG
 

CrackedDSM

10+ Year Contributor
2,185
830
Dec 17, 2009
Pensacola, Florida
You could be right, I’m only 600 miles in on a BSD motor, my prior engine had an ACL with helical gears and had no issues, but that was with balance shafts. Im sure there’s plenty of members on here with helical, balance shaft deleted set ups that could chime in.

Had a 2G pistons 1G rods 6 bolt engine(aka stock rebuild, don’t wanna say I “built” it) that actually reused the original front pump w/helical gears with unknown mileage on the pump itself, that is still running to this day. Like 8-9 years and at minimum 80k mile later. Lol.

Edit: duh. Forgot to mention it was a balance shaft deleted engine. I didn’t use a stubby shaft either, I just cut the stock one and used a long bolt to block the hole. LOL
 
Last edited:

DSMPT

DSM Wiseman
2,178
1,762
Jun 12, 2014
Japan / Mexico, Arizona
4g61 had the balance shafts deleted from factory and came with the same front case as DSM and the same straight cut gears until early 91 and the same helical gears from mid 91 ~, just like DSM.
 

[email protected]

Supporting Vendor
627
253
Oct 24, 2012
Hamilton, ON_Canada
Okay guys, we're getting ready to place our order with our supplier.
We'll take deposits on these gears until Nov 30. We'll then be placing our order with the supplier the next day (Dec 1).

We'll only be ordering gears / gear sets to match the deposits we've received, so if you're interested, now's the time to act.

Here's the link to the deposit product in our webstore:

Thank you.
 

[email protected]

Supporting Vendor
627
253
Oct 24, 2012
Hamilton, ON_Canada
Okay, we're closing down the taking of deposits and we've placed our order on the gears. We expect to have them in stock about 2 weeks from now.

For all of those who have placed deposits: thank you. We'll be in contact when the gears arrive.
 
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