A different differential swap - will it work

[JohnPa]

I want to swap a later J30 lsd with the 3.96 gear ratio into my 90 Q. That would give me about 75% as much change as a 4.11 swap, but I think it may be easier and cheaper.

It looks like I would only have to pull the axle flanges and drive flange and replace them with my Q flanges. Then I would replace the speedo hookup on the trans with one from a J30 and have proper speedo readings.

I think I can do this for about $250, not counting the odd parts like new diff flange seals. Great thing is, later J30 diffs are easy to come by.

Hey guys, will this work?

[Q45tech]

What are you trying to accomplish with a 3.90 that a 3.538 cannot accomplish?............... besides increasing the engine rpm 10.2% vs old speed in each gear and decreasing your highway mpg by at least 1 mpg.

Unfortunately a 10% increase in rear gear multiplied torque by this action doesn't increase acceleration by the same amount. The acelration is ~~ the cube root of the ratio difference or less than 2.5%

The quartermile will not be improved because you cannot complete quarter in 2nd gear [you will hit redline at 85 mph] and pay the penalty of the 1.0 second to shift to 3rd.You might improve zero to 60 by <0.2 second.

A less expensive method is an NICO ecu reprogram which will do the same or better to 60 and improve quarter mile by 0.4 seconds to 14.8/96 by staying in 2nd until 7300 rpm................assuning the engine is good and has adequate compression.

[bullittandy]

Maybe he wants to do it because its fun to work on cars. I just bought 2 Q's just because. I don't need 'em, won't be able to use-just because its fun.

Remember when it was fun for you?

[elwesso]

First off the J30 diff and axles are different than Q stuff. You're going to have to do a lot of mods to get it to work.

DIFF modifications IMO do not do that much... A high stall converter is a much better bang for the buck (WHY DONT PEOPLE UNDERSTAND THIS?)....

Its a lot of wasted time and effort on something that doesnt really do much of anything... Thats how I feel about any diff swap on a G50.. The Y33 guys have it a little nicer since they can take a diff from a Z32 n/a (cheap) and swap it in directly (easy)

[bullittandy]

DIFF modifications IMO do not do that much... A high stall converter is a much better bang for the buck (WHY DONT PEOPLE UNDERSTAND THIS?)....

Its a lot of wasted time and effort on something that doesnt really do much of anything... )

See my previous post.

[Q45tech]

Remember working on cars is not how I make my living, it is and always has been my hobby. Hobbies are usually fun.

But that doesn't involve creating work just to create work. I prefer the mental aspects to the physical.

[tmorgan4]

Q45tech....where do you come up the figure that the improvement in acceleration would be the cube root gearing change? That's an interesting comment I'd never heard before.

[Haitian_King]

I thought the Skyline differential swap was the best option for faster acceleration in a G50.

Is a high-stall converter something that can be added on to a stock trans? Or does it require a whole new one?

[ScottJackson]

I'm with these guys. I went from a 2.81 diff in my 540i BMW (I know, not a Q45 but close enough for a basic example) to a 3.91 diff. It helped a little bit right off the line up to about 5mph. After that, it was no faster than with the 2.81 diff. My mileage went from 21mpg to about 17-18. Not a good trade-off in my view, at all. I did the swap to get limited slip and more acceleration. I'm now looking for the lowest (numerically) limited slip diff I can find for it. I'll prob get the 3.15 ratio and call it good. A high stall converter makes a much bigger difference right off the line than the gears and you don't lose all your cruising mpg or top speed... or all the extra engine wear that comes with spinning faster while going down the road.

[superuber]

I like my 4:08 rear diff. I think it made a difference too. (sorry Wes)Not easy though

[elwesso]

IM just saying... I drove Rob's Q (now rex's, headers, exhaust, and 4.08) and I didnt think the performance was worth the effort... NOt to say it doesnt make a difference, but its far easier to use a high stall, especially for people that ARENT rick and can do everything themselves.

[Haitian_King]

Is a high-stall converter something that can be added on to a stock trans? Or does it require a whole new one?

[ScottJackson]

you can add one to the stock trans although adding a shift kit would really top it off. Sooo, anybody got a good step-by-step of how to drill the seperator plate(s) in the valve body and maybe removal of some check balls or accumulator springs that will quicken up the shifts?

[elwesso]

you cna add it to a stock trans.

3Q Jay redid his valve body, maybe he could shed some light on the situation.

IMO a hi-stall and shift kit changes how the car is... SO much more fun!

[superuber]

These are the guys I'm getting my valve body from

http://www.ipttrans.com/

doing it this winter. converter also.

[Haitian_King]

I don't know which company to go with. They both come highly recommended. Both in NJ too. Whichever one is cheapest I guess. $2275 from IPT for a complete transmission. Can't find a price on the Level 10 website.

Which one is best guys? I'm trying to get the warranty company to spring for a performance transmission, rather than a remanned. A Nissan reman is more expensive too. My company won't pay if the cost of is in excess of Blue Book Value for the car. At $5500, the factory reman is out.

Which would be the better choice? I can get a JDM transmission for my G50 with less than 65k on it for $550. Would it be better to get that, and have Level 10 or IPT do the torque converter and valve bodies? Or just buy the complete performance transmission outright?

I'd like to be able to do this soon. I get out of school for the semester next week and I'll have lots more free time. I want to get some serious work done. Then in the spring, I can concentrate on body and suspension mods.

[mtcookson]

The Q uses the RE4R03A so their listed price for a complete build is $2,975.

[Q45tech]

Don't forget the freight charges and the 5 hours swap labor.

Also the US buyers of JDM junkyards don't really know the exact mileage they just go by the 100km [62k mile] law that requires cars to be rebuilt to meet as new specs which results in many sales and junkings..

Atlanta distributers get 2-3 containers per month load with engines [ Nissan, Toyota, Honda and misc and trannies mixed and matched parts.

They clean them up to make them look good on outside and tell you what you want to hear..................this transmission came from an old school teacher who only drove on weekends............sure. They just don't know what happened in Japan.

[Haitian_King]

Damn.

I don't have to worry about the freight. The JDM shop is located about 25 minutes from my school. They also have a 3 month total warranty on the part.

The Q uses the RE4R03A so their listed price for a complete build is $2,975.

Is that for IPT or Level 10?

Which one should I go with? Or go the JDM route?

[maxnix]

OEM is $2,200 + frieght less $400 core refund + core freight.

Joe is our friend. Other things should have attention while it is out to reduce future labor costs.

[Haitian_King]

Ok.

Where did you get that number from B-Ri? The website shows $4,508.44 + $145 for shipping.

That's almost the cost of an IPT and a Level 10 (If I decided to purchase both)

Factor in the cost of labor (5 hours @ $85/hr assuming it's done at Keith's) and we're talking $5078.44. I can buy another car for that (or put a down payment on a more recent car.)

Five grand in a month isn't happening. Plus, the warranty company wouldn't cover it.

So. Back to the question. IPT, Level 10, or JDM?

[JohnPa]

What are you trying to accomplish with a 3.90 that a 3.538 cannot accomplish?............... besides increasing the engine rpm 10.2% vs old speed in each gear and decreasing your highway mpg by at least 1 mpg.

I was just hoping to get a little more 'grunt' at the lower rpms in daily driving. You just talked me out of it.............thanks.

A less expensive method is an NICO ecu reprogram which will do the same or better to 60 and improve quarter mile by 0.4 seconds to 14.8/96 by staying in 2nd until 7300 rpm................assuning the engine is good and has adequate compression.

I actually have a NICO ecu that I haven't installed. When I ordered the ecu, I also installed a later tcu with the first gear start, and swapped out my original ecu to send in for the NICO mods. Interestingly, with the 93 ecu/tcu combination it revs to about 7,200 rpm, hesitates, then shifts up. Does this seem normal? I don't drive full throttle much in Seattle proper, so I just haven't updated to the NICO ecu which I plan to do over Christmas break.

Thanks for the help

[Haitian_King]

I have a Stage II NICO ECU that I haven't installed yet as well.

[JohnPa]

you cna add it to a stock trans.

3Q Jay redid his valve body, maybe he could shed some light on the situation.

IMO a hi-stall and shift kit changes how the car is... SO much more fun!

OK, this seem like a better way to go than a diff swap to get the result I want.

However, I have the dreaded slow 2-3 upshift in cooler weather, so I just looked up the old posts in mid '05 by you and 3Q Jay (re4r03a vs. re4r01a valve body - thanks to 96Qowner for the reference ), but the thread quits before I could find out what either of you finally did to solve the problem.

So.........before I spend any time and money on a hi-stall converter and/or shift kit, I need to know how to solve my shifting issue. It is not bad........yet!

Also, if you had to choose, would you pick the hi-stall converter or the shift kit? I am assuming that you put in an IPT or equivalent shift solenoid with the reworked valve body. If not, I guess I would like to know about that too.

Thanks

[Haitian_King]

Same here. Hence the line of questioning. Didn't mean to hijack your thread with my questions.

I had wanted the Skyline differential, but with the amount of work that needs to be done, plus the cost, I don't think it'll be worth it. Maybe if I have more time/money to spend on extras. I need my transmission to be reliable everyday, as well as be fast and fun to drive.

[elwesso]

IPT from what I read is supposed to be better than level 10. The supra guys apparently like their builds better...

I would just have them rebuild your stock trans...

[Haitian_King]

but if my trans is farked, shouldn't I just replace it?

[elwesso]

Why would that matter? Theyre replacing everything if you have them rebuild it!

[Q451990]

OEM is $2,200 + frieght less $400 core refund + core freight.

http://www.trademotion.com/par...gid=1

Brian,

IOS is showing list $5152.50 / our cost $4508.44

Do you know something that's not reflected on the web site?

HK,

I have heard really good things about Level 10 for years... not sure about the other place...

[Haitian_King]

That's what I said. B-Ri must have some sort of hookup. Or is just fond of spouting incorrect information.

Why would that matter? Theyre replacing everything if you have them rebuild it!

So. The price shown on the website is what I'll be paying? How long will a rebuild take? Something that can be done in a day?