End result of LSD diff swap and ratio changes

[mountainhick]

First off, HUGE THANKS to TheMAN for the idea to swap in the Altezza Torsen LSD!!!!'

I just finished the rear transplant, still have the front to go (today's project). Took for a test drive in 2wd for obvious reasons. So the result: The way I drive, really no significant functional loss of torque in the hills. The acid test is getting out our driveway. There is a steep part and it is dirt/gravel, so both torque and traction are needed. My first impression is I think it actually does better on the driveway test because of the torsen. I can get a little more running start in higher 1st gear revs, then no loss of traction up the steep bit with the LSD kicking in to help.

TheMan, I think you have an auto trans, correct? I'd expect a palpable feeling of loss of torque with that tranny. But the manual has a very different first gear ratio.

So the full story about the gearing and torque results:

I had an auto tranny in her, and she totally lacked torque in 1st. Bogged down hard getting up the driveway. But, the manual trans has a very different set of gear ratios.

Auto 1st gear ratio 2.452
Manual 1st gear ratio 3.704

That is a factor of 1.51, with the manual tranny I gained that much in low end ratio in 1st gear for climbing hills! Super!

The difference between the 4.3 diff and 3.72 diff is 1.16. 51 minus 16 is still 35% higher in first gear than the starting point with the auto tranny.

On the other end, high gear,

Auto tranny ratio 0.73
manual 5th gear 0.854

That is a loss on high end ratio for highway cruising of 17%, but swapping in the 3.72 brings it back up 16%, almost to the auto trannys overdrive So final end ratio to the wheels is only 1% different than the auto tranny overdrive.

So, end result, best of both worlds, way better torque in low range than the auto trans, and just about the same ratio in high gear cruising the highway.

Now I just need to add a gear box for speedo recalibration.

[TheMAN]

Any reason why you didn't try sourcing a front LSD also?

This thread may help with the speedometer issue...
http://forum.ih8mud.com/threads/spee...change.480939/

the G57 manual trans doesn't use the same speedo gears listed in that thread, but the A46DE auto trans compatible ones might work... I still have the stock speedo gear somewhere, so pull yours out and measure the length of the shaft and let me know what it is and I'll measure mine, if it's the same length, then you can just pick one that is the right tooth count to match your axle ratios

[mountainhick]

Any reason why you didn't try sourcing a front LSD also?

This thread may help with the speedometer issue...
http://forum.ih8mud.com/threads/spee...change.480939/

the G57 manual trans doesn't use the same speedo gears listed in that thread, but the A46DE auto trans compatible ones might work... I still have the stock speedo gear somewhere, so pull yours out and measure the length of the shaft and let me know what it is and I'll measure mine, if it's the same length, then you can just pick one that is the right tooth count to match your axle ratios

One step at a time. My pockets are not that deep to do both at once, and might not really need it anyway.

I looked into replacement gears for the speedometer driven gear a while ago, even ordered what I thought might work, but no, not compatible. I might have missed something though, I dont know. It would need to be 17 tooth.

Also thought about replacing speedo drive gear in transfer case, (late 80's TV 4WD) it has 6:20 (drive:driven), the Previa SC transfer with 3.72 diff has 7:20. There is a SC at the u-pull, so it could possibly work changing the drive gear, but I didn't want the extra work to remove transfer companion flange and rear of case, and it is possible the 7 tooth gear from the SC previa won't fit the TV case. So gear box is on order.

Anyway, today's project successful, front diff is in and everything working.

[TheMAN]

time to hit up the junk yard and find some speedo gears to test

[mountainhick]

The info I found may be useful to others.

the speedo drive gears are interchangeable between Previas and at least an 86 TV 4wd transfer case.

I have/had to adapt speedo gear ratio. My speedo gear adapter works great except it sticks down too far towards the ground and is vulnerable. If it gets hit it could potentially crack the transfer case. So I am looking at other ways to change the speedo gear ratio.

It has a 20:6 ratio which is correct for 4.3 differential ratio, but I put in 3.72 diff ratio, so technically should need 20:7 which is the same as the stock Previa SC gearing.

Swapping a 7 tooth gear from AWD SC Previa into any other AWD Previa transfer case and 86 TV 4WD transfer case will work.

And that's the rest of the story...

[mountainhick]

I think this would have made sense if you had replied to your diff swap thread than making a new one so that all info is kept in one place, especially since I replied to it with a link to my thread on a different forum with all sorts of details about the speedo gears

but as far as what interchanges, I feel that more specific info is needed... the entire model code is useful to know which specific toyota to look for, and if possible, part numbers... this will allow those of us who rather buy new parts than spending time to hunt down that specific vehicle in the junk yard

Re: info on different threads, no worries, point taken if that would have worked better for you, didn't mean to confuse anything. If you want to update your thread with any of this info, please feel free. Then it will be in one place.


Re: the interchange, for me it's already a done deal, but below is the most pertinent info regarding part numbers and models.

Today I removed the companion flange and speedo drive gear to confirm, from my old donor Previa's AWD transfer case, and the same from the TV case. The only difference is the Previa has an extra seal at the companion flange's nut and the flange itself has a small machined recess for it that isn't on the TV flange

I also cross referenced the Previa's Transfer case output shafts, companion flanges and seals for both NA and SC. Same parts, all interchangable Between all AWD model Previas, so speedo drive gear 6 tooth and 7 tooth will interchange.

There's a 94 SC that I have already pulled some parts from locally and I am going back tomorrow to pull the flange and 7 tooth gear.

This is probably the most pertinent cross reference for speedometer DRIVE gear; this is for the 6 tooth gear part # 33481-26080

08/1988-12/1989 TOYOTA VAN YR2*,3* 36-10: TRANSFER GEAR Model Dates: Matching Models: Model Options: 08/1988-12/1989 YR31LG-MDEA DLX, USA, WG, 4YEC, MTM, 5F 08/1988-12/1989 YR31LG-MDEK DLX, CND, WG, 4YEC, MTM, 5F 08/1988-12/1989 YR31LG-PDEA DLX, USA, WG, 4YEC, ATM, 4FC 08/1988-12/1989 YR31LG-PDEK DLX, CND, WG, 4YEC, ATM, 4FC 08/1988-12/1989 YR31LG-PQEA LE, USA, WG, 4YEC, ATM, 4FC 08/1988-12/1989 YR31LG-PQEK LE, CND, WG, 4YEC, ATM, 4FC 08/1988-12/1989 YR32LV-MRBEK STD, CND, VAN, 4YEC, MTM, 5F, SP 08/1988-12/1989 YR32LV-PRBEA STD, USA, VAN, 4YEC, ATM, 4FC, SP 01/1990-06/1997 TOYOTA PREVIA TCR1*,2* Model Dates: Matching Models: Model Options: 01/1990-07/1992 TCR20L-REMDKA DX, USA, 2TZFE, EFI, MTM, 05S 01/1990-07/1991 TCR20L-REMDKK DX, CND, 2TZFE, EFI, MTM, 05S 08/1993-07/1995 TCR20L-RESDKA DX, USA, 2TZFE, EFI, ATM, 05S 08/1993-07/1994 TCR20L-RESDKK DX, CND, 2TZFE, EFI, ATM, 05S 08/1993-07/1995 TCR20L-RFSGKA LE, USA, 2TZFE, EFI, ATM, 07S 08/1993-07/1994 TCR20L-RFSGKK LE, CND, 2TZFE, EFI, ATM, 07S
The Previa SC, 7 tooth drive gear part number is: 33481-28030 01/1990-06/1997 TOYOTA PREVIA TCR1*,2*
Also of potential note, (at least the 94) RWD Previa speedo gear ratios are different and the drive/driven gear sets are different, I had previously ordered and have a 17 tooth driven gear, part # 33482-59015 which does not fit the driven gear assembly that plugs into the AWD and 4WD transfer cases, and the gear on the shaft is a smaller diameter. . Not interchangeable with the AWD and 4WD transfer cases. Hence my need to change the drive gear.

[timsrv]

I think this would have made sense if you had replied to your diff swap thread than making a new one so that all info is kept in one place, especially since I replied to it with a link to my thread on a different forum with all sorts of details about the speedo gears

but as far as what interchanges, I feel that more specific info is needed... the entire model code is useful to know which specific toyota to look for, and if possible, part numbers... this will allow those of us who rather buy new parts than spending time to hunt down that specific vehicle in the junk yard

I agree & I merged the threads (organization is important). Feel free to edit your original post since merging changes the context. Also, please feel free to post links to other sites & forums anywhere on TVT (if/when appropriate). Please don't hesitate to mention and post links to other sites/forums (like www.ToyotaVanPeople.com, the Yahoo Previa group, etc) as you see fit. Our mission here is to preserve these vehicles and want all posters to freely share links to any other sites that can help make that possible. I realize there are admin on other sites that talk trash about & censor other sites .............but I assure you all TVT isn't one of them (it's all about free sharing of information).

And thank you Mountainhick for all the priceless information you are sharing with us! I can tell you put a lot of time & efforts into your posts. Tim

[mountainhick]

Got the flange, drive gear and driven gear assembly for $10 at the pick a part today. A happy man here!

Also of note, the plastic driven gear has the numbers 7 and 20 molded into it. I compared to the one I am replacing, and sure enough it is marked 6 and 20. So, the 20 tooth gears themselves are different parts. Glad I got the set and not just the drive gear.