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4.10 to 4.88 third member change / need real life feedback

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Morning All

I am in the process of making the decision to drop gearing from the stock 4.10 to 4.88. I love my RV but my biggest fear when I drive my 1988 21 foot Dolphin / 22RE / automatic is to stall out on a steep hill. It has happened to me once and I needed a tow truck to get to the top. Truth be told I should not have attempted that hill that night. I should have just pulled over. Yet I did not and a lesson well learned.  Since then I have greater respect and understanding of the limitations of the vehicle and have adjusted my driving style accordingly. I added a tachometer and ATF temperature gauge and drive with OD locked out. I am completely happy driving 55 MPH on the flats. I just want to be able to drive with a bit less concern about what may lie around the next corner on the road. Since that time I have made the climb up to Crater Lake, (top of the torque curve in first gear), and countless other 5000 and 6000 foot climbs with 4.10 gears. How much of a difference in real life driving does 4.88 gears make? I have spent hours on line using gear ratios calculators so I think I understand the numbers. What I really need is to hear from folks who have actually made the gearing change to 4.88. Were you happy with the change? Was it worth the effort? Where there unforeseen effects of the gearing change? If you were to do it all over again would you do it again?

I welcome your feedback.


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Here ya go...


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Hi. I just made this change and I love it. 

I have a 1988 Odyssey 22 foot RV. It is the largest and probably heaviest of these units. I drove it around for about a year on the 4:10's and had more than one occasion where it just wouldnt go up some hills. In April of this year i swapped a 4:88 differential (from a 95 4-runner, $375 from a wrecking yard). My mechanic had it in in under 4 hours and I had no problems with the install afterwards. Just after getting this done, we took a trip to Alaska (all the way to Prudhoe Bay). We drove from Everett, WA through Vancouver and Squamish and past Whistler. In there were many 12% and 13% grades. I am certain I would not have made it up without the lower gears. When it drops down in to first now it will go up just about anything. As for top speed, I have the automatic and I could hardly get out it in to overdrive before. Now I can cruse along in overdrive at 60 quite comfortably.

One thing to know is that you need to adjust the speedometer. You can go through old posts on here and find Commercial Speedometer. That guy had mine in my hand 2 days after I ordered it for $80. It's been really nice to have a speedometer/odometer that works properly.

You also need to disable the overdrive high altitude lockout switch under the dash. You can just unplug it and jump the two wires together with a switch between them (I have a switch zip tied to the gearshift).

All in all I highly recommend this change. Be sure you go to the 4:88's, 4:56 would not have been enough.


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Hello all! I have a 85 Dolphin. 22re motor. I am also thinking of switching out my third member. I Currently have the 4.10. I Have been back and forth trying to decide between a 4.56 gear ratio or a 4.88. I hear both gear ratios are good reading different forum threads.  I run 205r14c tires on the rear axle instead of the common 185r14c so I think the 4.88 will be the better option. My question is, do the 4.88 third members have to be from a 4 cylinder motor also or can options from like the V6 4Runner work. I will just be buying a used 3rd member and am looking at one that is out of a 95 V6 Toyota 4x4 4Runner. If someone could inform me on the guide lines in choosing a third member that would work for my Dolphin that would be great! Thanks for the help!

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The gear change usually means changing the center pumpkin. So the v-6 pumpkin will work. You may have to change the u-joint flange.

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Yes, it looks like the 3rd member for the V6 should fit right into my rear end with no problem it seems. It being the 10 bolt pattern and all.  Just am curious that after I get it in if I'll have issues with the possibly a different spline count than my current 3rd member/axel set up or maybe an issue with my 3rd member right now being a 2 pinion and the V6 model is a 4 pinion?  Also, Are the 4 cylinder and V6 3rd members the same length? I ask just to check and see if my drive line will match back up with the new 3rd member or will it possibly be too short or two long? Thanks for all the help. 

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Axle spline should match, length is the same, u-joint flange spline the same, U-joint flange bolt pattern may be different

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You might want to read this


I made the change this May and have gone on one 869 mile trip since. Here's what I found

An update on the 4:88 rear end conversion. I just got back from an 800 mile trip to the same location I went to a year ago (Brookings to Hood River and back). The trip has been taking me about 10.5 hours one way (400 miles). This time it took a hair over 8 hours...about 8.2 hours. The reason? I could hold 3rd gear much longer on a climb AND I could stay in 2cd gear on every hill that had me dropping into first gear previously. The engine and I were quite happy.  I was using less gas petal while I was turning higher RPMs the whole trip.  I spent way less time stressing about when best to shift down because the engine was holding each gear much better. I did not have to shift down "early" and listen to the engine screaming, I could wait and shift down when the gear I was in got down to 2400~2600 RPM when the next gear down would come in at around 3300~3500 and it would pull it. I spent most of the trip turning 2800 ~ 3300 RPM. These are my figures


    44           2            3200

    50           2            3600

    50           3            2500

    55           3            2800

    60           3            3000

    65           3            3300

    65           4             2200

I was keeping up with traffic for the very first time, no sweat going 65-70, much better acceleration both passing and away from stops. The last hill to my house I was doing 18 MPH straining at 1800 RPM with the 4:10, now I was doing 28 MPH in first and could have gone faster (I don't know the RPMs becauseI was giggling so much I forgot to look at the tach). I must note that I am pulling a trailer all the time, probably just under 600# with a 250# motorcycle. So I am smiling pretty good at this point. Now for the downside... I ran 7 tanks of gas on both trips, my 4:10 average MPG was 13.36 while my 4:88 MPG was 11.72, so about a 14% decrease in MPG. However my average speed with the 4:10 was 38.09 MPH while with the 4:88 it was 48.78 MPH which is a 28% increase in speed. Divide that into your 13% MPG loss and less strain on both the driver and the drivetrain & I think I can live with the result quite well. I still found little use of the overdrive, it is just too big of a jump, at 65 MPH it would be doing 2200 RPM and I suppose you could jamb your foot down and make it go, but I still went back into 3rd at 3300 RPM.

It is a ridiculous gear ratio on the A340F 4-speed automatic transmission . If it went from 1.00 to 1.00 to maybe 0.85 4th gear might be worth something, but the 30% jump is just too much even with the 4:88 rear end.











Maybe if I was not pulling a trailer, or had a REALLY good tailwind, or my whole trip was downhill...

OH, and the driveline bolted right up to the 4 Runner Pumpkin, and the axles go right in also, and the 1995 I got had posi traction as a bonus

Today I finished adding all my miles and gallons used data into excel, almost all of it pulling a motorcycle trailer 16,165 miles averaging out to 13.56 MPG, highest MPG was 18.4 lowest was 7.08 but they were way outside the normal 12 to 15 range that most tanks gave me, you will note that 13.5 is in the center of 12-15

Edited by Lee & Joan
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Lee would you recommend the 4.88 for me in my Dolphin or go with the 4.56. I live in Arizona and am climbing a good amount of hills to get to where I need to go a lot of the time. Plus I run a little bit bigger tires in my rear end. Can't decide which one to go with but I am sure either or will be a lot better than the 4.10. 

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I would definitely use the 4:88

With your bigger tires you really don't want the 4:56, but it works well in the V6's.

The hardest part of this swap is getting the cone washers off the axle cap studs. The link to "Brake Job" shows how to do it.

There are lock cones under the nuts, a puller just makes them tighter. Put the nuts on just a bit, take a slightly larger piece of pipe and smack it with a BFH.

If things go right the cone will pop out and the nut will trap it, do it 5 more times. There 2 threaded holes in the axle flange screw in a couple of bolts then slowly and equally turn them in and pull the axle

https://www.youtube.com/watch?v=sSD03At4mOE this is how to do a brake job

you just need to watch to 45 seconds where she “smacks the crap out of them”, don’t go any farther…you just want to be able to pull the axles out enough to clear the pumpkin.

Yeah Linda ~ I should have gotten the 195's oh well next time I will know better.

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hummm, lets see. Rear axle gear set $ 200.00, bearing and seal install kit...$115.00, labor $300 minimum. No toy for 2-3 days.

Used 4.88 chunk $250-450. Takes 1 day diy... your old 4.10 chunk is worth $125-200


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It takes a well trained pro to set the gear pattern. you can't just bolt in parts and be done.

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I have been enjoying this thread. I just sourced a 4.88 geared third member in my area. It has an axle code of G144 and came off a 1995 4 Runner. Will pick it up this weekend.

Edited by 1988dolphin
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  • 1 month later...

Closing out this thread. I sourced the (G144/4.88) third member from a 1995 4 Runner located at Yank a Part auto yard in Poulsbo, WA, cost ($175). I puiled the part myself. I installed it with verbal assistance from several members of the forum. Thanks again. Very pleased with the drivability of the vehicle. I ordered, ($95) in and installed in the speedometer adapter from Commercial Speedometer in Sacramento. Additionally i installed a tachometer, and a transmission and radiator temperature gauges ($85) so I can keep a closer eye on the engine and transmission. I also bypassed the high altitude relay. Pretty cheap all things considered. Well within the ability of the average shade tree mechanic.

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