H151 Transmission

[ArmyFJ]

I like how my H151 with the 1FZ drives. I have never needed to down shift to keep speed up hill or pass. I don’t have any experience with an H55 so I cannot compare. The shifts in the H151 have to be a little slow but nothing crazy. If you shift too quick it is a little notchy. I have 5.29s on 37s and it’s a little over geared for high speed and long distances. I’m pretty confident that probably contributes to how slow my shifts need to be. If I did it over again I probably would stay stock at 4.11s or maybe 4.56s. Not sure where you’re sitting right now with your diffs but something to consider.

 

[SoTexCruiserDoc]

I like how my H151 with the 1FZ drives. I have never needed to down shift to keep speed up hill or pass. I don’t have any experience with an H55 so I cannot compare. The shifts in the H151 have to be a little slow but nothing crazy. If you shift too quick it is a little notchy. I have 5.29s on 37s and it’s a little over geared for high speed and long distances. I’m pretty confident that probably contributes to how slow my shifts need to be. If I did it over again I probably would stay stock at 4.11s or maybe 4.56s. Not sure where you’re sitting right now with your diffs but something to consider.

I really appreciate the input. Diff gearing was going to be my next internal debate. I definitely feel like the stock 4.11s running 35’s leaves a lot to be desired on and off asphalt. Planning to stay on 35’s. Initially thought to take drivetrain in stages, starting with transmission and see how I liked it. Now thinking while it’s on the lift to go ahead and do it all, including part time. 4.56 vs 4.88 gears? I want the truck to remain “comfortable” on the asphalt at 70mph or so to get from TX to the mountain trails. Thanks again!

 

[ArmyFJ]

I really appreciate the input. Diff gearing was going to be my next internal debate. I definitely feel like the stock 4.11s running 35’s leaves a lot to be desired on and off asphalt. Planning to stay on 35’s. Initially thought to take drivetrain in stages, starting with transmission and see how I liked it. Now thinking while it’s on the lift to go ahead and do it all, including part time. 4.56 vs 4.88 gears? I want the truck to remain “comfortable” on the asphalt at 70mph or so to get from TX to the mountain trails. Thanks again!

I would highly recommend taking it in stages and see how you like it on stock gears with the transmission first. I wish I had spent more time on the stock gears on and off road before I swapped them to feel it out. I needed to get into both axles to fix some things when I first picked up my vehicle and figured I should swap the diffs at that time - that was a mistake.

I think the general rule of thumb I have seen somewhere on this forum or another is for a manual transmissions go with one less step in ratio than with an automatic - so I suppose in your case on 35s go with 4.56s instead of 4.88s. Again I would really recommend waiting to regear until you drive with the manual transmission installed.

 

[chenderson572]

View attachment 1364230
100 series with rear shift and full time case

note, the viscous clutch transfer case is not shown in any images above

Is this a stock photo... someone on Facebook is using the same Pic

 

[nestor]

Hi all,
Throwing some thoughts that I had these days about h151.
During research of making 5th gear from 0.88 to something like 5th on h152 which is something like 0.76 if I remember correctly, all that I found is that a shaft must be swapped from h152 which need some more changes.
But recently some new info from fb groups came about kit which is only for 5th. The kit is from terrain tamer and a friend alredy did some research about it.
So this is what he found: the kit is not for all h151 gearboxes, there are gearboxes h151 for 80 series and h151 for 79series, so old gearboxes integrated in 80 series can't put this kit, but the newest h151 integrated in 79 series can.
Which triggered a new search why? And what I found is different letters on top of the box.
My box have S and newest selling now have T, i'm wondering if someone knows what these letter stands for and if someone knows about this kit only for 5th?
This is my box and in internet I found new once with T