Trans swap.. will I notice? T170rts to Nv3550

[guidoverduci]

I’ve got, what I believe, is a T170RTS 4 speed manual. It’s not very common, but I’m curious if I’d really notice a difference by upgrading to Nv3550 or AX15. If I have identified it correctly, the gear ratios are:
1st=3.0061
2nd=1.7767
3rd=1.0000
4th=0.724

Nv3550:
1st: 4.01:1
2nd: 2.32:1
3rd: 1.40:1
4th: 1.00:1
5th: .078:1

AX15:
1st: 3.83:1
2nd: 2.33:1
3rd: 1.44:1
4th: 1.00:1
5th: 0.79:1

I’ve got 4.56 gears and 35” tires. I’m just trying to determine if it’s going to be that noticeable. The extra gear should be nice, as well as a short throw shift.

 

[blubuckaroo]

Yes! Your 1st gear ratio of 3.00 isn't much better than the 2.99 of the original three speed. That's the biggest problem with the three speed. It's hard on clutches.
The 1st gear ratio of my NV3550 is 4.01. That's really pretty low, but I pull a camp trailer, and it really helps to get it rolling uphill.

 

[661buster1963]

I think 3.00 is not all that low for any needed low end grunt PROViDED the final drive ratio is 1:1 like the stock 3 speed. Since you have a 0.724 OD gear it would be like having a 4.14 first gear if final drive is 1:1

The range of gear (hi minus low) in a stock 3 speed is 2.00, your trans is 2.28. The NV 3550 is 3.22, the AX is 3.04. You can make the rest up in tire size and axle gear. The stock form is not great, yours is better, the other two offer more range but at some point you can’t use it all. I have seen guys keep 3.5 axle gears since the 4.0 low gear works for what they want, same guys can’t use OD unless they get up to 100 mph.

The NP435 has final gear at 1:1, but second is 3.24 or so so the range is 2.25.

The extra range above 2.25 is really only useful for off-road low gear wheeling AND running the highway home at 70 mph. How much of that do you have planned?
Curious what the T170 came from?

 

[guidoverduci]

I think 3.00 is not all that low for any needed low end grunt PROViDED the final drive ratio is 1:1 like the stock 3 speed. Since you have a 0.724 OD gear it would be like having a 4.14 first gear if final drive is 1:1

The range of gear (hi minus low) in a stock 3 speed is 2.00, your trans is 2.28. The NV 3550 is 3.22, the AX is 3.04. You can make the rest up in tire size and axle gear. The stock form is not great, yours is better, the other two offer more range but at some point you can’t use it all. I have seen guys keep 3.5 axle gears since the 4.0 low gear works for what they want, same guys can’t use OD unless they get up to 100 mph.

The NP435 has final gear at 1:1, but second is 3.24 or so so the range is 2.25.

The extra range above 2.25 is really only useful for off-road low gear wheeling AND running the highway home at 70 mph. How much of that do you have planned?
Curious what the T170 came from?

Good points. Not sure where the Trans came from. The PO had it put in. Paperwork for the swap says it’s T170 in 2 spots and T176 in 1 spot… I’m guessing the T176 is a typo, although I know that is a similar transmission.

This rig sees zero low gear off roading. Lives most it’s life between 45-70.

 

[walker_creek]

I did the NV3550 and 351W swap and the same time. With 33" tires and 4.88 gears it had plenty of low end and enough overdrive for Interstate.
This is a very pleasant shifting transmission.
Something to be aware of though...I could not get the transmission to fit until I put a 2" body lift on.