NAS D90 auto clunks when reverse selected (not driveline)

Elguru

Member
Hi Guys,

just finishing off a ‘97 D90 refurbishment.
Running great around huge parking lot (waiting for insurance) but there is a clunk clash (INTERNAL) when selecting reverse on the ZF auto.
The sump had been removed and new filter/oil replaced. The old oil was really clean pink colour and I know it hadn’t been serviced for ages so probably realistic,

Any ideas on what could be causing the noise. It’s definitely NOT the rest of the transmission or driveline as all bushes, A frame joint, etc etc are new and we have a lot of experience with manual boxes just not the auto.

Thanks.

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LRNAD90

Well-known member
Check the input shaft adapter and its interface to the input gear in the transfer case. These are very well known to have accelerated wear at low mileages. The Good news for you (having an Auto) is that the Input shaft adapter is easily replaced, unlike those of us with manual gearboxes, who need a complete rebuild of the manual gearbox with a new mainshaft..

If this is the issue, you will also need a replacement Input gear for the transfer case, make sure you get the updated version that is cross drilled for better lubrication..

More Details on the issue, if this is what is happening..

You should be able to inspect it by pulling the PTO cover and peering in with a flashlight..
 

uc4me

Well-known member
Beautiful truck..My 97 has done the 'clunk' when shifting to reverse since the truck was new. I know of other 97 owners with the same experience..assuming it's the same 'clunk'.

As I've said for years..the day it goes away is the day I'll be concerned.
 

rocky

NAS-ROW Addict
If you shift ito neutral just before the truck stops moving forward, you’ll almost certainly notice near to no clunk when shifting into reverse.
 

Elguru

Member
When it’s cold and you pause at neutral it’s much better. However when hot it doesn’t seem to make a difference.
Just “clashy” sort of noise. Not to be confused with The Clash but similarly discordant.
 
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