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Username Post: 1988 K5 NV4500 Swap        (Topic#358087)
jbones515 
Poster
Posts: 10
jbones515
Reg: 12-07-15
09-17-19 10:26 AM - Post#2775711    

I've got an '88 K5 that I got tired of burning up 700R4's in. I went with a '94 NV4500 (lower granny gear) and a 32 spline NP205. Swap went well, finally got all the leaks worked out, but the stock pre-bled clutch master and slave cylinder from LMC really does not hold up to the task of moving that Centerforce dual friction clutch. So my question is, has anyone else had any luck with a custom clutch setup? I'm using the pedals from an '86 Chevy truck that bolted up to the stock NV4500 hydraulic setup, but it takes a body builder to hold it at a red light. I have no clue what the stock bore is, but from my brief research I know that the smaller the bore size, the easier it is to push. Any recommendations?

I was sent here by the guys in the Blazer forum



 
rockfangd 
"6th Year" Gold Supporting Member
Posts: 2751
rockfangd
Age: 33
Loc: Utica ny
Reg: 04-13-10
09-17-19 06:39 PM - Post#2775760    
    In response to jbones515

Ok few questions here.
Did you use the holes that should have been drilled out? 3 of them. One for the master and 2 for the studs, They have imprints on the firewall.
I ask this because of the 86 pedal assembly.
IS the body style the same?
There should be no clutch issue that I can think of unless the slave is not positioned correctly in the fork.
Is the throwout bearing installed correctly???
This is important because it is so commonly installed incorrectly.
I do not recommend holding the clutch at stops. It is hard on the clutch spring teeth and the throwout bearing. I only shift to neutral let off.
My 90 has a hard pedal but that is normal.
Hydraulic clutches do have a hard pedal as they are self adjusting.
Drooling on the swap. Wanted to do the same to my 90.
The greatest thing about the NV4500 if not rebuilt is the carbon fiber syncronizers. Not sure if the older ones had them though, but either way a very strong tranny


Old School GM fan FOREVER


Edited by rockfangd on 09-17-19 06:46 PM. Reason for edit: No reason given.

 
jbones515 
Poster
Posts: 10
jbones515
Reg: 12-07-15
09-17-19 07:22 PM - Post#2775761    
    In response to rockfangd

I did drill out the factory dimples for the master cylinder and the two bolt holes. I’m pretty certain I installed the throwout bearing correctly- Centerforce provided one with the clutch that has to be used if you want the warranty. I was just wondering if there was any worth in changing the bore size to make the truck a little more “streetable”.
Other than that, I’m extremely happy with the swap- the tranny itself was a breeze to rebuild- new synchros were a choice I was happy to spend ~$100 because it made for a very smooth shifting transmission.



 
rockfangd 
"6th Year" Gold Supporting Member
Posts: 2751
rockfangd
Age: 33
Loc: Utica ny
Reg: 04-13-10
09-17-19 08:00 PM - Post#2775765    
    In response to jbones515

The hydraulic system should be plenty fine.
That is a actual truck transmission. Bear that in mind for how it performs.
Towing, Hauling, Etc...

Old School GM fan FOREVER


 
someotherguy 
Senior Moderator
Posts: 29011
someotherguy
Age: 49
Loc: Texas
Reg: 08-01-03
09-18-19 06:34 AM - Post#2775784    
    In response to rockfangd

  • rockfangd Said:
The greatest thing about the NV4500 if not rebuilt is the carbon fiber syncronizers. Not sure if the older ones had them though, but either way a very strong tranny



All of 'em came with the carbon fiber pieces - that's the reason they absolutely require the correct trans fluid (GM # 12346190) or the Mopar equivalent. Both are re-labeled Castrol Syntorq LT (which can't easily be purchased under the Castrol name as it's an OEM product), it's formulated to help those syncros live. Without it, that transmission will soon be due for an expensive ($1K+) rebuild.

Richard

06 Silverado ISS / 06 Silverado SS / 06 300C SRT8


 
rockfangd 
"6th Year" Gold Supporting Member
Posts: 2751
rockfangd
Age: 33
Loc: Utica ny
Reg: 04-13-10
09-18-19 06:15 PM - Post#2775844    
    In response to someotherguy

That is correct.
But there is a but.
The rebuild kits are not carbon fiber, IIRC they are not available.
That being said the nice butter shifts are not as nice.
Therefore I would only rebuild it if absolutely necessary.
I have driven both original and rebuilt and there is a notable difference with the carbon fiber ones.


Old School GM fan FOREVER


 
jbones515 
Poster
Posts: 10
jbones515
Reg: 12-07-15
09-21-19 07:16 AM - Post#2776042    
    In response to rockfangd

I get that its not ever going to be a slap-shift style transmission- because it does shift slow like a lot of truck transmissions that I've used do. I was just wondering if anyone here had done a custom hydraulic setup to make the clutch pedal a little softer. I drove and worked on commercial trucks with Eaton 5- and 8-speed transmissions- none of them had clutch pedals this hard. BUT none of them had racing clutches.



 
rockfangd 
"6th Year" Gold Supporting Member
Posts: 2751
rockfangd
Age: 33
Loc: Utica ny
Reg: 04-13-10
09-21-19 09:29 AM - Post#2776052    
    In response to jbones515

Did you replace the clutch?
If you did I would break it in. The springs are very stiff when new and should break in over time

Old School GM fan FOREVER


 
jbones515 
Poster
Posts: 10
jbones515
Reg: 12-07-15
10-08-19 04:39 PM - Post#2777407    
    In response to rockfangd

It is a new clutch. I was under the impression that the spring stiffness wouldn’t ever change?



 
deckeda 
Poster
Posts: 78

Reg: 08-13-18
10-08-19 06:39 PM - Post#2777417    
    In response to jbones515

I'm with you, jbones. I wouldn't expect an automatically-adjusted clutch to alter its perceived stiffness when still unworn.

You might ask Centerforce directly about what to expect compared to stock.

Ditto re: stoplight behavior. All that does is unnecessarily wear the clutch and components. No free lunch there.

****

Weird anecdote: The one in our 2006 Accord V6 sedan is now about as stiff now as the one in our '89 C3500 ... as the Honda clutch has worn it got stiffer but ironically it engages nearly right off from the floor, about like a new one would. Rather than the clutch engaging later, slipping, and the car not ever moving, I anticipate instead one day not being able to move the shift lever into gear (something's gotta give, it's got about 240,xxx miles on it.)

'89 C3500 dually 2WD, 4-sp (SM465)


 
rockfangd 
"6th Year" Gold Supporting Member
Posts: 2751
rockfangd
Age: 33
Loc: Utica ny
Reg: 04-13-10
10-08-19 06:59 PM - Post#2777419    
    In response to deckeda

The springs on the clutch disc will be very tight when new.
As the clutch is depressed hundreds of times they will soften a little bit.
I hope that makes sense

Old School GM fan FOREVER


 
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